Diagnosing 200amp alt

[coachgeo]

transfered a 200amp hummer alt to my LMTV few years ago. All been good. All the sudden it has stopped charging. Does not reach 28v at bats (or on dash) and does not reach 14v.

Anyone have diagnostic hints?? like which one on this alt. is the excite wire? Figure will need to asses if it is getting 24v. I dont see labeling on anything but the 14v+ on side of regulator.

non related to this issue.. but future question... this alt is temperature sensing; if I understand right, and will dial back output to save itself. Is that correct? Where is the sensor? inside body of the regulator and it senses thru the contact of regulator to the alt. body orrrrrrrr??? wire to a sensor in the alt. orrr? But again.. this is secondary.. primary is checking to see if this one has failed me.

 

[Mogman]

The IGN terminal is clearly marked

 

[Mogman]

There are 3 terminals on the reg, 14V is the largest, IGN is the second largest and AC is the smallest terminal

 

[Mogman]

The red wire in this photo is the IGN terminal

 

[coachgeo]

The IGN terminal is clearly marked

nope..... no marks... at all. but before above postings in a review of a video that did show one marked... it appears that the one closest to corner on side of the regulator is IGN/excite and the AC as the one more central. That and was not sure if the IGN and the Excite is the same thing. Further reading clarified it was.

Sadly.. have full 24v at excite/ign with engine running.... but still no reading at at alt terminals with engine running beyond a reading of 12v at the 14v lug on the regulator and what I assume to be the 28v lug on the alternator. which I assume means no alternator output at all and just seeing battery voltage.

Any the assumptions above wrong? Suggestions for further testing?

 

[Mogman]

nope..... no marks... at all. but before above postings in a review of a video that did show one marked... it appears that the one closest to corner on side of the regulator is IGN/excite and the AC as the one more central. That and was not sure if the IGN and the Excite is the same thing. Further reading clarified it was.

Sadly.. have full 24v at excite/ign with engine running.... but still no reading at at alt terminals with engine running beyond a reading of 12v at the 14v lug on the regulator and what I assume to be the 28v lug on the alternator. which I assume means no alternator output at all and just seeing battery voltage.

Any the assumptions above wrong? Suggestions for further testing?

Most of the time, as in 95% it is the regulator.
BUT go through the testing/diagnosis procedures in the doc I posted for you before buying a regulator.

 

[coachgeo]

Most of the time, as in 95% it is the regulator.
BUT go through the testing/diagnosis procedures in the doc I posted for you before buying a regulator.

could be. troubleshooting doc says..... get another known working regulator to test the existing one lol. ohhhhhhhKKKKK like that is simple...

Anyone by miracle have a known working regulator for this beasty?

 

[Mogman]

could be. troubleshooting doc says..... get another known working regulator to test the existing one lol. ohhhhhhhKKKKK like that is simple...

Anyone by miracle have a known working regulator for this beasty?

That is fine as long as the thing that burned out your regulator was not the alternator, regulators are fairly plentiful but not cheap.

 

[coachgeo]

one other symptom.... on occasion it will jump to 26ish volt on dash when driving then go away 5 to 20 min later. does that sound like alternator or regulator?

 

[Coug]

to me definitely sounds like regulator.

Really in the troubleshooting guide, if it's passed all the tests for the alternator portion, and you're to the "swap on a new regulator to test" it's almost guaranteed to be a bad regulator. The tests are more to tell you if the alternator is good or not, and the assumption is if the alt is good, the reg is bad.
I suppose it might have a flying short or open in it where it inly fails during operation, but those are extremely rare.