AZOG

Does the ground wire near the starter that comes from the wiring harness need to be attached to the starter bolt that bolts to the bellhousing? or can it be any bolt that bolts the bell housing. I am having a weird problem with my battery dropping voltage. When car is not running with all doors shut and all accessories off the battery is at 12.7. When i start the car and it is idling the battery drops down to 12.34 volts. And when I rev the engine battery stays at the 12.34 volts. Battery is new - two days old. Autozone tested alternator and they said it was good. So I have new battery and an alternator that they said is good. Anyones thoughts? ground issue? or Possible bad ECU? what else could I check for the charging system in these cars. 1987 N/A . Also already removed and cleaned wiring harness ground at the driver side strut tower.
Have not touched any other grounds. Any help is appreciated.

clokker

iTrader: (2)

Meaningless.
Battery should be over 14v when revved.

AZOG

Yeah but could a bad ground or wiring harness cause the alt to not charge properly. The alt is new too . bought acouple months ago but the car has been sitting since

clokker

iTrader: (2)

Well, anything is possible but if it's an Autozone reman, chances are that's your problem.

AZOG

It’s an acdelco reman from rockauto I believe

NCross

iTrader: (18)

Does your battery light illuminate? Pull up the FSM and check for 1V on the L terminal and minimum 13v at the top post ( comes straight from the battery). 14v give or take is ideal, but with all accessories on at idle 13v isn't too bad. Healthy battery voltage should be 12.6v at rest, anything more than that is a charge.

The only things at fault could be the alternator itself/belt/pulley, the wiring to and from the alternator, and the charge light.

The engine has 4 grounds, so unless the main ground on the bell housing is bad I would dismiss that theory.

AZOG

Thank you Ill check for 1V when I get a chance. No battery light is coming up. And what is the “charge light “ ?

mazdaverx713b

iTrader: (91)

If the ground that connects to the bellhousing is loose or has resistance you will see some funky stuff happen and you will likely melt your smaller ground that runs from the top of the bellhousing to the brass tab on the firewall. I would think your main ground would be ok. Check the belt tension and also check output voltage right at the alternator at varying rpm. It is possible that you got a bad alternator right out of the box.

NCross

iTrader: (18)

Charge light is the warning light in the middle of the dash cluster.

AZOG

Belt tension is good and I don’t believe the bellhousing ground is loose. Checked it the other day. Also my ground that’s coming off the brass tab on the firewall is connected to my UIM not my bellhousing. Is that normal ?

And hopefully wasn’t bad out of box . good thing acdelco has a limited lifetime warranty on alts . Gonna check for the 1V today and then might get a replacement just in case.

And ncross i think I understand what you’re saying . I just looked at a wiring diagram . So the L terminal goes directly to the warning “charge light “ and then after the charge light it goes to the positive battery terminal through the wiring harness . Correct me if I’m wrong . If that is bad how would I go about fixing that ? New dash cluster ? Or a repaired one I’m assuming would be better ?

Btw thank you guys for helping. Means a lot

NCross

iTrader: (18)

Usually replacing the bulb if burnt out will complete the circuit again.

AZOG

Ok so I resoldered the warning light cluster and grounded the yellow/blue wire from the CPU harness and verified all the warning lights are turning on. Plugged the CPU harness back in, Plugged the alt in and when I turn the key to ON the warning lights still dont come up. I then tried to re solder all the solder joints on the CPU. Put it back in and still no warning lights and doesnt look like alt is charging battery. Is there a way to bypass the alt warning light relay on this stupid CPU. Spent 3 hours re soldering all this and still doesnt work. Either theres a way to bypass this or im gonna have to find another CPU to buy. Any suggestions?

NCross

iTrader: (18)

If your warning lights work and you have 1v at the L terminal I suspect the alternator has failed. There are two kinds of AC Delco parts, good ones (genuine GM), and AC Delco Professional (junk). When a service writer orders ACD Professional parts or Dorman electronics I usually go inside the shop office and tell them to get something better or they're going to pay me twice to fix it.

AZOG

Im going to redo the alternator connector just to rule that out and check for 1V when i get the chance. But i just got the replacement alt from rock auto yesterday and started the car only once. Dont get how it would fail so fast even tho it is a acd professional reman. And warning lights didnt work from the get go . I think my CPU is bad because when I ground the W/B wire from the alt connector to the chassis, I get no noise from the CPU or warning lights. So im thinking the relay in the cpu is bad. I spent hours reading on this forum following tests that HAILERS posted some time ago. BUT my main question is , is there a way to bypass this stupid alt warning relay. Based off of what other people have found out in older threads it seems that if the warning charge bulb and the alt warning relay thats located in the CPU are NOT working then the ALT will NOT charge the battery. Because apparently the alt sends a signal to the alt warning relay through the L terminal W/B wire and if the CPU is bad it wont get this and the ALT wont charge. Does anyone have a way to bypass this. Spending money on another CPU just to try and resolder the joints again just seems like im gonna run into the same problem again.

AZOG

Also NCross just realized you messaged me about my RB exhaust. Sorry decided to not part out my car after all. Was trying to figure out how to remove my for sale thread.