Having issues with the charging system in my '92 W250 CTD.

I was driving home from a parts run earlier today, and noticed the volt gauge indicated it wasn't charging. Immediatly turned off the lights, heater fan and radio, and shortly afterwards noticed the trans was shifting in and out of OD.

When I got home, I checked the voltage, and it was sitting on 12.6 volts. It would start to charge, then stop, then charge, then stop, all the while the cylce of off/on charging gets faster and faster, until it seems like a relay clicking on/off fast.
Shut the truck off, switched the AC relay for the ASC relay. and nothing, not charging. Got on the Stickey, and found the instrucions for setting the Crank sensor. Cleaned up the crank pulley, and the CPS, and reset to .050. Started engine and still no charging. Switched out the Alt for a new one I had on the shelf, and still no charge.

I'm going to get a couple of new relays tommorrow and try them out, but I wanted to know if I have missed a step in my diagnosis, or do I keep plugging along? The computer is a Mopar replacement, but when it was replaced I don't know.

Any all help/info would be great. I'm going to try new relays and a new CPS, but if they don't work out then I may try the external regulator conversion.

Thanks in advance

MatthewH

 

Matthew, my 91.5(d250),is having same issue.I just got on here to see if anyone has had the same problem,( mine's auto., trans). It seems ok a idle, but more rpms, chg., needle really gets to jumping,new volt reg., I will ck.,the sticky, keep in touch.

 

I recently ran into some electrical gremlins myself I found that my connections at my battery were very poor. After cleaning everything up and putting a new connectors in making sure everything was clean bright and tight all my problems stopped just something to look at. Hth

 

I ran into that when I first put the truck back togeather. it ended up being an body ground that wasn't attached to the negitive side of the batt. That was the first thing I checked before the relays, but the batt connections and the grounds are all still tight and clean/greased.
Maybe running a ground wire right to the computer might help?

 

The OD jumping in and out makes me think crank sensor. Check the harness very closely.

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I did the regulator mod from the sticky on a friends 92 w250 and now it charges 14.75+

I didn't know the crank sensor was for the OD and not the alternator, I disconnected it when I installed the regulator thinking it would interfere. I will be installing the tps delete soon, do I still need to have it connected?

Thanks.

 

You need the crank sensor signal for OD to work. It's rare for the regulator in the PCM to die, so always make sure that it is not just a crank sensor problem before slapping a band-aid on it. Using a pot to control the OD wont work if there is no signal from the crank sensor.

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I checked the plug up top by the oil fill and it looks new and clean, but the sensor part down by the crank looks old and dirty. Like I mentioned, I sanded the rust and junk off the crank pully, and wiped off the magnetic surface and reset the gap, but I am going to get a new sensor and try it. If that dosen't work, then I'm going to do the regulator mod. Also had the alt checked today and they said it wasn't charging. Either way it still isn't charging so I'm going to have to keep pluging away.

Thanks for the responses

 

The harness is usually the problem, not the plug. Check for chafed worrying all along the harness.

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Interesting.....

I had mine flake out one foggy day. I messed with the plugs and the problem never came back. Truck has history of misplaced A21 circuit wiring getting shorted by the throttle linkage and taking out a fusible link. I'll have to take a look-see at that harness that goes along the left side of the engine.

 

Are we talking from the sensor to the plug, or the plug back to the main harness? I'll run the entire harness looking for chaffed wires and see what I come up with.

Thanks

 

Sensor circuit goes to a plug under the manifold near the rear left side of the engine, then through the main harness to the PCM. All the related grounds are wire spliced within the harness and go to the screw near the PCM. To clarify, sensor, up front of engine to round plug, down left side to square plug, through main harness to PCM.

On mine, according to the service record that came with the truck the A21 (power) wire from the IP to the KSB temp sensor was chaffed by the throttle linkage. Looks like that sort of mischief could happen to other harnesses near there.

 

Update,

I installed new relays, and it didn't help, but figured that after doing some searching, but hey, there cheap and there new.

Ran the entire harness from the CPS all the way to the computer, same from the alt. Other than some flaking factory tape by the 2 large square plugs on the back of the motor, all the wires were in great shape, no chaffing or modified wiring. I took the square plugs apart and the plug for the alt wiring harness, everything is clean and in great shape.

Still waiting for my CPS, the dealer forgot to order it on Friday when I called, so maybe it will be here tomorrow

 

Just a thought, Are all the grounds good? Stupid ground problems cause me to look stoopid......Mark

 

HaHa, Success,

Installed new CPS, shimmed to .050, and put the front of the motor back togeather. Started the truck, and once the grid heaters quit cycling, got a steady 14.30 volts. Drove it around the country block, and everything works great, shifts into OD and stays there.

Thanks for all the help and the "Sticky". If it wasn't for everybodies help, I would still be stuck, figuring out the charging system.

Thanks Again