MEP-501A Voltage/Load Gauges Inop

[kubotaman]

Hi All,
Last year I picked up a MEP-501A with about 200 hours from a friend for charging trucks. It runs well and produces power as it should. However, I bought it with the voltage and load gauges not working. It came with a replacement voltage gauge and I just installed it and nothing changed. I checked the instrument panel fuse as per the TM but the fuse was fine.

I tried hooking up the old gauge to 24V and it showed no voltage and I assumed the old gauge was broken. Is it possible my new gauge is defective? Should I bench testing that one with 24V as well? Is there any other known culprits I should check before running down the checklist in the TM? Thanks

 

[Dieselmeister]

Since both gauges are not working, there is a possibility that the set is wired wrong, or has been "re-wired". Check your voltmeters with a power supply, or a 9 volt battery to se if they work. Don't check the load gauge with a battery or power supply. That gauge has a 50mv full scale deflection.
The MEP-531A ARMY TM 9-6115-673-13&P manual has the wiring diagrams in the back. You can use a voltmeter to check the voltages on the back of the meters while the set is running, and putting out power, to see if the meters are getting any power.