MEP 831A voltage gauge

[grywitt]

Hello.
I did end up getting an 831A and the inverter even works. Rats had lived in it and chewed through the fuel pump wire and were making nest material from the insulation but really not bad shape once cleaned up. My question is about the voltage meter. This one peggs all the way to the right when it's running but comes back to zero when not running. So it works ish. I have verified 240 volts with my fluke. I bought a different guage off ebay and it was very faded and discolored but that wasn't the problem. Once I went to fine tune the voltage reading the plastic adjustment on the front of the meter disintegrated and my screwdriver went right into the guage. Lol. Oops. Okay so back to my guage. It has moisture in it. Every day the glass has moisture on it. I'm wondering if that has something to do with it maxing out when voltage is applied. It says it's sealed on the back and the fact that the moisture isn't drying even though we are having 100+ degree days with low humidity here in south east NM. I believe it. Finally my question is has anyone looked inside one of these and might know where the safe place to drill a small hole in the case to let the moisture dry out then I could seal it with a dab of silicone once it's dry. I just don't want to drill into it and mess up the works inside it. Does anyone know a reason I shouldn't do that? It works enough now to indicate voltage just not set it.

 

[kloppk]

As I recall the meter back is secured to the body of the meter by a threaded ring that screws into the black body of the meter. You need to have the meter removed to see it. If not to corroded you can use a small screwdriver and small hammer to unscrew the ring. The ring has small notches in it to place the screwdriver tip.
As I recall there is a sealing gasket between the meter back and the meter body. It probably dried out letting moisture in.

 

[fb40dash5]

Can confirm what Kurt remembers from messing with mine. Remove the gauge, and unscrew the ring from the back with a hammer & chisel. The seal in mine (which seemed to basically have been an old red rubber band) had actually fallen out at the top & was physically blocking the needle from moving freely.

I figured "sealed- do not disassemble" was neat in theory but I couldn't break it more than broken. I reassembled mine with a very thin bead of RTV.

As I recall, there's no need to mess with the nuts & stuff at the back of the case, that just allows removing the action from the cup one you have the glass face off.

 

[Guyfang]

We found that when the temperature raises, the moisture condenses on the glass.

 

[grywitt]

Thanks guys. I will try to unthread it rather than drill. I did try a little when I had it in my hand but not very hard. I'm not sure the moisture is the problem but it can't be helping. The gauge does indicate voltage but it just pegs all the way to the right. I haven't tried setting the inverter to 120 to see if it still goes all the way but I probably will soon. Thanks again for the info.