Electrical Problems
 

I am not a frequent poster on the forum, but I need some help. I teach a basic HS automotive class and a two years ago we had a 1980 trans am donated to me for the shop. We have recently did body work and engine work to the car but now are having some electrical issues.

We tried to repair some of the wiring that was spliced and taped together from the previous owners. While doing so we went from having charging volatge of 15 volts to charging volt of 12.5. The alternator is brand new. Can anyone help with what wire should be coming off the alternator for the regulator. We have a red and a black wire that plugs into the top of the alternator. We have a wire that is attached to the positive battery cable and a single wire that comes from the wiring harness. our we missing something or can we have fixed a wire and it is now in the wrong spot. We need the Help?

So your problem is you dropped from a charging voltage of 15 to 12.5?

I belive my problem is with in my wiring issues. Battery is fully charged, alternator is brand new and like i said we are not getting a charging volatge higher then 12.5 volts. When I disconect the negative cable from battery car dies. This had all started after I decided to have kids and myself correct some of the wiring issues in the car. I am not sure if I have the right wires attatched to alternator this part of the wiring harness was a nightmare with splices and wire nuts on it. We cut wires back into the harness and tried limit splices that were there. Can you tell me what wires from the harness should go to the nut on alternator and what plugs into alternator?

Don

If you sign up on Autozone.com they have schematics and repair info

or if this link works try this.
http://www.autozone.com:80/autozone/...00c15280080df1

the nut on the alternator should have a heavy gauge positive lead from the battery.

for the old alternator to be charging at 15 volts and the new one to be 12.5, i would feel that your new alternator is bad or that you are experiencing belt slippage.

here is what i could find, hope it helps. let me know if the pics don't appear:
btw this was for an 82 firebird, as far back as i could go

figure 1
http://www.alldatapro.com/alldata/PR...07104/41918616

figure 2
http://www.alldatapro.com/alldata/PR...07104/41918617

To perform regulator tests, the following measuring instruments will be needed: resistor (10 ohms, 3 watts) R1, variable resistor (0---300 ohms, 3 watts) RV, battery (12 volts, 2 pieces). BAT1, BAT2, DC voltmeter (0---30 volts).

1. Connect instruments as shown in Fig. 1.
2. Measure voltage at BAT1 (V1). Voltmeter reading should be 10---13 volts.
3. Measure voltage between terminals F and E (V2). Voltmeter reading should be approximately 2 volts.
4. Measure voltage between BAT1 and BAT2 (V3) with terminal S disconnected. Voltmeter reading should be 20---26 volts.
5. Measure voltage between terminals E and F while varying resistance gradually with variable resistor. Voltage should increase from 2 volts to 10---13 volts without any interruption. If voltage increase is interrupted, replace regulator.
6. Measure voltage between intermediate tap on variable resistor and terminal E (V4) without actuating variable resistor. Voltmeter should read 14.0---14.6 volts, or regulator must be replaced.
7. Connect instruments as shown in Fig. 2.
8. Measure voltage between terminals B and E while gradually increasing voltage with variable resistor. Voltage should increase from approximately 2 volts to 10---13 volts. If voltage does not vary, replace regulator.
9. Check voltage between intermediate tap of variable resistor and terminal E without actuating variable resistor. Voltmeter should read 14.5---16.6 volts, or regulator must be replaced.

http://www.alldatapro.com/alldata/PR...93587/83195243

It sounds like you have battery voltage at the alt. the brown wire goes to the idiot light. If it is not connected correctly the alt will not 'turn on'. I'd start with that.

I have to go home and look up the two red but iirc the big wire to the BAT term goes to 'the splice'. The smaller red is load sensing and I'm forgetting exactly where that should go.

No vat40 in the shop?

Still Plugging way
 

Thanks to the guys who have been helping me out with this problem. Still working it out, am going to try another alternator, but am pondering getting a new wiring harness for the car. Weather getting nice and car is road ready would love to get it out and hopefully meet some of the people who have helped out. Brown wire was never touched red wire from the plug into the alt. goes to a connector on the passenger side of the engine compartment Red wire with white connector. Never touched the wire from the battery to the alt. The probelm i feel is the splice we have no splice or fusable link. does anyone know what wires should go to splice and the where the fusable link should be attached to?

Thanks For the Time

Problem solved
 

Well feel like idiot attached the wire for the high spped fan to the alt. instead of the power wire that needed to go to it. Thanks for everyone that helped out. We are now taking on the task of wet sanding car.

Don

good to hear you finally got it

Yes, IIRC that wire also comes off "the splice".

Nice to hear it's fixed. Now post pics!

Just in case you re-examine the harnesses in that car, if you need new wires, call American Autowire in Bellmawr, NJ. Ask for Mike, he owns it, maybe a school discount (can't hurt to ask). His stuff is top shelf.