[wantono]

1991 dodge ram diesel, new alternator, voltage regulator, power going from ignition switch
To voltage regulator and from regulator to alternator when key is in run did no fuse-able link Alternator sill does
Not charge. What should I check for now?

[TxGreaseMonkey]

. Test all under hood and under dash fuses with a test light or multimeter:

https://www.askmehelpdesk.com/cars-t...tml#post252145

. Check wiring, connections, and grounds.

. Check the PCM, if the problem persists.

[wantono]

Thank you TxGreaseMonkey
Have checked all wires connections and grounds seem to be everything okay voltage regulators is mounted on firewall not sure what PCM is or it applies to this model. Still does not charge I have power going to and from voltage regulators
Alternator has no magnetic pull when engine is running.Do you have any suggestion.Thank you for reply

[TxGreaseMonkey]

PCM = Powertrain Control Module (computer). PCMs work with the alternator in charging the battery. Therefore, you may need to have the computer checked. No magnetic pull sounds like a PCM-alternator problem.

[TxGreaseMonkey]

Background Information on PCM-Alternator Interface:

Check Alternator FR Signal. Have alternator inspected, if idle speed fluctuates with electrical load. The FR signal communicates to the PCM how "hard" the alternator is working to meet the electrical demands of the truck, including the battery and any loads which aren't monitored by the ELD. This square-wave signal varies in pulse width, according to the load on the alternator. The PCM places, approximately, 5 reference volts on the wire. The voltage regulator will drop this signal to approximately 1.2 volts, in proportion to alternator load. The PCM compares the electrical load (ELD) signal with the FR (Charging Rate) signal from the alternator and uses that information to set the idle speed and turn the alternator on and off. This helps fuel economy.

[TxGreaseMonkey]

Be sure to check the megafure, using a multimeter, between the alternator and the battery. Often, it's located on the end of the under hood fuse box.

[wantono]

Thank you Very much TxGreaseMonkey
I Google megafure and found no definition,I check all wires using a multimeter to omen the wires is there anyway to by pass the pcm and make the alternator function. I know on a GM. You can by pass the computer by hooking up a 12v supply wire from ignition switch to alternator.
I currently do not have the option of having the computer checked. Thank you

[TxGreaseMonkey]

A megafuse is often a 175-ampere fuse between the alternator and the battery. It's the biggest fuse in the vehicle. There's no way, I know of, to by-pass the computer and have the alternator work. I don't think it's possible.

The megafuse is easily overlooked. It may be on the end of the fuse box with a cover over it. It's usually located between the two main terminals going into the under hood fuse box. I always remove both of those cables, clean the contacts, and apply dielectric grease.

[wantono]

91 dose not use pmc 92 dose, if disconnect the blue wire going from ing to the voltage regulator and leave the green wire from the voltage regulator to the alternator on, the alternator will charge wide open but if I leave it hooked properly system will not charge any ideas thanks

[wantono]

Problem Solved after trying every thing rewiring whole system no luck .Then out of frustration I tried grounding out the filed from the voltage regulator to the alternator and every thing starts working . So I went and bought a third new voltage regulator. And every thing is working grate.Thank to TxGreaseMonkey for all the help.

[wantono]

Problem Solved after trying every thing rewiring whole system no luck .Then out of frustration I tried grounding out the filed from the voltage regulator to the alternator and every thing starts working . So I went and bought a third new voltage regulator. And every thing is working grate.Thank to TxGreaseMonkey for all the help.