So my check engine light comes on from time to time. When i cut the truck off and turn it back on it goes off. How to diagnose the problem?

 

Turn the key on
Turn the key off
Turn the key on
Turn the key off
Turn the key on

Then count the flashing CEL. There'll be groups of 2, for instance, 1 flash, pause, 2 flashs, pause
That would be a code 12

Come back with the info.

 

BTW, a bad voltage regulator will cause those symptoms, without throwing a code...if you dont get a code following the above instructions, have the alt checked..

 

Mine did it and my ground to the core support had fallen off.

 

Will do. Also my temp guage is bouncing.???

 

Mine was doing that and turned out to be the Voltage regulator was going south.

 

anyone got a picture of where the voltage regulator is located?

 

On a 92 the reg is in the computer behind the battery.

 

That may be possible, however on both my 91 and my current 93, the voltage regulator is in the Alt itself, requires replacing the alternator itself to resolve the issue.

 

What? I am not aware of any 89-93 Dodge diesel equipped trucks with a OEM internally regulated alternator unless its an aftermarket piece. As Dodgenstein said, the PCM should control the charging system on a 92.

 

First gen, the only electronics in the alternator itself is the diodes. Regulation is external. Stock, the regulator is in the PCM, but can be replaced with a separate voltage regulator for repair.

 

There's a possibility of 1 of 2 things is causing this:

1. Some engines with age will cycle the thermostat at an erratic rate, this can cause temperature spikes that the gauge will register.
This CAN be a sign of a faulty thermostat, they don't last forever.

2. A grounding issue in or near the gauge panel. Under the dash, just to the right of the column, there is a gold colored plate with several wires attached to it. This is the dash harness ground plate. Look for several wires attached to the plate and tighten them down.
Also, behind the cowl covers (AKA; Kick Panels) are the dash frame support screws, loosen and re-tighten them for good measure.

I can't stress enough how big of a joke the factory grounding on these trucks are, so I am always telling people to check any and every ground, especially when there is an issue that causes erratic component, gauge function, or lighting issues.

Also, the best thing you can do is run a heavy ground from the battery cable to the core support, to beef up the weak one already found there.

Mark.

 

Ok thanks. Where do i get a PCM if its the problem? Dodge?

 

Test it first, these things are pricey. If it fails, some one on this board may hook you up, then ebay, then aftermarket. I doubt Dodge has new ones left , but may have some in their remanufactured catalog.

 

Easy guys, I said I wasnt positive! My truck was having similar issues, which finally led to a no-start, no charge situation, when having the alt tested, I was told by the guy at NAPA that the reg was internal to the alt, but apparently he was wrong? Now I have learned something new, again.. thanks!