I Have a 1988 GTA 350 TPI, The car runs with Low Voltage and sometimes Voltage is fine. New Alternator,New Battery, New Alt. PigTail.
I clean the small ground wire to the chassis and the one from the battery to the block. That seem to help and i was getting 14.7 steady. Today i turned the car on and i was getting 11.7 at the battery at idle and the same in the back of the Alt. with the car off and the ignition on the on position I check voltage at the Alt. Pigtail and im getting 12V at the red Wire, 10V at the Brown with white stripe with ignition on, and 12V at the Fuse box.What can this be? Can i run a new wire to replace the Brown/white stripe wire? I will like to get the voltage right. Thanks in advance.

 

your alternator may have a factory defect it sounds like your volt regulator in the alternator is bad

 

OH i was thinking maybe the Brown with white stripe was shorting somewhere because with the ingnition on i only get 10V at the harness and 12V at the fuse box and 12V at the battery. Does this wire have a fusebly link or does it just run to the alt harness and can be replaced with new wire? Again thanks for the help.

 

Brown/ white wire comes from the instrument cluster and shows low voltage because the "Batt" indicator is driven by that circuit. The circuits to the alternator appear to be functioning normally.

Red87GTA is correct in pointing to your alternator. You just said yourself that system voltage went lower with the engine running, and that you have power to all terminals at the alternator. Remove the alternator and have it tested.

 

I will take the Alt. to see if its good. I was just thinking that its weird that with the car and the ignition in ON position i get 12V at the 20Amp FAN FUSE but Only 10V at the Harness.If i take the fuse out i dont get no Voltage at the Harness but why im i losing 2 volts? Possible break in the Wire? Sorry for being a pain but its my First time dealing with this kinda issue.

 

if there is a break voltage is ether there or not. something is strange your whole car is basically one big unit so unless there is something like a resistor you should have 12v on every wire everywhere

 

I know i should be getting what the battery shows, Battery shows 12V, Fan Fuse Show 12V but the Brown/white wire shows 10V. Im thinking of running a new wire from the Fan Fuse to the harness and see if i get 12V. But im wondering if that wire goes somewhere else too. Thanks for all the info, i really appreciated.

 

Ok, so today i ran a new wire from the Fan Fuse to the Alt. Pigtail and got 12V before i did that i was getting 8V at the Brown/white wire. I connected the harness started the car and got 14.8 at the battery!!!
The PO was running the fans from a switch so the relays dont come to play anymore. Is this OK or will it hurt the car? I plan on rewiring all of that so it can be stock and have the relays do the work but can i run like that and not hurt anything?

 

 

Ok that sounds good! What about the wire i ran from the Fan fuse to the Alt. Harness? was getting rid of the Brown/White and running that new wire ok or will it hurt something?

 

Okay, I appologize. I don't know why I didn't catch this yesterday. The CS series alternator can be wired so that the large red wire senses system voltage to activate the alternator. It can also be wired so that the indicator circuit or a seperate exciter circuit activates the unit. In the case of your car, the brn/wht wire serves as an exciter circuit to activate the unit.

There is some sort of high resistance in the brn/wht wire on your car, or you may have a partially shorted primary winding in your fan relay that is pulling voltage low on that circuit. The brn/wht wire(circuit#250)supplies the 12v to the primary coil of the fan relay as well as to the alternator. Replacing the wire with a new one is perfectly fine. Just be sure your connections are solid. The wire does come from your fuel pump fuse. That's why it had no power with the fuse out.

As for running your cooling fan from a manual switch, not a good idea. You can forget to turn the fan on and overheat your engine. Or you can leave the switch on and burn up the fan. I suggest you repair your fan control system as soon as possible.

 

Thanks for all the help!! Yeah The PO had Low Voltage issues and never figured them out.When i got the car the fans were already wire to a switch. He claims that the Relays were bad. I discovered that the Brown/White was only getting 8V i wonder if the relay was good and there is just a short somewhere? Should i just run a new wire to the relay aswell and put new relays and see what it does? Thanks again for all the help!!!

 

I dont know off hand what the primary coil resistance should be for the fan relay, so I would recommend you replace it. Replacing circuit 250 may well solve the cooling fan issue. There are other components and wiring involved and you may have some further diagnosis and repairs to do but you found one bad circuit for sure.

Does your car have dual fans?

 

Yes it does have Dual Fans. So Running that Wire will be my starting Point.
Hopefully that will be it but im going to buy a Repair Manual to see the diagrams.
The PO had the car for Over 2 years and couldnt figured out the Low Voltage issue. I had the car 3 days and thanks to you guys i have it fixed.