Battery Gauge Question

[6772owner]

I have searched around on the forum, but couldnt find the specific answer I am looking for. I am trying to make the factory "battery" charging gauge functional. I have eliminated the voltage regulator and ran a wire from the alternator to the gauge, but before I hooked that wire up to the gauge I checked the cluster and their is constant power to both terminals right now. Where do I start with this thing? I am assuming that there should be switched power to one side and the wire from the alternator on the other side? Any suggestions?

Thanks

[neonlarry]

The gauge in our trucks is an ampmeter not a voltmeter. Also our particular ampmeter is a bridged circuit and yes there should be power to both sides. If you want a voltmeter I would suggest you go to your local JY and rob an 73-87 cluster of its voltmeter and install that in your cluster.

[6772owner]

Ok so there should be constant power on both sides? or just one side? I swear I read another thread that said one side should be switched and the other to the terminal on the alternator? I just want teh factory gauge to function as it should, thats all. Thanks for the help. Oh and its a 67' K10 if that matters.

[mhicks]

The amp meter I think is setup to measure the voltage drop across a resistor. So actually what it is doing is measuring the voltage on one side of the resistor and using the other side for the meter's ground even though it is not at ground potential.

[6772owner]

WOW ok well i have no idea how to make that happen lol Any one have a wiring diagram for this? I ordered a diagram, but its no help

[neonlarry]

Do you have factory wiring to the ampmeter and its not working? If so replace the 4amp fuses in the little black rubber fuse cases on both inner fenders.

[VOLZ1207]

Im new to site and just purchased a 72 lb cheyenne super 10. I have replaced battery, alternator, regulator and both 4a fuses. The battery keeps running down. The ammeter reads just above half while running. I can also remove negative battery cable while engine is running and it will continue to run. I do not know what the problem could be. I have tested the 4a fuse line with test light. Any ideas would be quite helpful. Thanks

[6772owner]

Ok thank you very much, I will check those, I believe that I have all the factory harness intact, I purchased the vehicle as is and have been trying to figure out little quirks, such as this ever since. The gauge cluster does has the battery gauge option on the flexible circuit board. Again thanks for the help.

[VetteVet]

Originally Posted by 6772owner

I have searched around on the forum, but couldnt find the specific answer I am looking for. I am trying to make the factory "battery" charging gauge functional. I have eliminated the voltage regulator and ran a wire from the alternator to the gauge, but before I hooked that wire up to the gauge I checked the cluster and their is constant power to both terminals right now. Where do I start with this thing? I am assuming that there should be switched power to one side and the wire from the alternator on the other side? Any suggestions?

Thanks

We need to clarify some things. Is your truck original or has someone hacked up the harness and re-wired a bunch of things?

Neonlarry's post no.5 explains how the ammeter should be wired and why the meter may not work.
In essence the ammeter is wired with one wire on the positive side going to the battery as shown in the diagram at the top center and connected at the junction block and the other side is connected to the alternator but not directly. IOW it is hooked to a positive source that the alternator is also connected to. It is shown at the bottom just above the horn and it connects to the three red wires. If you have wired the alternator and the battery directly to the ammeter then there's a good chance that the external shunt on the ammeter is burnt out and it will not read. See bolded red in your quote. That is what the 4 amp fuses are supposed to protect. They should be located in the front harness that runs just behind the radiator support and just over each headlight.
Below is the diagram Larry refers to. HTH

[VetteVet]

Originally Posted by VOLZ1207

Im new to site and just purchased a 72 lb cheyenne super 10. I have replaced battery, alternator, regulator and both 4a fuses. The battery keeps running down. The ammeter reads just above half while running. I can also remove negative battery cable while engine is running and it will continue to run. I do not know what the problem could be. I have tested the 4a fuse line with test light. Any ideas would be quite helpful. Thanks

Actually you have just hi-jacked this thread. Most of the folks have already looked at it and will not see your post. You should start a new thread and you will get more responses. Your problem is different than this and may have a much different solution. Just copy/paste and insert in tne new thread. Thanks.

[Jeffvega]

do all ammeters work this way? mine is stock and not working and I was going to replace it with a aftermarket style to match the rest I've changed.

[Lugnut64052]

I had more-or-less the same question a few months ago while I was doing extensive harness modifications (upgrading to an internally regulated alternator). In my case, the fuse by the battery had been cut out of the harness. I didn't quite understand what that circuit was doing until VetteVet set me straight.

You should be seeing power on both wires and the gauge is an ammeter. The ammeter circuit starts at the red wire junction downstream of the alternator, through the first fuse, then to the gauge, back out of the gauge, through the second fuse by the battery, then ends at the junction block by the battery. It parallels the main red wire from the alternator to the battery, thus letting it measure system load. VetteVet included a helpful copy/paste in another thread that helped me see what that circuit was doing.

