Battery/amp gauge
 

Anyone have experience wiring up the factory battery gauge in a 1972 C10? I recently did a swap out from idiot lights to factory gauges, now everything works but the batt gauge.

I can't understand how these old batt. gauges operate. They basically have two hot wire hookups, one from the positive battery (passenger fender junction) and one from the red hotwire off the back of the alternator, at dash clip wires 12 and 1, respectively. I've been told the gauge measures the difference in amperage between the two. However, two hotwires don't make a circuit...there is no ground, except dash clip wire #7, which is seperate. But if you hook the gauge between positive battery and ground, you smoke the gauge.

Is there supposed to be a resistor or jumper across the back of the gauge? Mine just has this piece of varnished-looking cardboard. Also, I get continuity across both posts in the back. Does that mean the gauge is shorted, or is that the way it's supposed to be? Looks like the gauge is nothing but some fine copper wire wound around a chunk of plastic, soldered to each back post.

Any help appreciated.Thanks.

Re: Battery/amp gauge
 

Sorry I can not help. I have had 3 of these old trucks so far and none of the amp gages have worked.

I always just install a regular volt-meter under the dash.

Hopefully some one else that knows about how to hook it up will chime in.

Danny

Re: Battery/amp gauge
 

i also have same problem but did learn something related. if you have an external voltge regulator system, it needs the gen light bulb in the old dash panel or wont charge. the bulb is part of the circuit. i had to hook up the brown wire from old panel to #5 on the new panel. this will now be connected to temp light, but will allow charging system to work.

Re: Battery/amp gauge
 

I do have a voltage regulator mounted on the truck front clip frame. And the factory wiring diagrams show this is correct.

Also, it looks like there is a brown or brown/white wire from the ignition switch that ties in with the old brown generator light wire in the fusebox sandwich plug on the firewall.

OK, so let me clarify this. You swapped from idiot lights to factory gauges, and in order for your batt gauge to work you had to run the brown wire from the old dash clip wire #8 to the new dash clip wire #5? Because #5 on my diagram:http://www.gmcpaulstruckparts.com/Tech%20Tips1.htm is not used (blank), just like in the idiot light dash wire #3 wasn't used.

Also, the temp gauge wire is #6 not #5, so I'm a little confused still on your reply.

Clarification requested. Thanks again!

Re: Battery/amp gauge
 

It's an external shunt type ammeter it doesn't really measure amps it is more of a charge indicator. The charge wire is the shunt in the system and the gauge is connected at either end of the wire and is calibrated to the wires resistance make sure you fuse both wires (3-4 amp). When the ammeter sees x voltage on the battery end of the shunt (wire) it expects x voltage on the alt. end because of the shunts fixed resistance and depending on the voltage differential the ammeter moves accordinly. On smaller GM cars there was an actual shunt installed the pic below is a shunt from a chevyII.

Re: Battery/amp gauge
 

it is confusing. #5 on the new panel isnt used because it goes to a temp light. #6 is for the temp guage. a light bulb is reqired for the old external regulator to work. the new panel doesnt have a gen light, but does have a temp light that isnt used so i hooked it up there. now my system charges. as far as the charge guage i havent figured it out yet. to me you are hooking up both leads on guage to the same wire, 3 feet apart. i dont see a voltage difference.

Re: Battery/amp gauge
 

IIRC It's either or not both the brown/white wire from the ignition switch is for the gauge set up and it has a built in resistance (10 ohm) Delco recomends on models with a gen light that the reisistor wire be installed parallel to the gen light circuit but I don't think GM did this. So simply connect the existing brown wire to an ignition source but you'll have to add a 10 ohm resistor.

Re: Battery/amp gauge
 

Thats a really good idea if you connect it to pin 5 you wont need to add a resistor (bulb provides the needed resistance) and you'll have a second charge indicator. The charge wire at 30 amps will drop the voltage ~.5 volts and the gauge is a presision instument that can detect these small changes in current.

Re: Battery/amp gauge
 

So....

Neba, are you saying if I simply run a new wire from where the old brown generator light wire tied into the fusebox to the empty dash clip wire #5, my batt gauge will work?

Fixit, are you saying tie the brwn/wht ignition clip wire into what dash clip wire #? As long as you add a 10 ohm resistor?

BTW, I am using 5 amp inline fuses, surely that wouldn't affect things differently than 4 amp fuses?

