MEP-806A won’t flash/excite

[Billy2642]

So I have an 806a with about 300 hours on it. Machine starts up and runs great. Once running, it shows about 49 hertz and 80 volts with an undervoltage light on. With that I figure it just has to be excited so I turn the start switch to start for a couple seconds and nothing. Gauges dont bounce or anything. Tried it with the battle short on and no change. Checked all the fuses under the panel and changed them out just in case. One thing I noticed is the alt gauge is only showing it charging at +3 volts. Is that enough power to pull to the windings to excite the system? I’m going to clean the magnetic pickup tomorrow and make sure it’s adjusted properly but I’m having my doubts that will work. Machine seems to be running at full rpm. The potentiometer for the hertz/frequency does adjust the rpm slightly. 50/60 hertz switch is on 60. Any ideas?

 

[metalchips]

I've had a lot of alternator issues with my 806a in the past and I would always find these kind of numbers when the DC control power dropped below around 15 volts. This was caused by the batteries being close to dead. Poke around with your multimeter and make sure that you have 24DC at the governor and 24VAC at the voltage controller. Look for loose ground connections. There's a test in the TM for the voltage regulator, make sure it's flashing the genset.

Evan

 

[Billy2642]

I've had a lot of alternator issues with my 806a in the past and I would always find these kind of numbers when the DC control power dropped below around 15 volts. This was caused by the batteries being close to dead. Poke around with your multimeter and make sure that you have 24DC at the governor and 24VAC at the voltage controller. Look for loose ground connections. There's a test in the TM for the voltage regulator, make sure it's flashing the genset.

Evan

Took the alternator to a shop, they said it tested great as if it’s brand new. I swapped the VR with a known good one and nothing changed. I do have 24vdc where you mentioned. Any other ideas?

 

[155mm]

Am I missing something here, the batteries should have 24vdc, but if the engine is running it should be 27.5-28.5.

 

[Billy2642]

Am I missing something here, the batteries should have 24vdc, but if the engine is running it should be 27.5-28.5.

Yes. I have verified that it’s running about 1800 rpm