A Ford regulator won't work. It's the wrong kind of circuit. You can use the '70s style Chrysler electronic voltage regulator but that's going to leave you with the Check Engine light on.
How did you determine the regulator is bad? That 's a very rare failure.
March, 22, 2012 AT 7:34 PM
So far I have replaced alt and bat and took alt back off took to napa had tested tested good ode says open field check light still on and doe not charge
March, 22, 2012 AT 7:37 PM
Oh I have also took the harness out of truck looked at all of wires and concters been chaseing this for a week all wires good all fuses good
March, 22, 2012 AT 7:40 PM
So I can use later style dodge 80s but I need to what wire needs to go were blue to and green
March, 22, 2012 AT 8:50 PM
There's going to be other problems but an external voltage regulator can be installed. First, since it is such an uncommon problem, lets start with some proper tests. Removing the entire wiring harness is WAY overkill in this circuit.
The engine has to be running to take these voltage measurements. Measure the voltage on all three wires on the back of the alternator. The large output wire bolted on must have full battery voltage all the time, engine on or off. One of the smaller wires must have full battery voltage when the engine is running. If either of those are missing, the voltage regulator isn't the problem. Holler back with those three readings.
March, 22, 2012 AT 9:27 PM
Did that already other techs on here said check harness
March, 22, 2012 AT 9:33 PM
Green wire 11.09 blue 11.34 batt 12.04 at bat and back of alt
March, 22, 2012 AT 10:21 PM
Dandy. Now, with the engine running, . . . woops, wait a minute. I don't have a '91 service manual handy so I'm doing this from memory. Do you have those blue and green wires plugged into the two terminals on the back of the alternator, or do they go into a little black plastic block, then there's two metal tabs bolted to the two terminals with little nuts?
If you have two separate wires, ground the green one while the engine is running, but please do not raise engine speed. If the alternator is indeed okay, which I suspect it is, doing this "full-field" test AND raising engine speed can do a lot of damage. We don't need to make more work.
What you should see with the green wire grounded is the head lights get brighter, voltage, if you're monitoring it, will go up to over 15 volts, and you'll hear the alternator sing and load the engine down. That will prove everything is good to that point.
If you have the little block that the two small wires go through, don't pierce the insulation as that will just be asking for more trouble in a few months. Instead, go here to see which terminal to ground to do the full-field test:
If you ground the wrong one, you can burn out a connection in the Engine Computer. I know from my students doing that on a "bugged" Dakota that I built. Again, this only applies if you can't tell which terminal goes to the green wire.
You can also look at this page to see if that sad drawing looks like your two smaller terminals:
That is the diagram that will be used if you still want to install the external regulator.
This next page for the newer style systems shows that plastic terminal block I'm talking about, and it explains why you can't tell which wire goes where. That's when you have to go back to that first page I sent you to.
The fact that one small wire has a slightly lower voltage than the other one surprises me because that proves some current is flowing in that circuit, it's just not enough. That green wire should be down to around 4 - 11 volts. That also means there can't be a break in the wire or connector pins, but something like that is adding too much resistance. This is where the full-field test will tell us a lot. If grounding the green wire gets the alternator working, follow it to the next connector and ground it there too. Work your way along that wire all the way to the computer and keep grounding it at every accessible test point. You're looking for the first point where grounding it doesn't make the alternator charge wide-open.
March, 23, 2012 AT 12:27 AM
What do I do with the blue and green wires does anyone know how to do this
March, 23, 2012 AT 2:24 AM
You haven't told us which setup you have, two separate terminals or that plastic block. We aren't going to guess and have you mess something up.
Did you even bother to do the full-field test? If you modify this circuit with the external regulator, what are you planning on doing about the Check Engine light that is going to be on all the time? How will you know when some other problem develops?
If you didn't look at how this circuit is wired on the web page, here's the diagram again. There's a blue and green wire at the alternator and a blue and green wire at the regulator. The regulator has to be grounded to work.