Re: Battery/amp gauge
 

Neba,

I am with you. How can a guage read current difference between 2 essentially the same hotwires (batt positive & alt. red hot wire) 3 feet apart? Two hotwires never complete any kind of circuit, it seems a ground should be somewhere...but these little mickey mouse gauges go up in smaoke if you ciomplete them in a 12v DC circuit.

Re: Battery/amp gauge
 

Your gauge cluster needs be grounded for all the lights to work. Forget the resistor go with Neba's suggestion and move the brown wire to pin # 5 it's cleaner. The fuses are there to protect the printed circuit board IDK if it can handle 5 amps it probably can but dont know for sure

Re: Battery/amp gauge
 

Well guys that sounded like an easy fix.

I just ran a wire from the old generator light wire (it was twinned with the brown/white wire from the ignition clip) to pin #5 in the dash clip (originally not used for anything) and fired up the old beast. Not so much as a twitch out of the battery gauge.

Sounded too good to be true...and was, at least for me! Back to the drawing board.

BTW, does anyone know if you are suppossed to get continuity across the two copper posts on the backside of the battery gauge? Mine ohms out, and I'm wondering if that means the gauge is shorted out, or if that is what it is suppossed to do.

Re: Battery/amp gauge
 

Yeah your supposed to have continuity across the ammeter what is the size and length of the charge wire the original charge wire was 12 gauge and ~7' long. Post 3 on this thread has specs for the gauges http://67-72chevytrucks.com/vboard/s...d.php?t=360120

Re: Battery/amp gauge
 

ok, i gave up on trying to get the charge guage to work and will install an aftermarket guage under the dash. what i was trying to say was your charging system wont work if you have an external voltage regulator and switch from idiot light panel to guage panel.

Re: Battery/amp gauge
 

Oh, OK Neba. I misunderstood you.

You're saying basically that your alternator won't charge your battery if you do the dash switch unless you run the extra wire to pin #5 in the dash clip? That's pretty weird considering the alt/ hotwire is spliced into the battery positive wire run from the passenger side fender to just below the voltage regulator.

However, mine is now installed and doesn't seem to be hurting anything, so I'll leave it be just in case!

I actually have the book with the "factory" wiring diagrams, and I'm telling you the way this gauge is hooked up makes no sense whatsoever. Basically you have two hot wires run right into the dash clip at pins #1 & #12. One goes to the battery positive wire fender bolt, the other is from the alternator hotwire spliced together in a 5-wire splice by the voltage regulator.

Here's a poll question:

Does anyone have, or has anyone ever seen one of these factory gauges that actually works?

Fixit, I'd be interested to hear from you regarding the shunt system wiring from the old Chevy II's. Maybe there is a way to use that wiring scheme to properly wire these C-10 battery gauges.

Re: Battery/amp gauge
 

Your book is correct. You will have to supply the battery gauge wires and fuse them with 4 amp fuses like Fixitp said. You cannot use the no. 5 terminal as there is nothing connected to it on the gauge panel. The no, 1 and 12 terminals are for the battery gauge as you know and you will have to add them to your harness as you also know.

In order for the alternator to charge you will have to add a wire( brown ) to your harness from the ignition switch to the voltage regulator with a 30 ohm resister wired in series. That can be a light but if it blows while you're on the road then the alternator won't charge. It will also be on all the time when the engine is running.
I have added some diagrams for clarity. They show the dash wiring for both systems. The last one is the wiring for the old ammeter with the internal shunt, not sure what type the chevy II used.

Re: Battery/amp gauge
 

Thanks Vette.

The diagram of the old shunt system makes sense to me, whereas the original factory diagram for the C-10 does not. Also, your diagram lacks a voltage regulator, which is critical in the C-10 setup.

It seems that the C-10 guage is probably designed to work the same way, but minus the grounded shunt.

It seems the charging problem stems from the brown wire change-over on the gauge dashes. Basically, there is nowhere for it to go on the new setup. I cut mine off, but then retied back into it and pinned it at #5 in the dash clip, which may not be helpful at all.

I already have a brown wire from the voltage regulator (circuit #25) to the firewall sandwich plug. On the inside firewall plug, there are 2 twinned brown wires. One (brwn/wht) runs to the ignition clip and is twinned with a larger brown wire that runs to the fusebox (4A). The other is now the one I have at pin #5 in the dash clip.

