Think I would check for voltage at the back of the alternator (big wire). If you have voltage there the fuse is fine. Tachometer working when the truck is running? I've got an external regulator I hook up to verify that the problem is in fact the pcm.

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Don't mean to hijack a thread. But I'm having a simular problem. With my half ton conversion. For all I know my voltage reg could be bad in the ecm. When I hook it the wires up my it will not charge at all. I tried the external regulator. It over charges the battery juicing 18v wile driving. My question is. The small wires to the regulator. One of the 2 should be hot with the key on correct? Thanks guys

 

Yes. If wired correctly it won't overcharge if the regulator is working correctly. Do you have a rpm/crank signal to the pcm?

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No I haven't got any kind of crank sensor or rpm signal to the ecm. I haven't messed with any of the tach or rpm yet. I wasnt sure if the 12v setup would communicate with the gasser ecm stuff. I have all gauges working except the rpm and temperature.

 

Must have tach signal to charge!

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Thanks mysterync did not know that. Any idea how to make a gasser ecm read the 12v tach. Is it possible. Thanks a lot for the info

 

I can't remember how the gas sensor/reluctor ring is cknfigured. I would vote it's got more notches. I'd probably just throw a manual regulator on it or switch pcm's. Just make sure the pin out is the same.
Is it an auto or manual?

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The 12v is manual the 1/2ton was auto

 

Might be easier just to use the external regulator but I'm pretty sure if the pinout matches you could use a diesel pcm and correct the charging issue.

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Well I ended up putting an external regulator on and the system is charging now but it is over charging the system. Now its at 18v at an idle. Any suggestions?

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The tach is working perfectly fine the only problem I have is the volt meter is only reading about 12v and my check engine light is on saying that my volts are to low on my charging system. So I ended up putting an external regulator on and the system is charging now but it is over charging the system. Now its at 18v at an idle. Any suggestions?