Hey all,

I have been searching and searching and searching to determine the best way to tackle an electrical problem I'm having. I would like to figure this out on my own with your help (like any other problem on the FD ).

The FD drives fine (idle OK, accessories work OK, etc.) UNTIL the engine is warm, according to the OE temp gauge. After that, the dash lights dim and interior/exterior (dome lights/head lamps) flicker. The dash/gauge cluster lights dim enough to get anyone's attention, while the flickering is subtle but noticable. When I switch electircal loads (especially stepping on brakes) on after teh dimming occurs, the dimming is even more severe...

I've been charging my battery fully if I anticipate driving the car (3 times a week; 10 mile roundtrip). I'll start the car and check battery voltage; it's 14.5 or so volts. Take the car for a 15 minute spin, lights dim, etc., get back to my garage, and recheck voltage; it's 11.8 or so volts.

I had to drive about 20 miles out and then 20 miles back on one occasion, and on the way back, my idiot lights illuminated (including the "charge" indicator) and I thought the car was going to die on me. There was another occasion where I drove for about 30 minutes and the car DID die on me (after having idiot lights up of course ) Couldn't restart the car that time; my hazard lights wouldn't even work. It seems like my car was running off the battery for some time....

I took both the battery and alternator out and had them checked at Autozone. They both are in working order, according to them. I also had a "system check" done there as well when my car was warmed up; they determined that my charging system is "having issues" (I had about 11.3 volts at the battery then).

I checked pg G-8 of the FSM for troubleshooting advice on this. Voltage is right on when motor is cold. I couldn't check current (in Amps) since my multimeter is only good for 10 A (not 100 A). I have not dismantled the wiring harness yet (trying to avoid it I guess) to inspect the wiring. Battery connections and drive belts are quite tight...

So it's:

1. battery (not likely)
2. alt (perhaps)
3. wiring (who knows)

Turbojeff had an issue with a shitty alternator when the motor was warm apparently: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/3-batteries-8-months-wtf-help-332635/ (look towards the bottom). Anyone else have this problem, or any suggestions on how to solve this? SiKoPaThX had an issue with the alt wiring: https://www.rx7club.com/3rd-generation-specific-1993-2002-16/electrical-clusterf-ck-432663/

Please advise

~Mike

 

anyone?

 

If you've gone through all your grounds, I'd start suspecting the alternator is going bad. You can take it to any automotive shop (should have and electrical load tester) that can determine if it's your alternator or battery. I would think that your distance would be farther than 20 to 30 miles if done in daytime than at night when the elctrical load is the highest. Sounds to me like your running on battery power even though you charge light is only comming on near total electrical failure.

 

I have not gone through my grounds. How do you inspect them? Just eyeball the connection and see if it's solid?

Also, I have taken both my alt and my abttery to a testing station, and they confirmed that both units were working properly under load (when cold). They also ran a system test and simply said, "you have a problem". They coudn't narrow it down based on just those pieces of info...

And I should have mentioned: the distance of 20-30 miles was during the night time, when my exterior lights were on. I took the car out for a drive last weekend and put about 50 miles on it in a day. Couldn't really tell any difference during the day. When I got home and checked my battery voltage, it was about 11.6 V...

I guess one way to check if it's definitely the alt is to borrow a known good alternator and see if there's still problems. Thanks for the help anyhow.

 

put a volt meter on the battery when the car is running and see what the reading is. less than 13.5 volts is crap and the alt or it's wiring needs to be replaced or fixed. then get the battery charged and get it load tested to see if it is still healthy. the alt is not ment to charge a dead/weak battery it is to maintain charge

 

I was also a little suprised to see you didn't write the voltage while the car was running. over 16v is bad too

Check the belt too. tightness of course, but also for cracks, could be slipping. That was one of my first car repair lessons.

Then check the alt connections. I'm betting alt related.

About the grounds, steel brush or wool or sandpaper the contact surfaces, dab a very little anti-sieze compound (carries a current) on the contact sides, coat the bolt with grease or vaseline to prevent oxidation.

Battery: do you have a hygrometer? compare the specific gravity in each cell, they should all be about the same. Even if they all say bad sometimes just means needs to be charged. check the battery acid fluid levels first though.

 

I bought a used alternator from a board member and installed it yesterday. BAM! No more electical problems Man, I'm so happy about this. Flickering lights no more, battery cranks pretty strong after shutting the car down after a 1/2 hour night time drive.

So I guess the alt just didn't work when it heated up. It would have helped a lot to check current output directly from the alt (if I had a 100+ Amps ammeter handy) to narrow down the failure point. I read another thread by Kevin Landers, and appantly he had the same problem too.

Thanks to all of you for the guidance.

 

Good deal, I'm all for having a volt meter in the car, it can tell you lots of things both while the car is not running and circuicts are being used, and while it's running and different loads are being applied. Mine is pretty much maxed out when the ACand fans on high, cooling fans, rear window defroster, headlights & fog lights, radio (bose system) it seems to be right at 13.6 to 13.4 vdc. at 3k rpm running all that and it will drop below 13v at 1k rpm (Pettit underdrive pulley on just the alternator) I never see much over 14.2 volts under light electrical load. Jack

 

I seem to have a problem. I just replaced my alternator with a used one that works. The car starts runs, but after a while if i have my sound on and step on my brake my sound system goes out. I have a power fc and when I put it on battery voltage its usually around 13.7 or 13.8. This is really fustrating and I'm not sure what the problem is. Any suggestions would be appreciated.

 

first off are you running any kind of under drive pullies on your car ? ? ? Second when your applying your brakes what kind of rpm are we talking about ??? is there any way you can get a voltage reading from the power FC when your stereo is on and your applying your brakes ??? do you know the minimum voltage required for your amp to operate at. My guess is that you are at less than 1k rpm when this is happening and your battery isn't holding the voltage above 10 vdc when the alternator is not putting out enough voltage.

 

Hmmm. I'll try this today to see and come back with my results. Thanks for the help. Any other suggestions would be great.