its been a while since i posted in here and the truck was running well after i put in the twins and fuel system etc. until this past weekend. when i first turned the motor on i didnt hear my alternator cycling on and off so i knew i needed to get my *** home! volts were down there im guessing 8-10 the whole way home(from up in the woods about 70 miles away from the smallest town) and after it sat for a couple minutes i tried to fire it up again and the battery clicked as if it was dead.
been searching/wrenching all afternoon through the threads about crank sensor, ASD relay and alternator issues. i threw an alternator at it and of course it didnt help, i replaced the relay which i thought would help the poor continuity i was getting from the relay but i still have poor continuity coming out of the blue/yellow wire that comes out of the relay.once again the alternator is not cycling on and off.
What do i need to check?all i have been using is a 12v test light. it was really dim when i tested this blue/yellow wire out of the relay(I believe the ASD)it barely lit the bulb.I know I need an ammeter right?should there be power to the crank sensor with key on power?i am also getting code 41 and 12 before and after the alternator change
ANY THOUGHTS?
thanks for reading my book. austin

 

Check ur voltage regulator. I had a simlar issue about 6 months ago

 

Votltage regulator is built into the PCM, not sure how you can check it. Does the cruise and A/C still work? Did you put a new ASD relay in or a used one? If you put in a used one I would take it off and take it apart to see if it is corroded. When my alt quit charging, I took the relay apart and cleaned it with electrical cleaner and a soft brush and Alt works again.

 

you can put in an external voltage regulator. It appears my truck had one done a long time ago, then a new altenator hooked up the stock way. I'm getting issues now too, so i think I'm goin back to the external as well. GOod luck.

Oh yeah, ext volt reg is in the sticky

 

i checked yesterday and i do have my a/c cycling on and off.would someone explain why the blue/yellow wire barely lit up my test light though into and out of the relay.im assuming the asd is the farthest one towards the front of the truck.does it seem like the low voltage out of the blue/yellow wire would be the source of my problem or just a symptom.also is there anyone that can identify that wire.i can maybe get pics. thanks

 

Here is a link to the sticky which tells you which wires you need to use. I hope the pics come out they didn't on my computer. If not look in the sticky under electrical.

https://www.dieseltruckresource.com/....html?t=128911

 

ok so being that the ASD relay sends power to the PCM then the alternator(if thats agreed) the wire that should be hot when the key is on happens to be that blue/yellow wire i think its a matter of tracing that darn wire back to a break then. i will try that but any other ideas or questions that you need to ask feel free i need to get this thing running without stopping to charge the battery every time i shut her down
ALSO: should there be power to one of the two small studs that are on the back of the alternator in a normal functioning condition? im talking about the two on the back that are together(one right above the other)
thanks

 

Mine did the exact same thing a month or so ago. It turned out to be the crank position sensor. See if you have juice to your little factory tach connector that should be taped to the steering column or at least near it.

 

well got it rolling guys thanks for the help! it was a combo of the ASD relay plug having a loose connector and the alternator harness plug having a loose connector. have power to everything and it charges.
thanks again

 

Hey, I'm new here, just wondered how to check the CPS at the tach connector. I'm guessing that if there's no signal from the CPS then there is no juice at the connector when the truck is running? Thanks. BTW i have a '93 W250 auto (unfortunately).

 

Other than connecting a tach, I can't think of a good way to check there.

If the OD, A/C, and charging system are all not functioning, that's a pretty good sign that there is no signal from the crank sensor.

 

Will that still be true if I've done the TPS-Potentiometer swap? Would there still be issues with OD?

 

Yes. If the PCM does not know the engine is running, it will not ground the OD solenoid no matter what input it sees from the TPS.

 

K, I guess I don't have the same problem since my OD works fine now after installing the POT, but my charging is still out of wack and I've never had my AC work. My charging is on and off again.