So where are you saying to hook up the original brown wire (old gen. light) from #8 (idiot light) pin in the new gauge system? Are you saying solder in a resistor to this wire and run it back to the voltage regulator (twin it with brown #25?) instead of pin #5 in the dash clip?

Also, one thing I noticed in the C-10 as well as the old shunt-style diagram is the "fusible link" on the charging wire running from the 5-wire splice to the batt. positive connection on the passenger fender. The wire I have is simply a 12g solid red wire (spliced with a butt-connector) -no fuse, links, shunts, etc. I thought this "fusible link" simply meant an inline fuse was recommended here.

Re: Battery/amp gauge
 

Vette, I thought using teminal 5 was a good idea based on the diagram posted in the faq section of the printed circuit board. It shows a dotted line going from terminal 5 to the ground side of the temp light, without any foot notes I assumed that path as well as the positive side was still on the circuit board, just not being used. I dont have a circuit board to verify if it's there or not and if it isn't thanks for the correction.
http://67-72chevytrucks.com/vboard/p...pictureid=7026

72step, The brown wire which went to the alt. light is to excite the alternator and has no direct effect on the ammeter. Earlier I stated that "Delco recomends on models with a gen light that the reisistor wire be installed parallel to the gen light circuit but I don't think GM did this" and you indicated that there is a brown/white wire tied into the brown wire. If thats the case you should be good to go, I cant verify this but you can by checking the brown wire at the voltage regulator for power with the key on only also note the voltage drop to verfiy resistance. Delco recomended this to add redundancy to the chargeing system, if the alt. light ever burned out your charging system would still work not leaving you stranded.

Pole question, Mine works.

Re: Battery/amp gauge
 

72step, I posted the picture of the ChevyII shunt just to illustrate that a shunt is not just a term used to describe ammeters but that it is an actual component in the system. "electrical shunt - a conductor having low resistance in parallel with another device to divert a fraction of the current". On our trucks GM used the charge wire as the shunt because it was a fixed gauge, fixed length so it had a fixed resistance which is why I asked if you changed the wire either length or gauge would change the resistance of the shunt and effect ammeter operation. With the ChevyII as well as other smaller cars it wasn't practical to use the charge wire because the vehicle was smaller and the electrical system was configured differently and the charge wire was too short (not enough resistance) so they had to use an actual resistor. The diagram below shows the shunt wired parallel with the ammeter so whether it's the shunt or the charge wire it's still parallel with the gauge.
http://67-72chevytrucks.com/vboard/p...pictureid=7024

Re: Battery/amp gauge
 

Fixit,

I pulled the plug at the voltage reg. and checked the brown wire: no voltage with the key off. With the key on, it was 12.01 volts (brwn wire to grnd) vs. 12.49 volts at the red wire next to it on the clip to ground. So I guess there is a little resistance, but not much. I've never noticed a charging problem before, but I haven't run the truck much since the dash swap. So although the brown wire to dash pin #5 isn't doing anything, I guess it's not hurting anything either (until someone tells me where it should go!)

As to the charging wire, it is 12g red running from the five wire splice, across the top of the radiator, and finally to the passenger fender/positive batt. junction. However, its not 7', but about 61-62" (5 ft.) from the passenger fender to the 5-wire splice near the volatage regulator.

Does yours have some sort of resistor or current director near the passenger fender/ positive batt bolt? The diagram says "fusible link", but mine is just connected with a butt connector. If current flow is supposed to go from the alternator through the gauge, across the charging wire to the fender bolt/+ batt, and there is no resistor, could voltage be bleeding back through the charging wire, to 5-wire splice, then the gauge, rendering it inoperable?

Re: Battery/amp gauge
 

I'm quoting your whole post because you are right in both parts. I have a seven gauge dash that shows the lead from terminal 5 going to the second light from the left which is indeed the temperature light on the three gauge dash. I should have clarified my statement that terminal 5 goes nowhere to read that it goes to the old temperature light but that is not used on the seven gauge dash so the circuit board strip goes there and stops instead of just saying that it doesn't go anywhere. terminal 5 is a ground side terminal on the light so unless it's grounded then the light is useless. I found a dash to illustrate this as you can see the terminal 5 strip to the second light from the left. I can't understand why the conversion isn't working if the pins on the connector are changed and the ammeter wires are added as shown. This conversion has been done dozens of times with good results.

