Need advice for no charging voltage

[BAIrwin]

Hello. I have a 1997 Dodge Ram 2500 Cummins diesel 4x4 long box. I had the rectifier block replaced in my alternator at the repair shop last fall. The other day I suspected that the alternator had failed again as there was no charging voltage. I brought the alternator back to the repair shop however it tested OK. I'm wondering if the voltage regulator has failed in the PCM? I don't show any voltage (0 volts) at the two small terminals on the alternator housing. The main lug shows battery voltage. The truck starts and runs OK, just shows battery voltage. I've cleaned all the alternator connections, I've looked at the wiring harnesses for broken wires...everything looks ok. I removed all 3 plugs from the PCM, opened them up and cleaned all the connections and contacts with contact cleaner, plugged them back in. I still don't get a charging voltage. My research shows that the voltage regulator is in the PCM. Is this a common problem? Does it actually fail sometimes or is this unlikely? I'm currently at a loss... I'd appreciate anyone's thoughts to help me out. I've read that some people actually install an external voltage regulator. Are there any precautions doing this? Any helpful suggestions/links would be much appreciated. Thank you. Brian.

 

[BigPapa]

It's possible you have a PCM issue, but I'd suggest more diag. Does your A/C work or is it out, too?

 

[BAIrwin]

A/C hasn't worked for a couple of years, doesn't hold a charge. I don't turn it on.

 

[BigPapa]

OK, does your tach and OD work?

 

[BAIrwin]

OK, does your tach and OD work?

No the tach doesn't work and the manual OD button doesn't work/light up. The transmission also doesn't shift gears (same happened when the alternator failed).

 

[BigPapa]

Sounds more like an Engine Speed Sensor problem. If the ESS doesn't work, the PCM won't call for the Alternator, A/C, or OD.

 

[DavidC]

Sounds more like an Engine Speed Sensor problem. If the ESS doesn't work, the PCM won't call for the Alternator, A/C, or OD.

What he said

 

[BoeingDiesel]

Based on what BigPapa and DavidC said a quick google search came up with this.

Copied from the Cummins Forum:

The Engine Speed Sensor is used on '94-'98 12 valve diesels to tell the PCM the engine is running and at what RPM. The PCM uses this signal to control several different functions, more functions in later years. Issues with the ESS will cause problems with tach and charging. Without a signal from the ESS the alternator won't charge, the grid heaters won't work, the tach won't work and etc. due to the PCM not thinking the engine is even running. The only real way I know to test the ESS is with an oscilloscope (may not be spelled correctly). Check the wiring very, very carefully from the ESS to the PCM. Also, check the grounds all over engine and frame very well as loose grounds will cause all kinds of issues. The gap between ESS and harmonic balancer should be .049" to .050". Your suppose to use brass feeler gauge to set, but if you feel the drag carefully, the regular metal ones will work fine. If the ESS was actually touching the harmonic balancer there is a good chance it is bad.

 

[BigPapa]

The brass feeler gauge is used because the ESS is basically a magnet. Use an old gift card or credit card, they're @ 0.050".

 

[BAIrwin]

Oh OK. I've never heard of an ESS before.....I'll have to do some research to see exactly where it is. Thank you to both of you guys, it's much appreciated. It gives me another place to look. Take care

 

[BigPapa]

It's on the front of the engine between the Water Pump and the Damper.