Dimming lights, altenator or battery?
 

I have a 71 c10 with a 350, i noticed when i bought it that the lights would get brighter when i accelerated. I replaced the altenator (70 amp) but still does it. I started using a 760 watt Schumacher power converter and i have it running thru the lighter to plug in some 110's. I installed a stereo system, 250 watt Kenwood with 500 watt speakers, nothing fancy. I took my home theater subwoofer which has a 110 plug in. After a couple of minutes of sitting idoling the coverter statts beeping saying low battery. I installed a 100 amp altenator last week and the lights are still dim til i accelerate and the converter goes about 5 to 10 minutes before it indicates low battery. I also have a battery kill switch. With all that said, it my battery? Battery is 700 cold cranking with 95 reserved capacity. Anyone have advice?

Re: Dimming lights, altenator or battery?
 

100 amp alternator pulling these kind of watts=
250 watts = 20.833333333amps
760 converter=63.333333333

I'd say your maxing out the alternator & battery pretty quickly.

Charge the battery up good and crank the truck up Have some one turn everything on and take a voltmeter and check the voltage of the battery with all of it running. Do this at idle and have them rev the motor and see what voltage you get anything less than 12.5 is not going to work.:chevy:

Re: Dimming lights, altenator or battery?
 

If it still has the old style external regulated alt, replace with a newer 12SI style internal regulated. Several threads on subject. The 12SI has about 7 amps more output at idle speeds. Should fix the dimming lights at idle issue.

Consider getting a second battery and a splitter. Run the portable earthquake rig off the second battery.

A lot of those 12 to 120 converters have a pretty high cut off to prevent winding up with a dead battery.

Re: Dimming lights, altenator or battery?
 

I will test it like you described and see what happens with the voltage on the battery but at this point do you think a larger battery wouldn't help

Re: Dimming lights, altenator or battery?
 

I took all the steps that you said and the battery still was at 12 1/2. The lights were still dim until we gave it gasand that includes the dashboard

Re: Dimming lights, altenator or battery?
 

install the internal regulated alternator,I hear they work alot better

Re: Dimming lights, altenator or battery?
 

I have a new CS144 alternator in my truck, which is what they put in 1993 C1500 Cheyenne trucks, Optional Heavy Duty 124 Amp. It is a more modern model than 12SI alternator. I have no radio and only significant draw are from plain stock headlights, the A/C blower motor, and the GM HEI distributor. I have not added a relay to the headlight wiring, it is a plain stock setup. The headlights are noticeably dimmer at idle, such as when I stop at a stop light or stop sign. The same thing was true when I had a 12SI in it, and the only reason I replace the 12SI is because the bearings were wearing out. I believe this lower output voltage of the alternator and dimmer headlights at the lowest RPM of the engine is normal. I would not try to fix it unless the problem was severe.

Re: Dimming lights, altenator or battery?
 

No it's not normal! It's a condition of the system in these trucks. The head light relay addition is a great way to get better working lights. It takes all the load off the whole wiring system. In turn it makes the components last longer like head light switches ignition switches dimmer and any other component.

The problem is you are way over loading the system.
Even if you buy the biggest battery you can it want help. Yes it will play longer at Idle before it quits but it will do the same thing because at 12.5 volts your using more than you are making.
If you are still using the original regulator system then I suggest the upgrade before doing anything else.

To fix it if it where me:
Buy at least 140 alternator with internal regulator Min and install 2 batteries.
Hook them up in parallel which will be 12 volts but double your amp hrs which in turn will run longer.:chevy:

Re: Dimming lights, altenator or battery?
 

Let me understand this correctly. On a stock 67-72 GM truck with no accessories, without a dual battery, with stock headlight wiring, do you think it is not normal/expected/typical, for the headlights to be dimmer at idle than at higher RPM?
Or are you just suggesting some enhancements that could be made to the stock configuration that would reduce that effect?

