Okay I have an 82 Plymouth Horizon, 1.7L VW engine.
I had to change my alternator the other day and things went down hill from there. For some reason I have a voltage drop when I slow down and take a turn. When I sit in park the car is fine right at 14.7 volts, even when I give it gas it reads fine. But as soon as I slow down and take a turn the volt gauge just goes to 12 and the car dies. I have replaced my battery, alternator, alternator belt, the belt is tighten great, my external voltage regulator, the pigtail wires to the voltage regulator and even the negative side battery cables. I have heard that the engine ground from the back of the engine to the fire wall can cause problems if its dirty. Should I replace that with 4awg wire?

 

You said when you slow down to take a turn....Maybe there is a dead short in the brake lights????If it were a wire or ground it would hppen all the time...There is a valid test and it is called the wiggle test...With the car running wiggle the wires and grounds to see if you can duplicate the problem...Bill

 

And why did the old alt fail in the first place?

 

Oh No.... The problem with those cars is the Dk.Blue Field wire Goes to all over the place !!!! Coil, ECC, Fan switch, Fan Relay,Fuse Block and so on....
Like Bill said.... Tug test and hope to find it.... Like Mr4Speed said. You might want to start with retesting the alternator....
If that don't work out.... Time to get a wiring dia. and go fishing...
Just my 2 cents.... Sorry Dude.... Keep us posted....

 

A problem such as this is almost always either a bad connection or something shorting, like an abraided harness touching, etc.

 

The old alternator failed just due to it being old im guessing. The guy who had it before me used it only for the weekends? So im guessing it sat. Ive been doing CPR (bringing it back to life) since janurary. When the old one failed i pulled into my driveway and all of a sudden the volt gauge dropped to 12 and i could hear in the tail pipe a real sluggish running. So i bought the new one and had them bench test it before leaving and it came back good. I will try the wiggle method, ill trace that negative field (drk blue) wire all through and make sure its okay as well. Thank you

 

I know you guys had said if it was a ground it would be happening all the time, and I went out and started it this morning and the first wire I wiggled was the engine ground and it suddenly went bad. So I did replace it just to be sure and the problem still happens. So I wiggled the 2 field wires coming from the alternator and also the battery cable from the alternator but it remains the same. I followed those wires to their different places especially the blue one. Could it be possible that the new voltage regulator is defective? Just trying to explore all my options

 

Yes,, most everything is made in China and of poor quality so it is vey possible...Bill

 

Yep...Could be faulty.... Also Make sure you clean the ground when you bolt back in the new reg.
I also like to run a extra wire from the reg, to the engine block for a great ground.

But keep chasing...you will find something....

 

Okay so I did a voltage drop test from the positive alternator to the positive battery, came back .30 volts which I know is way to high. So I cleaned one of the connections and tested the positive and it came back -.17 volts?? I know its measuring resistance but is a negative reading okay??

 

Under what conditions EXACTLY are you measuring this? If the engine is running, and the alternator is charging, .3V is NOT too high. If you measured this with engine off, there is something seriously wrong.

 

This reading was while the engine was running with my headlights, high beams and hazards on to load it. I watched a youtube video where the guy had said anything above .03 volts is high. But that .30 was negative volts when i took the reading

 

.3V WOULD be about the limit for a lower current circuit, say between the battery and voltage regulator and the ignition.

But .3V on the charging line is fine. Some of the tradtional Mopars ran more than that. Remember, unless it's a "one wire" alternator, the voltage sensing line is in the lower current field circuit, so if there's a bit of drop in the charging line, the regulator compensates.

I would repeat the test and wiggle the "crap" out of the harness in suspect places

This seems likely to be an intermittent short somewhere. I'm not familiar enough specifically with this late stuff to advise you

 

Clean the fuse connections

 

Okay, ill go back and do thaf. I also stepped up the ground wire and cleaned it to my knuckles to make sure, so i know the ground is good. Ill try the test again and find out, thank you.
By the way thats what were working on O.o