[Jeffvega]

maybe my gauge is working then since mine also is disconected at the bat. side. the gauge always reads discharging, but I know its charging. would power to only the junction side make it always read this way?

[VetteVet]

Originally Posted by Jeffvega

maybe my gauge is working then since mine also is disconected at the bat. side. the gauge always reads discharging, but I know its charging. would power to only the junction side make it always read this way?

I would say so because you would not be reading a differential between the battery and the alternator rather you would only be connected to the alternator side. A long enough piece of wire to reach from the ammeter + to the junction on the passenger fender well with a small fuse inline should make it work. As you have seen in the thread a 4 amp fuse is the size you need.

[6772owner]

Ok well I should clarify, I did not actually hook up anything to the gauge yet, I started to then stopped when I looked at teh back and saw that I had the factory connections already. I was expecting to find nothing like my 72'. Also I believe that the harness is still in factory condition and has not been modify, save mor the external regulator deleted (that was me though) I did look and the fuse on the drivers side is missing, so I will try that first, then go from there. I appreciate all the help and guidance greatly.

[6772owner]

Alright last night I put a fuse in the drivers side fuseholder and the gauge seems to work, I say "seems" because it doesnt move very much towards charge and I havent seen it move past dead center (towards discharge) sound normal? I have never seen one actually functional in person.

[neonlarry]

Sounds normal to me, it should show some discharge when you are cranking the starter though. If it shows discharge that means your alt is not keeping up with what your accessories are using. Thats when you get a dead battery.

[6772owner]

Ok thank you very much, I hope the 65 amp alternator can keep up with the factory demands LOL Good info to know though

[fixit-p]

I just installed a 12 si alt. in my 69 and did some reserch on the ammeter. The red wire going from the batt to the alt junction is the ammeter shunt that is it is a fixed length and fixed gauge so therfore it has a fixed resistance and is calibrated with the ammeter. The external shunt type ammeter measures the voltage drop from one end of the shunt and the other (power on both sides) if the voltage on the alt side of the shunt is higher than the batt side the ammeter shows charge if the voltage at the batt is higher than the alt side it shows a discharge. If your ammeter is reading a slight charge after startup then drops to the center its working if it shows charge all the time than you would be over charging your batt. One mistake I made when I installed relays for my headlights was that I installed 8awg wire from the alt to the batt in doing so I changed the resistance of my shunt and my ammeter was off. someone mentioned the voltmeter from a 73-87 if it fits that would be a great upgrade.

[neonlarry]

73-87 voltmeter will fit in place of the ampmeter with very little effort (a little trimmimg of the tabs on the gauge face and cuttingthe mounting post off the back). You can still use the factory wires buy running the wire that comes off the negative side of the gauge to ground.

[Lugnut64052]

Originally Posted by fixit-p

I just installed a 12 si alt. in my 69 and did some reserch on the ammeter. The red wire going from the batt to the alt junction is the ammeter shunt that is it is a fixed length and fixed gauge so therfore it has a fixed resistance and is calibrated with the ammeter. The external shunt type ammeter measures the voltage drop from one end of the shunt and the other (power on both sides) if the voltage on the alt side of the shunt is higher than the batt side the ammeter shows charge if the voltage at the batt is higher than the alt side it shows a discharge. If your ammeter is reading a slight charge after startup then drops to the center its working if it shows charge all the time than you would be over charging your batt. One mistake I made when I installed relays for my headlights was that I installed 8awg wire from the alt to the batt in doing so I changed the resistance of my shunt and my ammeter was off. someone mentioned the voltmeter from a 73-87 if it fits that would be a great upgrade.

Interesting!
I did the same thing when I upgraded to a CS alternator-- used 8 gauge from the alternator to the battery. That may be what woke my ammeter up. Upon startup, it lays over to the right quite a ways, then gradually settles back down, sitting just to the right of center. It's working; I just never saw one that worked quite that good. I don't remember ever seeing one that was quite a lively as mine is now, and figured it was the more powerful alternator charging heavily for a few minutes right after start up.

I'm curious to know how your ammeter behaves with the heavier wire.

And I agree; a voltmeter is an upgrade in my opinion. Here's a thread by gringoloco that's primarily about a Camaro tach installation, but he also does a slick voltmeter upgrade in the process that looks exactly stock when he's done.

[fixit-p]

My ammeter seems like it's not as sensitve as it was, after startup it still moves to the right then drops back to center just not as much movement as before. Thanks for that link with the tach and voltmeter it looks really good I like that it looks like the stock ammeter but is voltmeter which gives you more info on your elect. system

[Ricks 71]

fairly new to the site. thanks for you input. this fixed my gauge. was not aware of the 2 fuses, it was driving me nuts. again thank you.