Battle-Tested Diesel Generators and Parts › Forums › Military Generator Troubleshooting › 815A Issue
Tagged: 400Hz, Frequency Problems, MEP815A
- This topic has 2 replies, 2 voices, and was last updated 8 years ago by eddieleneave.
May 17, 2015 at 10:36 am #2474eddieleneaveParticipant
I have a 815A 400hz Gen that I am working on and was able to get running and now is running quite well. I had to replace the GCU due to a crank/starting circuit issue. I haven’t made any adjustments to the GSU at this point. Once I got it running I noticed that the “under voltage” lamp was illuminated. When the generator Master Switch is turned back to the start position to activate the generator side of the unit the voltage gauge will show a voltage reading of 110v or 220v, which ever I chose by selection but I do not have a frequency reading, no hertz, just a voltage reading on the gauge. I did check the lugs to see if there was anything to read and there isn’t. I also checked the convince plug and nothing was there either. I did have a low voltage relay laying around and did a quick swap but that didn’t fix anything. Yes I was assuming the relay was good. I have fault traced about 40-50% of the wiring so far and up to this point I feel that the wiring is correct. I did notice that once you power the system down and the RPM’s start to decrease, at a certain RPM the frequency/hertz gauge will do a quick sweep spike on the gauge to 412 and then back to 388. I can fault trace more of the wiring if suggested to do so. I am at a stand still as to what could be the issue. The manuals that I have been able to find on this particular unit don’t offer a good diagnostic flow system. So with that said if any assistance could be given I would be greatly thankful.
May 18, 2015 at 10:01 am #2475GMGKeymaster
It’s impossible to have a valid voltage reading of 110/220 and have that same electrical source not have a Hz (frequency) reading (assuming AC power). Your unit is 400Hz, so you need to make sure that your multi-meter (and you must use a good multi-meter) can measure frequency in that range. The convenience outlet, I assume will be 110v at 60Hz. But you should focus on the main lugs. Confirm you are using a good multi-meter and not depending on the on-board meters, which can fail.
May 18, 2015 at 7:01 pm #2477eddieleneaveParticipant
Yes, you are correct, I was using the gauge on the gauge panel as a source because at the lugs I am not reading any voltage or hertz. So I was assuming something was being produced because depending on the setting I could see a 110 volt reading or a 220 volt reading, per the gauge. But no hertz on the frequency gauge. Also as mentioned in the initial message once the engine was running, the “LOW VOLTAGE” lamp was illuminated.
As far as meters go I am using a fluke 88 with a max capability of reading of 200Khtz. the meter works correctly as designed.
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