Electrical guys.... please help?

[66 Tiger]

I noticed the other day that my voltage fluctuating. Being that I have the stock guages I decided to verify their acuracy & wired my digital multi meter to a lighter adapter & noticed that it was indeed dropping from 13.9 down to around 12.5 volts. The odd thing was that it seemed to only do this under acceleration or when I hit a bump? I have a 135 amp alterstart alt & a new battery. Both are about 3 mos old. Does anyone have any experience with this? Thanks... Oh yeah, this is on the 1990.

 

[gabourie]

Have you upgraded the factory wiring, the ground cable, the power wire from alt to battery, from battery to solenoid

increase these to 4 gauge or better, even though you have upgraded to the ho alt, you are still bottle necking the charging system throught the crappy factory wire

I upgraded all of mine to 0 gauge, but I have my battery in the trunk and a good stereo

 

[66 Tiger]

I used the two 12ga factory wires plus installed an 8ga wire and ran it straight from the battery to the new alternator. I haven't messed with the solenoid wireing because the car is starting fine.(for the now!) What should I change the ground wire out to?

 

[Michael Yount]

The bigger the better. And I'd go through and loosen, clean and retighten every ground I could find. Perhaps you've got a loose ground that's moving a bit and not making good contact under acceleration/deceleration.

 

[jrichker]

3G alternators need a 4 gauge ground wire from the block to the chassis ground point where the battery chassis ground is located.

 

[Black Sun 5.0]

I had the same issue, bad ground. 2 and a half years of mechanics looking for the issue, it was the ground that went from the battery to the inner fender wall. Burned a hole right though.