dan1066

I’d like to start by thanking Wally P, Jim Morehouse, the WSM wiring diagrams and the Rennlist search feature to help me get this far.

The car in question is a 1982 five speed

I just recovered from a no start condition caused by a bad fuel pump relay. I was checking the car electrically and when I checked the battery voltage with the car running and the alternator was not charging the battery.

Symptoms
-Battery voltage read at the battery with DMM read about 12 volts with the car running.
-The light at the bottom of the voltage scale does not light up. This may be a new condition, or I may have just noticed it when I starting troubleshooting
-The voltmeter reads zero all the time. This has been this way since I purchased the car.


Troubleshooting so far:
-Using the Nichol’s external excitor method, I proved the alternator works. After external excitation, the voltage as read at the battery with a DMM is about 14 volts.
-Excitor wire, disconnected from the alternator reads 1.94 volts with the key off and 3.53 volts with the key on.
-Next, I pulled the O connector at the CE. Voltage at O8 is 0.00V with the key off and 11.62V with the key on. With the O connector removed, voltage at the disconnected excitor wire is 2.02v with the key off and 3..43v with the key on.
-Since I was getting voltage to at O8 I reconnected the O connector and checked T1 on the 14 pin connector. T1 voltage with the key off is 0.00v and 10.64v with the key on. Just to confirm T1 on the 14 pin connector is at the back right on the connector as viewed from the front of the car facing the rear.
-With the O connector connected, I checked the voltage at the disconnected excitor wire again and it still read 1.94 volts with the key off and 3.53 volts with the key on.
-I put the whole thing back together, started the car and voltage at the battery was about 12 volts. I revved the engine to about 4K and then the battery voltage read about 14 volts.

Based on my trouble shooting so far, I think I have two problems. The first is that the bulb for the voltage scale light is burned out. The other is that I have a short or open in the blue wire that runs between the 14 pin connector and the alternator excitor post.

Thoughts?

Mrmerlin

do this first remove the wires from the rear of the alternator and inspect the blue wire it will usually shear at about 4 inches up from the alternator, just inside the orange sheathing
due to hanging the alternator from its harness.

Then with the wire fixed test the system if still no light then
remove the pod and swap out the charge bulb.

dr bob

You can test the lamp in the dash all the way to the 14-pin connector under the hood. Lift the engine side of the 14-pin connector. Find pin 1, which is the other end of the harness from CE panel O8. Ground pin 1 on the car side. With key on, the voltage light should illuminate. If it doesn't, look at the dash and pod at the bulb and the resistor. . If it does, the problem is in that front-of-engine harness between the 14-pin connector and the D+ (exciter) terminal on the alternator. Clean the 14-pin connector with a brush (I use a brass-bristled 'toothbrush') so the pins are shiny, and try the alternator again. If it still doesn't charge, you have a break in that wire most likely where MrMerlin described.


Used alternators are generally self-exciting over 3500 RPM's. There's enough residual magnetism to kick-start the exciter at higher speeds even without the bulb and resistor providing the initial excitation current. Try reving the engine past 3500 and see if the alternator suddenly starts working. You'll still want to cure the wiring problem.

dan1066

Thanks for the suggestions.
Update
Shorted pin 1 to ground and the charge light on the pod lit up with the key on. Great!
Replaced about 6 inches of blue wire going to the alternator. Shorted the new wire to ground and still no light on the pod.
So, I think my problem is that the blue wire between the 14 pin connector and the alternator is broken. Based on the condition of the wires coming out of the 14 pin connector, I think the right answer is to replace the entire harness.

dr bob

Dan--

Some historical info about the harness routing. A few years ago a local owner found that he had some erratic wiring continuity near the dipstick tube. The harness is supposed to route between the tube and the timig belt cover. If it is accidentally routed in front, engine movement will eventually wear through and break the connections. If you have this damage, it will be pretty obvious after inspecting the harness where it passes the dipstick tube. After that other owner's experience, I've been using tie wraps to secure the cable to the tube so no rubbing there. Anyway, something to look at.

FWIW, there arent that many wires and connectors in that harness. With no ABS, the list looks like the B+ from alternator to jump post, and from alternator to starter. The 50 lead to the starter solenoid. Two oil pressure sender wires. The AC clutch solenoid. And the D+ you are interested in for the alternator excitation. Off the top of my head...

dan1066

Thanks Dr Bob. I just went through the wire diagram and made a reference card of what connection goes where. My plan is to pull the harness and repair the broken bits.