831a oil pressure switch problem solved

smokem joe

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My 831a has a Nason 1M-2B-15F/67 pressure switch with two terminals. The photos for both the 14 and 15psi switches described here look like there are 3 terminals. Have you received your order yet? How many terminals are there?
According to Nason's specs anything labeled 2B would be 1/8" NPT and SPST-NC. That would be 2 terminals. 2C would be the same size but with 3 terminals. I'm sure it could be made to work but why go through the trouble. See attached literature to decipher Nason part number.

Also, are you sure you have a 1M? I see no mention of this from Nason. They make a LM switch that is virtually identical to the SM line but no 1M.
 

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doghead

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Has anyone simply looked for the NSN from the parts manual, and looked for it?
 

smokem joe

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I did. I couldn't find it in stock anyplace other than GMG and no way was I going to pay $100 for this sensor. Other places had it available, but it was back-ordered till at least April. That's why I decided 1psi different was not a big deal.
 

doghead

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Could you post the nsn?
 

doghead

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I recall this same issue with Mep-002 and 003 gens too.

A generic switch was also the best option.
 

dav5

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I just took a look at the photo I took. I think it is MM and part of the first M is missing.IMG_0815.jpgIMG_0815.jpgIMG_0815.jpgNSN is 5930-01-478-0122 Green mountain is the only seller I can find at $98. Sorry about the triple image. uploading
 

smokem joe

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That is the same NSN I have. GMG crosses it over to Nason SM-2B-15F which is the same part number that is on both of the switches on mine. Nason does make MM switch with virtually same specs so that is probably what is shown in the pictures. Either the LM, MM, or SM switch would work as long as they have the correct electrical connection. They make them with a variety of options for hookup.
[h=1][/h]
 

smokem joe

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I wonder if a similar issue is causing the problems on these.

I did find also the switch on an 803a is a 2C from Nason and the third terminal just isn't used on those. Might work to test a unit in a pinch if you have both.
 

doghead

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Most likely, three terminal allows the choice of normally open and normally closed contacts.

Two terminal will not. It will be one or the other(as specified).
 

dav5

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Most likely, three terminal allows the choice of normally open and normally closed contacts.

Two terminal will not. It will be one or the other(as specified).
Yes the 2C is a SPDT and the 2B is a SPST according to the descriptions on the web sites. Here is the Davidsonsales switchnason.JPG
 

smokem joe

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I received my switch from Davidson today and installed it. Worked perfect! I can confirm it looks exactly like the picture and is indeed a two prong switch.
 

dav5

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I received my switch from Davidson today and installed it. Worked perfect! I can confirm it looks exactly like the picture and is indeed a two prong switch.
Thanks for the heads up. There website was not accepting orders a few days ago but I ordered two when it got fixed
 

dav5

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I wish the moderators would make a definite statement regarding what can be posted regarding parts for sale on various sites, generators for sale on the same sites. Are parts OK?????? Are generators OK?????
 

dav5

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For instance you aren't supposed to link to an auction "buy it now" but you can link to a company that has a fixed price? Doesn't make much sense to me.
 

doghead

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The rules are clearly explained in the RULES.

Read them all and ask in the website help forum if you still have trouble understanding something in particular.
 

dav5

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I read the RULES prior to commenting and I have no trouble understanding them.They don't make sense!!!!
I stand by my previous post
 
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doghead

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Stop hijacking this thread.
 

calsdad

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I picked up a pair of 831s from auction. I want to use one to run instead of the 803 for just a lighting load. Both were tier 2 reset and the hour meters on both read 2 hours and this matches the hour count on the reset tags. One unit starts and runs nicely and seems to function as it should. The other unit started and ran great until I shut it down to add more fuel. Upon restart the low oil pressure light stays on and it won't go to more than an idle. Also, the only way to shut it off now is to manually move the governor and shut it off. It worked perfect when it first started. What could have changed? Can someone point me to the correct troubleshooting procedure to figure out what is wrong with it?
Just wanted to give you and all the other people who responded to this thread a thumbs up. I've got two MEP-831a's - and I have been going thru one of them trying to make sure everything is working correctly. What I found was the thing would start up fine, seemed to run a bit slow - and then would not shut off. I checked all the governor adjustment stuff ( read a number of threads and followed the instructions) , but I still could not get the thing to shut off. The voltages at the governor control module were not right either. The thing is - I was working on the thing outside - in the sun - so I didn't notice that the oil warning light was on.


I had just changed the oil out - it looked sort of gunky, and I had removed the filter and checked that out too. So I was pretty sure the oil was good. The oil pressure switch though - kept seeping oil. I could not get it to stop. So I started getting suspicious that there might have something to do with what was going on. I did a quick search here - found this thread - and then I swapped over the pressure switch from my other set - and started the thing up - and now it appears to be working fine.

Weird thing is , with a good pressure switch in there, the RPM's are higher - it shuts off properly - and the light is out of course.
Seems like a bit of dopey design - to have the entire genset not work correctly because it's got a bad pressure switch.
 
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