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Well heres the deal.. my trucks a 93 cummins with a 5 speed.. the other day the check engine light came on but every thing on the dash was reading normal.. after i shut it off and started back up i noticed it wasnt charging.. so i got it home pulled up the codes 12 and 41.. which doesnt really tell me a whole lot.. i got my voltmeter out and started doing tests and found that my feild wires on the back of my alt are not getting any voltage atall with the key on... what could cause this?... thanks, Trev.
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orginaly posted by philip on another thread
"12 is nothing. It isn't listed in the FSM.

11 no reference signal from during cranking. Crank position sensor.

24 TPS voltage high or low.

41 generator field not switching properly.

55 isn't in the manual.

Ok check the crank position sensor first. The gap should be .050". Check the voltage to the crank sensor. It should be 8 volts."

I know that you didnt need all those code but its what i could get. like stated above check the air gap in the CPS. Idk if you know where its at. so here goes its at the top of the harmonic balncer if its too far it cant read engin rpm so it wont let the alt work
hope this helps {I also hope I didnt offend you philip by quoting you off another thread}
ch
 

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Discussion Starter · #3 ·
yea ive read through all that.. but shouldnt one of the feild wires have voltage with just the key on ( truck not running ) ? or is it only energized when the CPS tells the computer the engine is running...

originally posted by Steve g in another thread

"First off, it's a very simple procedure to isolate the charging system failure. You need a voltmeter that you can attach to the battery and/or alternater so that you can see it while working at the alternater. There are 2 small wires and one big wire on your alternater. The large one whould have battery voltage at all times. Hook your volt meter pos lead here and ground the other. You should have battery voltage. Now turn the key on and using your volt meter or a 12 v test light check the two small wires at the alternater. One should be live, reading battery voltage. Note which one this is. Start the truck."
 

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If the PCM doesn't see a RPM reading it will not turn on the auto shutdown relay. The ASD relay controlls the power to the alt and A/C compressor.

Your not showing a code 11. I would still check the air gap on the crank sensor. Its .050".
 

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Discussion Starter · #6 ·
ok so there is voltage to one of the field wires, ( 10.5 V for maybe a second then shuts off ) its difficult checking this by your self haha .. checked the gap for the CPS and its less than .050" is it a problem if its too close ? or is it only when its more than .050 there is also voltage to two of the wires that go to it when the key is on.. one has 8.5V and one around 4 ish ... im stumped for now! :confused013:
 

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Wider is better on the air gap. To close will not let the sensor see the gap in the harmonic balencer.
 

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Wider is better on the air gap. To close will not let the sensor see the gap in the harmonic balencer.
Philip, This thread gave me bad flashbacks.:hehe:
 

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He had a crank sensor die a while back. I got a few PM's. That was to slow so we went to phone calls.

I helped getting him backup and running. :D
 

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i figured, just had to flip some crap. sorry, just the way i am, i blame my dad mostly:lol4:
 

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Discussion Starter · #12 ·
alright so i adjusted the cps to .050... checked the wires for it they seem fine... still no go... i also noticed im getting a draw off the battery when every thing is off.. went through the fuse panel in the truck and its nothing in there.. narrowed it down to a large black plug coming off the battery that goes into the main harness... does any one know of a decent wiring diagram for these things?
 

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He had a crank sensor die a while back. I got a few PM's. That was to slow so we went to phone calls.

I helped getting him backup and running. :D
Philip, did you ever mess with the junk one?

And by the way I still have your number.:party018:







.
 

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Yes I have played around with it. Now I need to get the one off that 92 and see if it is working.

Yours was switching. But it wasn't letting full voltage threw. It was only letting 1 volt threw.

After I do some testing with the other one. I'll do a little write up on how to test them. :D
 

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If the PCM doesn't see a RPM reading it will not turn on the auto shutdown relay. The ASD relay controlls the power to the alt and A/C compressor. .
I am having a similar issue. I have been reading posts for a few days...

From my research, mainly the FSM and the 92 Powertrain Diagnostic Procedures manual...

The ASD relay WILL send a signal to the PCM (Pin 51) about 10 Volts with only the key on, not engine running.

Since I'm highjacking a dead link, I have the same symptoms. No charging, Flashed code 41, and no power to either field wire.
-I have checked pins 3 and 9 for power @ PCM harness.
- The grid heater is working.
- Have power through ASD relay to the PCM harness.
- I've checked my grounds, Battery to engine and altenator case grounds are good. I couldn't find the ground that is under dash, right of steer colum, or the one at back of engine to firewall. I'm not too concerned about that.
- I took it to the shop and had it hooked up to the computer, my CPS is sending the signal.
- Finally, I jumper wired the alt. ( Thanks Steve G) Disconnected the field wires, jumper wired one field post to battery positive post. Other jumper wire to other field post, then started engine, with volt meter attached to battery, grounded the loose end of other jumper wire. No change in charge... (Should be over 14.5v) Leads me to believe the Alt is shot...

New Alt on order, will be in on Monday.... Still doesn't answer why I don't have power to either field post, with key on...

I have a suspicion that the voltage reg in the PCM is also at fault. I think I will be installing an external voltage reg as well.... ho hum...

I've never had A/C, nor do I need it, but I will check to see if the PCM is sending signals where it needs to go...

If anyone is listening, and has any thoughts, I'm all ears!
Thanks!
 
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