Re: Battery/amp gauge
 

If you think of the battery gauge as what it is it may help. Its a voltmeter that indicates charge or discharge of the battery.

It measures the difference in voltage at 2 points in the charging circuit. One point is close to the battery and the other is close to the alt. If the alt side is higher, indicating the alt is working, the gauge reads toward the right.

This is the same as the shunt resistor discussed above except that GM eliminated the shunt by using the wiring in the truck.

Re: Battery/amp gauge
 

Here's the definition of an external shunt ammeter which is what we have in our trucks.

An external shunt is basically a very low value resistor that is in series just as the ammeter was in the previous example, and then the ammeter is in parallel to the shunt. Basically MOST of the current goes through the shunt and only a small percentage goes through the ammeter. By knowing the resistance of the shunt and the meter, the meter is able to calculate the total current by measuring only the small current that goes through the meter. This kind of setup allows small wires to be run to the ammeter in the cockpit, and the high current to remain in the engine compartment. The danger in these setups on some old cars is there isn't a fuse on that small ammeter wire, So if the shunt is damaged or a connector breaks, it would try to flow all the current through the remaining path which is the small ammeter wire and that would melt that wire (along with whatever else it is next to).

This is the reason there are 2 small fuses in the wiring circuit on our trucks that have battery gauges. They are actually amp meters since they measure amperage differential and not volt meters because there is no connection to the negative side of the circuit.

Re: Battery/amp gauge
 

Check Murphy's law X 10 for me.:banghead:

Oh mine IS slightly to the right. Pull the whole dash panel out, it's slightly to the right, hook it up, it's slightly to the right, start the truck it's slightly to the right with never so much as a millimeter/quiver of difference no matter if connected, disconnected, started, or killed. I've checked the wiring a dozen times, it's spot on with the manual. I have voltage at the dash clip pins at both #1 & #12 when checked to ground (#7), circuit is good, gauge ohms out right, it's not shorted, etc.

I'm wondering more and more about that innocuos "fusible link" near the passenger fender on the charging wire in the wiring manual, as well as Fixit's comment about the charging wire being a certain length/resistance.

Re: Battery/amp gauge
 

Well if you check the circuit for the battery gauge wires then you can see they run from the gauge to the fender terminal and from the gauge to the three way connector of the alternator, regulator,and the battery. if you followed this then you should have a working gauge, otherwise it must be a gauge problem. I think you have seen this circuit diagram and if not I can post it for you.

Re: Battery/amp gauge
 

Sorry, but you just don't understand what you're talking about. Your last sentence, among others, proves this.

The meter that reads in amps in a shunt ammeter is still a voltmeter measuring the voltage across the shunt resistor.

Look at the battery gauge and you'll see that it will fry before anything else in the circuit.

You might want to try using a web search to learn what an actual ammeter is and how it works.

The OP may want to look into the differences in the two underhood harnesses to see if they are missing the wires needed to make the gauge work.
Look

Re: Battery/amp gauge
 

After going back and re-reading my post I discovered that I mistakenly said the shunt ammeter measures amperage differential. I meant to say voltage differential so I concede that mistake. I also maintain that the external shunt ammeter is neither a volt meter or an amp meter in the exact definition of either. It would be nice if you would point out errors instead of just saying that I don't understand what I'm talking about. It would also be helpful if you would actually contribute to the OP's problem instead of criticizing my post.

While I'll admit I'm not an electrical engineer I do know how to do a web search and I do know how an amp meter works. Your comments are merely semantics .
This web site defines both amp meters and external shunt ammeters.
http://home.cogeco.ca/~rpaisley4/Ammeter.html
There is a voltage drop (differential :edit) across the resistor on the shunt ammeter and while you may call it a volt meter I do not see it referred to as a voltmeter in any of the definitive web sites that I have researched.
Perhaps you can show me where any of the wiring to the battery gauge is connected to the negative side of the circuit. My reference to the lack of fuses in the circuit is correct and if the resistor on the shunt doesn't burn into then the small gauge wire will.

