Resolved 1G Charging System Issues

[wishihadatalon]

Hi guys,

I have a 1990 GSX. On the way home from work yesterday on the highway, I noticed the SAFC in my car was displaying around 11.6 volts which I thought was a little odd. A little bit further down the road it started displaying 13.6-14.1v and then back down to 11.6. When I started the car this morning, the alternator didn't appear to be charging, again at ~11.6v. After a few minutes the car stalled and it required a jump to get going again. On the way to work, I had the same intermittent charging problem and eventually my battery died leaving me stranded. After a jump, and flogging it a little bit, the voltage read out the normal 13.6-14.1v. Driving it home resulted in the same intermittent issue. I should mention that more times than not, if I get the engine accelerating pretty quickly, the battery starts charging again.

Once I got the alternator out, I went and had it bench tested twice. Both times it tested "Good". I have another one on order, but I want to root cause this problem and never have to deal with it again. Previously I had to rebuild the entire alt/oil sensor section of the wiring harness because of field mice. I worked my way through wiring schematics the best I could to get the harness back in good order (it was mangled beyond recognition). I considered the possibility that my soldered connections were not so good, but I took and ohm measurement on the positive cable back to the battery terminal and I registered 0.2ohms. The one thing that I did notice is that there is no ground cable that attaches to the alternator case like I have seen on some other cars.

So my questions are these. Could a bad voltage regulator be intermittent and show positive results on a bench tester? Is there any other wiring that I should inspect? Does a 90 have a ground cable that attaches to the case? Could it just be a grounding issue? I'm totally lost here and any help that you can provide would be a huge help and greatly appreciated.

Thanks,

TJ

 

[ThunderChild]

i dont recall how fast they spin the testers at your average parts store, but i doubt its idle speed. sounds like a bad alt in general, but if the condition persists id start looking at your ground path from the block back to the battery and chassis.

for reference, my 92 doesnt have a case ground wire, but i added one from the case to the chassis (firewall side as mine is rear mounted). IMHO you can never have too many good grounds.

hit back once you get a new alt and do some testing

 

[wishihadatalon]

Well I finally got a remanufactured alternator installed. While it was out, I checked my wiring and that all looked good. Cleaned up the terminal ends at the battery to remove corrosion. Ultimately I think the alternator fixed it. I guess I have never seen a voltage regulator fail like that before. I'm not terribly happy with the new alternator because my idle voltage will dip all the way down to 12.5 volts at 750rpm. I figured the set point would be a bit higher there, but it's pretty rock solid at 13.9-14.1 volts at anything above idle.