Greetings group

Seems I'm getting an electrical issue on my 92 D250 (bear with me I just woke up).

My symptoms: flash code 12, new alternator, currently at night on the battery gauge, the volts go all over the place for a minute or two. I'm figuring its a voltage regulator issue (I work on military stuff and the regulators are built in, so I assumed that was the case in civilian jobs....silly me thinking), anyway, I've narrowed it down through this forum that it may be either a relay (I hope) or the PCM (OUCH my wallet) am I barking up the right tree?

 

The alternator charge is controlled by the PCM, the ASR relay, and your CPS. My guess is that the Crank Position Sensor is either starting to go bad, or is poorly adjusted.

Also check all the connectors from the CPS to the main harness at the firewall. I believe there are at least 3. If you have corrosion at any one of those locations you could be getting an erratic reading.

 

OK, that was something I did not think about, what does it look like and where is it located?

 

New may mean <N>ever <E>ver >W>orked.

Don't rule out the alternator, dancing brushes, or poor internal connections.

Also don't rule out the connectors on the field wiring.

 

Crazy mechanic dude.

Clean up the grounds..... Simplest fix first.

Check the gap on the CPS.. Supposed to be .050, I believe....

Check the wire connections to just about everything under the hood wouldn't hurt either....


None of these things will cost you anything but time.


Put a meter on the battery and see what actual voltage is at the battery. If you're simply going by your gauge in your dash, I wouldn't necessarily believe it until you check elsewhere first.

I looked in the sticky when I had similar issues, and found it wasn't my alt, cps, PCM or any relays. It was simply poor connections at grounds and other areas under the hood. I Simply started at one side, and worked my way around the truck clockwise until I found myself back in the same space. I also added an extra ground from the frame to the battery to the engine and back up to the alternator mount bolt. Jim Lane suggested this, and I'm sure he know what he's doing..

https://www.dieseltruckresource.com/...d-t297761.html

Cleaned all up, and issue no mo...

 

I had this issue when I first bought my truck. Initially it was a loose and corroded ground terminal connection at the battery. Didn't completely solve it but adding the additional ground loop according to the Jim Lane thread posted above solved my issue 100%.

I also recommend installing a digital volt gauge to monitor real time batt/alternator voltage. I picked one up from amazon for $5-6 IIRC. 1st gen gauges are barely better than dummy lights.