Re: Battery/amp gauge
 

i have to agree with stepside that nothing i try will make this guage work.dont think both of our guages would be bad. hookup makes no sense to me.taking a voltage reading on the same wire a few feet apart gives the same reading. my truck also has no fusable link. maybe there is enough resistance in the link to make a difference?
as far as hooking up the brown wire that used to go to #8 to #5 on the new panel, it works. the system needs a light bulb.instead of the old gen light your using the temp light in the new guage. if the bulb burns out your system wont charge, just like it would with the old panel.

Re: Battery/amp gauge
 

And there you have it. So why can you not run a resister in place of the light from the brown wire to the external voltage regulator as has been indicated?

BTW I re-read the thread and noticed you mentioned the terminal 5 on the gauge dash was for the temp light in your first post and I missed it. I should have included that in my post where I said terminal 5 dead ends. Sorry about that and hope I didn't cause confusion.

Re: Battery/amp gauge
 

72lb4x4, you last post was a bit harsh I see alot of those statements in the general forums but in the specialized sections (suspension, engine & drivetrain, electrical, ect...ect.) there seems to be a level of mutual respect and when there is a difference of opinion it's more productive to further the discussion. This thread is a perfect example.

neba, 72stepside, The system does make sense if you go back to the basic fundamental that electricity will always take the path of least resistance. The best way to explain this is to imagine a large 6" diameter water pipe with 10 gpm (equivalent to volts) of water flowing through it. If you were to tap an 1/8" line into the 6" pipe not much water is going to flow through it because the 6" pipe offers little or no resistance. Now put a valve (shunt) on the 6" pipe and close it half way you now have a pressure drop on other side of valve which is the electrical equivalent to a voltage drop and the pressure drop (voltage drop) at the end of the 1/8" hose allows water to flow through the 1/8" line the amount of water flowing is equivalent to electrical current which is expressed in amps. Increasing the water supply also increases the pressure drop and more flow thought the 1/8" line or ammeter in our case. So the current flow through the ammeter will be proportional to the current flow through the shunt. The voltage drop at either end has no direct effect on the ammeter other than influencing the direction and amount of current flow which is expressed in amps, so yes it is an ammeter (only measures a small percentage of current flow) and not a volt meter.

Vette, Thanks for verifying the paths on the circuit boards are still there from terminal 5, I don't have spare parts to double check myself also the link you posted on the ammeter is the best I've seen so far and this is a highly debated topic in this and other forums.

72stepside, Have you double checked continuity through the circuit board to the ammeter. Sorry for the long post hope it adds more help than confusion.

Re: Battery/amp gauge
 

i would like to say thanks to all who have tried to help. i wasnt trying to argue, just trying to figure it out. i agree you could add a resister, just seemed easier to plug a wire into empty socket. anyway i dont think those old guages are very accurate and will add an aftermarket set under the dash. thanks again

Re: Battery/amp gauge
 

I'm installing all new wiring harness and 1-wire alternator. My attached diagram the correct way to wire up the battery gauge? Do you have the part number for shunt? Thanks in advance.

Re: Battery/amp gauge
 

The wiring diagram you posted may or may not give the desired reading on the meter. It all depends on where you'll be drawing power for the electrical loads in your truck.

For example, if you were planning on using the "BATT" stud on the starter solenoid as your main power distribution point, your meter will only show the output current of the alternator as a "charge". It will never show "discharge" current being drawn from the battery because it's not in the path to measure that current.

Now, if you were to make the right side of the shunt your main power distribution point, the meter will show both "charge" and "discharge" current flowing to or from the battery just like the stock configuration.

The shunt that fixit-p showed back in post #5 is for ChevyII/Nova SS applications and is available from sources such as --> http://www.modernperformanceclassics...s%20Shunt.aspx

However, I see you're showing 4 gauge wiring on your diagram so I assume you're planning on using a fairly high output alternator. I don't know the exact rating on those Nova SS shunts, but I doubt that they are designed to handle much over 60 amps (the largest available alternator on a '65 ChevyII/Nova was a 62 amp unit).

As fixit-p also said in post #5, the "shunt" in these trucks is simply the inherent resistance present in the charge wire ... not a separate component. So the stock "shunt" was a section of 12 gauge wire about 4 and a half, maybe 5 feet long that ran from the junction block on the passenger side fender near the battery, across the radiator support to the factory multi-wire splice that served as the main power distribution point. The current carrying capacity of this system can be increased by using a heavier gauge wire. But that has lower resistance per foot so the sensitivity of the battery gauge will be reduced.

