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Mopar1973Man

Alternator & PCM failure

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6 minutes ago, Marcus2000monster said:

I can’t open it myself?

 

Not really, if you do you warp the aluminum case. I started to do the same thing but the case distorts rather easy trying to pry the cover off the sealant. 

 

6 minutes ago, Marcus2000monster said:

Is they’re anything else I should check or try before I send it off?

 

Not really the +12V is no longer coming from the PCM with the engine running so more than likely the PCM has taken damage. How much we don't know without getting it opened up inspected and tested. 

 

6 minutes ago, Marcus2000monster said:

Also what caused the alt to burn up?

 

The alternator armature shorted to ground on the blue wire. The fuse that protects the PCM also protects the ECM and VP44 which is a 20 amp fuse. The PCB fails before the fuse does.

 

This why so many did the external mod but this will only band-aid the system. Still will cause battery failure because most don't install the external properly based on under hood temperature. If you mount the external to close to heat it will undercharge. If it mounted to close to the outside cold it will overcharge and boil the batteries dry. This why I don't suggest this mod. The external regular bases charge voltage based on case temperature not battery temperature like the PCM.

Edited by Mopar1973Man
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1 minute ago, Marcus2000monster said:

Also can I drive the truck with he alt unhooked?

 

Yes, you can drive it but you better have a generator and a battery charger with you. Once the voltage falls below 12.00 to 11.99 then the volt gauge will fall to 8 and chime the check gage light.

 

2 minutes ago, Marcus2000monster said:

Are we just making sure it is hooked up or testing with multimeter?

 

There is only two things the alternator needs...

  1. +12V on the blue wire when the engine is running.
  2. GROUND on the green wire when the engine is running. 

If either of those is missing the alternator doesn't charge. Beyond that, the diodes convert the AC waveform to DC power. Sends it to the battery. The PCM controls only the GREEN wire for the variable ground to control charging voltage. 

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1 minute ago, Mopar1973Man said:

 

Yes, you can drive it but you better have a generator and a battery charger with you. Once the voltage falls below 12.00 to 11.99 then the volt gauge will fall to 8 and chime the check gage light.

 

 

There is only two things the alternator needs...

  1. +12V on the blue wire when the engine is running.
  2. GROUND on the green wire when the engine is running. 

If either of those is missing the alternator doesn't charge. Beyond that, the diodes convert the AC waveform to DC power. Sends it to the battery. The PCM controls only the GREEN wire for the variable ground to control charging voltage. 

Ok so how to test the ground? And I test with the mm on ac correct?

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Update for everyone. Mike and I talked over he phone and we concluded that they’re IS power to the alt wires which means pcm is working. My concern is that even though we have power to the wires that they're is still damages to the voltage regulator. Is it possible to have power but still have a damaged voltage regulator? 

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Sure thing. Not much more than the reman. 176.88 to be exact. Also is it possible to have power to the alternator and still have voltage regulator damage? My worry is that although i have power and ground the VR is still damaged and is gonna burn up more alternators. Might be a case of try and find out. How to perform a bench test for AC noise? Must theyre be battery hooked up or just need a multimeter hooked to negative post?

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12 minutes ago, Marcus2000monster said:

My worry is that although i have power and ground the VR is still damaged and is gonna burn up more alternators.

 

The only way that will happen is if the alternator is already damaged. This is why I always suggest bench testing before leaving the store. If you to just wire up +12V to the field and no regulator it would just run wild and overcharge but do no damage to the alternator or the PCM. Make sure that neither the blue or green wire is shorted to ground. That's all there is to it. 

 

This charging system has been around since the early 1960s. Dodge has really changed it much over the years. Even my old 1972 Dodge Power Wagon used the same 2 wire setup.

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7 minutes ago, Marcus2000monster said:

Mike how do I bench test the new alternator separate from the truck?

 

Good thing... The one I got was failed in the box. I've got a second one now and it good. Not the first time I've seen bad alternators in the box.

 

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2 minutes ago, Marcus2000monster said:

Got the new alt on and drove 30 miles with no issues so far. Got to get that fuse setup in and cover my butt now. 

 

Remember the fuse needs to be on the BLUE WIRE....

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Just now, Mopar1973Man said:

 

Remember the fuse needs to be on the BLUE WIRE....

Haha you got that typed up like a second before I posted this.

 

Just now, Marcus2000monster said:

So for the fuse I just need an in-line fuse holder and a 7.5 amp fuse wired into the green or blue wire on the field plug?

 

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Only the BLUE wire gets the fuse. 

 

Green can be shorted to ground and no harm will happen. It just makes the alternator overcharge. 

 

Short the blue wire to ground and you get the burned up PCM like me. 

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2 minutes ago, Mopar1973Man said:

Only the BLUE wire gets the fuse. 

 

Green can be shorted to ground and no harm will happen. It just makes the alternator overcharge. 

 

Short the blue wire to ground and you get the burned up PCM like me. 

I’m lucky I didn’t suffer PCM damage. So far everything is swell. Charging at 14.4 volts. 

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