Mechanics

CHARGING SYSTEM TROUBLE

1990 Dodge Dynasty • 6 cylinder FWD Automatic • 193,550 miles

I have a 1990 Dodge Dynasty Base 3.0L v6. I am getting DTC 41. Open or short detected in generator field circuit. I had a mechanic originally try to figure out why my voltage was fluctuating so much when I used my turn signals. It wasn't a big deal at the time. He tried to test voltage output at the alternator and suddenly I had about only 12 volts or less coming out of the alternator. I did have 13.6 or better. I have replaced the alternator and also now the pcm (used parts on both) no difference. I am stumped.
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Ranger812572
March 9, 2011.



Measure the voltage on the two small terminals on the back of the alternator while the engine is running. Then we'll know where to go next.

Caradiodoc
Mar 9, 2011.
I measured the voltage on those two small terminals, and there was no noticeable voltage there. Keep in mind I was using a multimeter with an analog needle (not a digital readout), but it didn't move a bit. Im getting approximately 12.3 now on at the battery with the engine running.

Tiny
Ranger812572
Mar 9, 2011.
Dandy. I always second guess myself but if you truly have no voltage there, this is going to be a quick fix. By the way, you DID have the engine running when you took the readings, right? There is supposed to be 0 volts on both terminals when the engine is not rotating, (cranking or running).

The ignition coil, injectors, oxygen sensor heaters, fuel pump relay, and alternator field are all powered from the automatic shutdown (ASD) relay. The fact the engine runs means all of those things are working, except the alternator. That only leaves the piece of wire from the splice to the alternator.

I only have a '92 service manual but the circuit should be the same. Look for a black ten-pin connector behind the battery. There will be a dark green / orange wire in one of the corners. Back-probe those terminals to see if voltage is there on both sides. The splice for all the other stuff is before that connector, so if there's a bad connection there, it will only affect the alternator.

Caradiodoc
Mar 9, 2011.
Yes, the engine was running at the time. And if what you say is the case, how do I fix it?

Tiny
Ranger812572
Mar 9, 2011.
Look for that connector and see if there is voltage on either or both sides of it.

Caradiodoc
Mar 9, 2011.
Okay, I found two ten pin connectors behind the battery. I looked for the dark green wires and tested voltage on both sides with the engine running. Both sides on all green wires had the same voltage on both sides. I also found an orange wire on the other connector, tested voltage on both sides and the same voltage on both sides.

Tiny
Ranger812572
Mar 9, 2011.
If you have 12 volts on both sides of the connector but not on either terminal on the alternator, there is a break in that wire between the two. There should be no splices to corrode in the harness. Look near the black plastic terminal block on the alternator where the wires come into it to see if someone poked a hole through the insulation to take a reading. I forbade my students from doing that because moisture will get in there and corrode the wire.

Caradiodoc
Mar 9, 2011.
When I tested voltages last night, I must have done something wrong. I followed the Dark Green and Blue/white wires from the alternator all the way back to the computer. I checked continuity on the wires all the way from the computer to the alternator (engine off). I had continuity. I started the car, and checked power all along the wires starting at the alternator. I didn't find any voltage coming thru anywhere.

Tiny
Ranger812572
Mar 9, 2011.
If by "anywhere" you mean including at the connector, there has to be a break in the dark green / orange wire before the connector. You can prove that by using a jumper wire from the battery positive post and a paper clip stuck in beside the terminal in the connector to apply battery voltage to that wire. If the head lights get brighter or you hear the engine load down slightly you'll know the alternator is working and everything after that point is okay.

Caradiodoc
Mar 9, 2011.
I ran a jumper wire from the battery to the alternator. No noticeable change in either engine load or headlight brightness. I'm just about ready to take and run a new wire from the computer to the alternator directly. No plugs or anything. On my car its just a dark green wire. There is no orange stripe.

Tiny
Ranger812572
Mar 9, 2011.
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