thegreatmrp

I am having ongoing charging problems with my mustang. I recently upgraded from the 75amp to the 3g alternator and the problem persists. The car is an 88gt convertible 5spd.

When driving if i don't start any accessories the gauge will show the battery charging. As soon as I turn on headlights it will dip but still charge. All seems OK. As I am driving though i notice that its not charging periodically and then the voltage gauge goes lower and lower. Sometimes it will spring back up and start to charge. For a while I thought it was just a bad gauge. It also seems to charge better at lower rpms, but most of my driving is on the highway at 3k rpms. I have changed the belt several times as I thought it might be slipping. While driving last night with the headlight, heat and wipers on I got the battery indicator light to come on for a moment.

The old alternator was doing the same thing then eventually stopped charging. I don't know where else to check. Could it be a computer problem or is there a wire I should be checking? Maybe the computer?

Done so far: New belts, at least 3 before alt swap and on second one with new alternator. I checked for continuity and voltage when I installed the new alternator. The battery has new terminals and new wires going to the block and starter solenoid all 4ga. When I did the swap I also upgraded to 4ga from the alternator. The grounds appear to be ok, and clean.


Thank you for any thoughts or suggestions.

shonerized

are you underdriven? re: underdrive pully's ?

thegreatmrp

No, its not under driven and the 3g alternator has the correct original size pulley. Its very annoying. It has me stumped.

mjr46

could have a bad alt, reman stuff if that's what it is are prone to failure quicker then a new one

thegreatmrp

mjr46, It's a new alternator not a reman, as the reman never worked at all when I first tried to install it. That being said its a Duralast Gold (which they assured me is new but who knows), so its not top of the line but they had it in stock when I needed it (love last minute repairs). And I had it tested before I left the store and once since.

It really seems like its a bad connection somewhere, like it decides to charge or not charge at random. I notice that when I hit a bump sometimes it might start to charge. I've been trying to watch it like a hawk. I've looked at the schematics but im no expert, but im thinking something in the dash controls charging? I've looked at everything under the hood. I've checked continuity across all the wires to the alternator. Does anyone have a better understanding of what tells the alternator to charge?

Thanks everyone