My 82 GSL charging systems seems to fail once the car idles down. It started a few days ago when I was out for a ride and my voltage gauge started to act weird. The car also shut off when I go to slow down or stop. The car would start back up but would run really rough. I was able to make it home.

The next day I start the car to check the voltage output from the alternator. The voltage output was a steady 13.8 volts. Once the car got warm and idled down, the voltage started to drop. The car also start to run ruff like it want to shut off. During that time the alternator voltage output drop down under 12 volts and it was running really ruff.

I start the car again today and the same thing happen. The alernator was putting out 13.8 volts again. Once the car started to heat up and idle down the same thing happned again. Also the fuse link between the alternaor and battery is good. Has anyone else dealt with this issue? I have no idea what's going on.

 

check this thread out https://www.rx7club.com/1st-generati...estion-299390/

maybe it’s your battery that needs to be replaced

 

I've seen alternators start to fail as they heat up. Since it seems temperature related, it would be my primary suspect. If its putting out any less than 13V at idle when warm, I would be inclined to replace it.

Also, be sure to check the belt tension and check your grounds in the engine bay. While they may not be whats causing the issue, they are good to check and ensure the threads of the bolt and the captive nuts are clean to ensure a good ground.

 

I installed a new alternator and still had the same issue.

 

Replacing the alternator and having the same issue makes me think something's up with the electrical connections. I've seen grounding issues and corroded wiring connections cause weird things at different temperatures on other vehicles. I've even seen old wires broken inside the sheathing that touch when cold but pull apart when hot, but because the insulation is still together you can't see them. Really annoying to try to hunt down.

Have you got a service manual? There should be some flow charts to test the various wires and components. I found a diagnostic flowchart in my 85 manual but I don't know if it will be the same.

 

I’m going to get a new battery today.

 

As the other guys have said, a new battery might mask the symptoms of bad wiring connections for awhile, and if it starts doing the same thing in a month (*or a week), at least you'll know its not the battery or the alternator!

My point is, these cars were barely well-grounded from the factory, and with nearly 40yrs of age and corrosion in the wiring harnesses, they benefit from having new, oversized ground wires run from BATTERY negative to the various parts needing good grounds, i.e., Alternator bracket, Starter, and body at the drivers side fender. Once you do this, you'll notice far fewer issues with charging, lights dimming at low engine RPM, and even likely better fuel economy and performance.

 

I changed the battery, still getting the same problem. I checked all my connections. The spark plugs, distributor cap, ignition cap and ignition coils are all new. The spark plugs wires are about 4 months old. I’m still going to check them too because the car is running like it’s missing firing too.

The car starts without any issues. As long as the car is idled up, the output Voltage is right at 14Volts. Once it’s warms up the car runs really rough and the voltage drops down about 12.2 volts. Plus it acts like it wants to cutoff.

Am I missing something?

 

When the voltage is at 12.2V, what engine ram are you seeing? Is it that the engine rom is so low that the alternator output is much lower?

 

Changed the battery = swapped with anoher vehicle or put a NEW battery in? It matters.

Also, the idle speed should be set to about 700-800rpm. This keeps the alternator spinning at about the right RPM to generate current at idle. As long as you don't have a bunch of other electrical load on the system at idle, it should sit there all day long. What happens when it's idling and you turn on the headlights? If the engine quickly dies, it's load related. In that case, remove the alternator and have it tested (*even if it's new, it needs to operate in spec).

Keep at it, you're getting closer!

 

The RPM is bouncing back and fourth between 400-700 RPM. My car was running great until I started have this issue about 2wks ago. Going to check all my connections to make they are good. I’ve tried 3 different Alternators and still get the same results.

 

I may have missed this Fix here, but if you have not already done so REPLACE THE BATTERY CABLES. These are now (??) 4o yrs old?
Can create all sorts of charging chaos, and still "look" fine...

Stu A
80GS (yep, new cables)
AZ

 

Just curious, have you tried raising your idle to see if it stabilizes? This could be something like a fuel or vacuum issue, and the charging drop could be a symptom and not the cause of the rough idle.

 

i got rid of the rats nest a long time ago. I installed a new fuel pump and filter 2 months ago.

 

I finally had a chance to double check everything on my car today. After checking everything I started it up. It ran without any issues for a few minutes and then I notice that my primary bowl on the carburetor (RB Holley) was leaking fuel. No matter what I did it wouldn’t stop. The float wouldn’t close to stop the fuel from coming.

I removed the primary bowl from the carburetor. It was switched out with 1 from my old carburetor from RacingBeat. Started the car and ran without any issues. The fuel wasn’t leaking anymore from the carburetor. There was 13.6 volts at the alternator and at the battery. I let the car run about 30 minutes. There wasn’t no voltage different at either location. I guess my issue was with the carburetor the whole time.

The car is now running like a Champ.

 

Glad to hear the car is running well again!