MEP 005a Low oil pressure light on unit still running?

[leedawg]

So I went out to start the generator today. Its been pouring rain the last 4 days over here. Turned the switch on and usually just the low oil pressure light comes on and thats it but clears itself when you start the unit. Well today the top two lights came on low oil and cant remember what the other one is, then the top two lights in the generator section were on as well Think one is reverse current and the other something else. Any way hit the clear switch they all light up but they do the four do not clear. Started up the set runs fine makes power everything seems normal. There is oil pressure according to the gauge.

Hit the clear button on the warning announciator panel all the lights came on then let go just the low oil pressure light stays on really strange. However the generator keeps running even with the red light on.

So my question is if any of you have experience with this. I was under the impression when something comes on that panel and lights up the set shuts down automatically. I checked the battle short switch and it is off so the set is in normal operation mode.

I am wondering if there are some relays or something that just light up the announciator panel lights that are stuck closed from moisture or something like that. Looks like quite the problem to track down. Its been fine till yesterday this problem started. Next weekend I plan on pulling the module out and opening it up to see what is inside of it.

Got to pour through the TM some as well im sure to start tracking down all the safety circuits and test them well at least the engine ones that I can test.

 

[1800 Diesel]

leedawg,

Could be the "special relay assembly" malfunctioning or one of the other relays. I might try swapping out the oil pressure switch with a known good one and always check terminal connections.

Sewerzuk knows a lot about those models & hopefully he can assist. Good luck with it.

 

[leedawg]

Well just an update. More for the people that happen to search this sometime in the future so they have some follow up.

I localized the problem of the fault indicator panel. IT appears to be just in the panel itself the fault sensors all work fine and shut the set down. ( Tested them all)

So I took the panel out and hooked it up to another set same lights were on, on that set. So I opened it up and took it apart. There is a PCB (well its not really its more of a fiberglass board holding some pegs that have resistors, capacitors, and thyrosistors soldered onto it.

So everything is well attached all the resistors checked out, the capacitors checked out. So I did not feel like desoldering everything to test the SCR's. But the basic concept of them is they are sort of like two transistors tied together to act as a latching relay. So Power will not flow across them till a voltage is applied to the gate pin then current will flow across the cathod and anode even if the power is removed from the gate pin the power will continue to flow. Hence sort of like a latching relay and the fault light stays lite after its triggered until the reset relay resets power to the SCR.

Well there was a lot of moisture in the panel from all the rain we have been having after being out in the sun for about and hour all the problems self corrected when I re installed the panel. So I imagine the resin layer on the components is probably breaking down after 30 years and the moisture is probably creating enough of a path to trigger the gate pins on the SCR's.

Panel works just as it should now so I put it all back together re installed it and will await the next rains to see what happens. If it gives more problems Im probably going to recoate it with some more resin over all the components and see if that does not straighten it out. Thanks for the one reply

 

[1800 Diesel]

leedawg,

Glad you got it figured out. Does the genset stay outside with no cover? Even if it stays in the shed, a 25-watt incandescent trouble light inside the cabinet will go a long way in keeping humidity down. In my old shop, I keep a 15-watt bulb going inside an insulated shipping crate to keep my welding rods dry & it works great. If the unit has to stay in the rain I can give you a few other ideas too. Not having our new shop completed yet has forced us to set up "tarp tents" in the woods and they work great. Real simple to rig up too...

 

[leedawg]

yup its just sitting outside next to the barn in the rain. I thought these things could be outside in the elements with the cabinets they are in. I had thought about putting a little space heater inside the cabinet but I like your idea of a light bulb. Id love to hear more about what you do for outside though. Thanks again.

Lee

 

[rickf]

I saw some stuff in the electronics lab at the college I work at for spraying on those boards to seal them, I will send myself an e-mail to check it out on Monday and report the name of it. Sounds like if you can just reseal the board it would solve the problem.

Rick

 

[leedawg]

I saw some stuff in the electronics lab at the college I work at for spraying on those boards to seal them, I will send myself an e-mail to check it out on Monday and report the name of it. Sounds like if you can just reseal the board it would solve the problem.

Rick

Thanks rick yeah appreciate it that sounds like the ticket for sure. Ill just dry it out real well again in the sun or with a hair dryer then spray the sealant onto the board and it ought to solve the problem. Let me know Monday what you find thanks again for all the responses.

Lee

 

[rickf]

If it is not out in the open I will have to wait until I can catch one of the professors. You might find something in Radio Shack or one of the online electronics stores. I should be able to catch one of them in, it is finals time. 3,000 stressed out students running around in a daze.opcorn:

 

[Triple Jim]

It's my opinion that special conformal coatings for protecting circuit boards are often not very different from common clear spray enamel coatings like Krylon. On another forum, I read that an engineer at Krylon said their conformal coating and their clear enamel appeared to be the same, but wouldn't quite come out and say they were identical with different labelling. Hearsay, but enough to make me try the cheap version on some boards I'm making.

 

[rickf]

I was going to say that I have used clear lacquer paint in the past but that was for my own stuff and did not want to volunteer info that might not be proper. I did find some info on conformal coatings just doing a search for "circuit board spray".

http://www.productionsupplysolutions.com/Circuit-Board-Coatings-s/4.htm

 

[PeterD]

It is called conformal coating... Today it is either an epoxy or a polyester resin, but years ago it was a lacquer or varnish. Virtually everything in the military used the stuff (we hated it, made replacing components a real PITA, and then you had to brush more on to protect the repaired area!)

Interesting enough is that my MEP-004a was sitting out and was very damp inside the case when I went to do a runup and test. It ran for about three or four minutes without a load (I had gone in to get the heaters) when I heard it shut off. I came out thinking the worst. I noted the overvoltage light was on, so I reset it and tried a restart. It restarted just fine and I tossed a load on it and again left it to run. Ran for the 30 or so minutes I'd intended without any further problems. I'm sure the excess dampness was responsible but I don't know if the problem was a true over voltage or if the sensing/fault circuit was the problem. No question these older generators (mine is a 1990 vintage) do have some sensitivity to dampness. Next year I'm going to improve my water-proofing to try and keep it more dry when it rains.

 

[rickf]

Thanks rick yeah appreciate it that sounds like the ticket for sure. Ill just dry it out real well again in the sun or with a hair dryer then spray the sealant onto the board and it ought to solve the problem. Let me know Monday what you find thanks again for all the responses.

Lee

Dredging this one up from the past, I just found some stuff that would be perfect for the situation we were talking about with the wet boards.
Dang, I just realized it is a E-bay link! Give me a bit if time to figure out how to get the info to you all without violating the policies here. This exactly what we need on any outdoor electronics. It is made for marine electronics.

Rick

OK, Went directly to their site and here is the stuff.
http://www.aeromarineproducts.com/electronic-potting.htm