Re: Dimming lights, altenator or battery?
 

I wonder if it would be worth it to swap the pulley on the alternator so it is spinning faster at idle and charging more. You would want a smaller pulley on the alternator.

I would say dimming at idle is not abnormal, especially if you still have a generator.

Re: Dimming lights, altenator or battery?
 

You need to upgrade your wiring to support a flood of amperage that its trying to pull. Your charging system sounds choked and cant support everything-its like trying to drink a shake using a coffee stir stick. You need upgraded wiring to support that alternator-and fwiw imo SI alternators suck-go with a CS.

Re: Dimming lights, altenator or battery?
 

If the lights go dim on a stock truck with no mods it's the external regulator and the wiring.
The stock system has a built in excitement wire that tells the alternator when it needs to produce more voltage depending on the draw but it has to be above a certain RPM for it to kick on. At idle it kicks off and that's why the truck, & dash lights dim. Plus the fact of how it's wired.

Here is a link to some very good reading on how the GM system works and why to's. They explain it much better than I. I did mine off this page as well.

http://www.madelectrical.com/


With a internal alternator this problem is helped but not always fixed due to the wiring. Some of the earlier internal alternators needed the exciter wire also but later models didn't. The dimming is also caused by slipping belts and worn out belts as well.

Wiring is also a problem depending on how well it was maintained over the years. Take a volt meter and hook it up inside the truck on a hot wire and ground it. Crank the truck up and see what kind of voltage you get at idle with everything off. Then start turning things on and see how it does. This is a quick and easy way to see how the system handles the loads. It should stay around 14 volts with a good wiring system.:chevy:

Re: Dimming lights, altenator or battery?
 

Whoa, I am I missing something here.

Andy you say that a 760 watt converter draws up to 63 amps? And he is running it through the stock cig lighter? I think stock wiring for the lighter is 12guage 20amp maybe even smaller.

If that is the case you need to upgrade your wiring. The main power wire that goes to the cab is only 12 gauge and that has to power all accessories. I think you are asking for trouble by running it through the lighter. Try hooking the convertor direct to the battery and see if you dim lights go away.

Re: Dimming lights, altenator or battery?
 

It's been a little cold and damp and a little bit of rain here in Seattle Washington but I'm going to go directly to the battery and see if that makes a difference which I know it would and I'm going to use a thicker gauge I'm thinking of using an old jumper cable any thoughts?

Re: Dimming lights, altenator or battery?
 

Like has been said change to a CS series alternator and upgrade your wiring. For the smaller CS130 which is still over 100 amps an 89 Pontiac Safari is a suitable listing. They charge much better at idle than the si series. I've never used a CS144 so don't know if you would have any mounting modifications to do.

Re: Dimming lights, altenator or battery?
 

The CS144 is about one inch taller than the stock or 12SI or CS130. So the top bracket comes close to the radiator hose. I imagine in some installations the bracket could rub the radiator hose, which would be a problem. The CS144 I bought has a metric bolt hole for the top bracket bolt, and the bolt that it requires was thick enough for me to need to file the inside of the bracket to be slightly wider. Given these facts, I probably wouldn't repeat using a CS144 on another truck, unless I had a significant reason for doing that. I was overly-enthusiastic when selecting which alternator to use. :-)

Re: Dimming lights, altenator or battery?
 

I had to file the bracket for the 12SI I used. Top bolt was 10mm.

Re: Dimming lights, altenator or battery?
 

Being overly enthusiastic when selecting a CS144 reminds me of about 45 years ago when putting in a 200 amp service into my first house which was only 1000 sq. ft.

Re: Dimming lights, altenator or battery?
 

[quote=vince1;8455404]Being overly enthusiastic when selecting a CS144 reminds me of about 45 years ago when putting in a 200 amp service into my first house which was only 1000 sq. ft.


Or maybe this



https://youtu.be/Xe8DKfoscQA