Quicky LP question (aka is Cummins nuts?)
03-20-2004, 07:34 PM
#16
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Ok, well this thread is taking a turn... neat...
Why am I'm trying to blow up my PCM? I'll tell ya...
In the middle of a cold morning, far from anywhere, I had a truck that wasn't charging. In hindsight this turned out to be brushes, so the there was a break in the ciruit between the high and low field wires. Of course older alternators will complete this circuit to ground and are regulated by controlling the voltage on the positive side, and often the second wire is (or can be) used for some other function (which is why you only need a single tap to full-field).
However, in the Dodge (and maybe other newer cars), it seems that a full 12v is applied to the high side all the time and the low side is regulated (I figured via resistance but this pulsing mentioned above may be the case and would work).
20 years of working on cars, and I automatically ASSume that the high side is regulated and 12v should be applied. Of course, being that in this sceneio 12v is already naturally there, it does nothing, which leads me to believe that I've tapped the wrong wire (also figuring that 12v to the wrong wire for 1/4 second won't harm any regulator), so I tap 12v to the other wire thinking I (and my test light) made the wrong choice. This gave 12v to the PCM and toasted it.
Now this thread is getting interesting because there is the off chance that in the wee hours, that I might have shorted the leads and cooked a diode in the alternator, but the odd part is that after replacing the brushes, the alternator would *over* charge when normally connected to the PCM. ???? ???? ????
Being that this system is so backwards (to me), I suppose if I reverse everything, that the PCM could still be OK and that applying 12v (or possibly shorting the high and low side) could have bridged a resistor in the alternator that is now acting like a dead short. A small chance indeed, but I'll go purchase new alternator and hook it up for kicks.
The inclination to even try this comes from "Haulin in Dixie"'s insistance that the alternator does indeed respond as a normal alternator would...which mine isn't doing. Perhaps more than the brushes went wrong with that unit that night, but I wouldn't think that overcharging would be the result, so I leaned towards PCM.
Interesting
Sean
Why am I'm trying to blow up my PCM? I'll tell ya...
In the middle of a cold morning, far from anywhere, I had a truck that wasn't charging. In hindsight this turned out to be brushes, so the there was a break in the ciruit between the high and low field wires. Of course older alternators will complete this circuit to ground and are regulated by controlling the voltage on the positive side, and often the second wire is (or can be) used for some other function (which is why you only need a single tap to full-field).
However, in the Dodge (and maybe other newer cars), it seems that a full 12v is applied to the high side all the time and the low side is regulated (I figured via resistance but this pulsing mentioned above may be the case and would work).
20 years of working on cars, and I automatically ASSume that the high side is regulated and 12v should be applied. Of course, being that in this sceneio 12v is already naturally there, it does nothing, which leads me to believe that I've tapped the wrong wire (also figuring that 12v to the wrong wire for 1/4 second won't harm any regulator), so I tap 12v to the other wire thinking I (and my test light) made the wrong choice. This gave 12v to the PCM and toasted it.
Now this thread is getting interesting because there is the off chance that in the wee hours, that I might have shorted the leads and cooked a diode in the alternator, but the odd part is that after replacing the brushes, the alternator would *over* charge when normally connected to the PCM. ???? ???? ????
Being that this system is so backwards (to me), I suppose if I reverse everything, that the PCM could still be OK and that applying 12v (or possibly shorting the high and low side) could have bridged a resistor in the alternator that is now acting like a dead short. A small chance indeed, but I'll go purchase new alternator and hook it up for kicks.
The inclination to even try this comes from "Haulin in Dixie"'s insistance that the alternator does indeed respond as a normal alternator would...which mine isn't doing. Perhaps more than the brushes went wrong with that unit that night, but I wouldn't think that overcharging would be the result, so I leaned towards PCM.
Interesting
Sean
03-20-2004, 08:03 PM
#17
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haha, maybe he was talkin to me since i asked how it was done :P and no. wouldnt want to do this. SOunds bad haha. But, going to school for diesel Tech, just went thorugh charging systems and didnt recongnize this ( not that im a pro or nething. Im just learning as much as i can) But i can see one thing it comes in handy for, winches. use this idea to run those darn things haha
03-21-2004, 11:07 AM
#18
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Please disconnect the pcm terminals at the alternator before adding voltage. One to ground and one to 12v will give you full output if the alternator is working. Forget about which terminal does which, it does not matter to the alternator.
The electronic regulator (two wire) sets one terminal to 12v+ and regulates the other for the voltage. Looks like you are trying to second guess the pcm and later the regulator. Here is a copy of an earlier post on this subject.
Setting it up is real simple. You have two connectors on the alternator field and two on the regulator. Hook the two alternator terminals to the two on the regulator. Does not matter which one on either. There is just one more connection. The regulator terminals are on a small triangle mounting. Originally the Chrysler products had three terminals here, but the later ones only had two. One terminal is centered at the top of the triangle; connect this one to the ignition on circuit. That’s it, real simple.
This is a lot easier to set up than the old three terminal or grounded field types. The regulator that I used is for a 1979 D-100 pickup.
The electronic regulator (two wire) sets one terminal to 12v+ and regulates the other for the voltage. Looks like you are trying to second guess the pcm and later the regulator. Here is a copy of an earlier post on this subject.
Setting it up is real simple. You have two connectors on the alternator field and two on the regulator. Hook the two alternator terminals to the two on the regulator. Does not matter which one on either. There is just one more connection. The regulator terminals are on a small triangle mounting. Originally the Chrysler products had three terminals here, but the later ones only had two. One terminal is centered at the top of the triangle; connect this one to the ignition on circuit. That’s it, real simple.
This is a lot easier to set up than the old three terminal or grounded field types. The regulator that I used is for a 1979 D-100 pickup.
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