In other words, it would be possible to make the stock battery gauge capable of reading 100 amps or more by using a suitably heavy gauge shunt wire. But it wouldn't be very useful because you wouldn't see much needle deflection at lower currents. For example, with the stock configuration, you can see the needle move to the discharge side if you turn the headlights on without the engine running. But with a larger gauge shunt you might not see any needle movement at all.

With that in mind, I would recommend changing to a voltmeter. That will simplify the wiring and work with most any charging system. I believe member T-Bone converts the '76-'87 style voltmeters to fit '67-'72 gauge clusters.

Re: Battery/amp gauge
 

The in dash battery gauge on my 67 pickup works but only on discharge.
Can't figure it out. I know its charging because I checked with a meter 14.7v.
The truck starts every day without a problem.
Any ideas?

Re: Battery/amp gauge
 

Most likely you've lost the connection on one of the wires to the gauge. There are two wires that go to the gauge and they are both positive. I stress this because some guys think that one wire is positive and one is negative or ground.
Each wire has a small four amp fuse inline to protect the ammeter in case of a short or a high voltage surge. The first place to look is at the fuses and the easiest one to find is on the junction bolt on the right fender. The other one is usually near and below the left headlight in the harness. This is probably discussed in the thread above. Both wires run directly to the dash cluster to terminals 1 and 12 and there are copper strips to the gauge from there. It is common for these connections at the cluster to corrode and lose connectivity. so it may be a case of just cleaning the connections.

Re: Battery/amp gauge
 

Does any aftermarket supplier sell a volt meter to fit the 67 - 72 instrument panel in place of the crappy battery gauge?

Re: Battery/amp gauge
 

I wouldn't consider the factory battery gauge crappy ... when wired correctly, they actually do a good job of letting the driver know if the battery is charging or being discharged. However, as I described earlier in post #33, they will become less sensitive (and not as useful) if the shunt wire is up-sized to handle a larger current load than stock. And as I mentioned there, member T-Bone converts the '76-'87 style voltmeters to fit '67-'72 gauge clusters.


In addition to what VetteVet wrote, also check to see how your alternator output is wired into the system. For the battery gauge to function correctly, the alternator output has to be routed to the stock location, which is the multi-wire spliced junction in the harness on the driver side of the radiator support. If the alternator output is re-routed directly to the battery, the battery gauge will only show discharge even when the charging system is working okay.

Re: Battery/amp gauge
 

Yes, you are correct. The factory battery gauge worked fine in the original electrical system, but when we (and in this case, I mean me) "improve" things with larger gauge wire connected from the alternator to the battery terminal on the starter, then that factory system no longer works like it should.

Re: Battery/amp gauge
 

This thread has been inactive for a while but there is some information that I would have liked to have that I found missing. So here goes:

Yes, it is an external shunt ammeter circuit. Looking at a samle size of one, so keep that in mind. The meter itself looks to require about 800mA of current to move 1/2 scale in either direction. The response looked pretty linear, I'd expect double that for full scale deflections. I did not dare run 1.5A through that 50 year old fine wire.

Attachment 2173033
Attachment 2173034

The 12AWG red wire from the junction block to the voltage regulator connector measured 30mOhms using a 4 wire meter. I did not want to unravel to expose the splice, the regulator connection should be close enough.

Attachment 2173035

You end up with a low resistance ammeter path in parallel with a lower resistance wire path. A lot of current would need to run through that 30mOhm wire to deflect the needle. I will take a reading from the junction block to the voltage regulator connector with the red wire disconnected from the junction block to get the installed ammeter path resistance once I put it all back together. Cleaning up the instrument cluster now.


From a practical point of view, you have to make sure that ALL of the connections from the junction block, through the ammeter, through the fuses and to the splice are solid. Any added resistance in the ammeter path will cause a lower deflection than desired or expected.

Re: Battery/amp gauge
 

Very interesting. Thanks for sharing your results. I have never seen the stock ammeter needle deflect as far as it did in your test in the three 67-72 trucks I've owned that had an ammeter. I've seen it deflect maybe half that far, max, and that was after doing something like performing a compression test where I was cranking the engine over a bunch, or after forgetting to turn off the headlights while inside a store for half an hour. I've always wondered how much the needle would have deflected in a new truck that had perfect wiring.