MEP803A Over Voltage

TheAlfredo

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Miami, FL
I haven't looked at the TM yet. I was just on here making a different post and figured I'd ask away. I have an 803A that I purchased over a month ago. It started and ran great. Yesterday I was going though my generators, started and ran this one....but it started and turned off and overvoltage light stayed on. If I flip up the battle short when it starts, it stays on....but the voltage gage is pegged at 300V. I immediatly shut it down and haven't done any trouble shooting yet.
 

Light in the Dark

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Is it running at the correct speed? I had a set in that was displaying over voltage because someone had manipulated the throttle stops (so it WAS producing too much voltage).
 

TheAlfredo

Member
155
10
18
Location
Miami, FL
Is it running at the correct speed? I had a set in that was displaying over voltage because someone had manipulated the throttle stops (so it WAS producing too much voltage).
I believe it is.....because I starated it when I received it. I added fluids....started right up, rand for a while and I shut it down. Yesterday I went to start it to put a load bank on it, and it would start and shut itself down. Nothing has been manipulated since I received it.

I'm going trough the TM now but not finding that section.
 

Ray70

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Is the Hz gage at 60 approximately?
My first guess is a defective, damaged or otherwise "messed up" voltage adjustment Pot in the voltage regulator.
If you look at the VR you will see a small hole in the front cover with an adjustable potentiometer behind it.
I had a machine where someone tried playing with it and messed up the Pot and it caused the output voltage to go high.
Simply drill out the cover rivets and unsolder the potentiometer and replace with a new one.
It's probably about $1 for the component on-line.

Before doing this, make sure your AM/VM switch and AC select switch are not dirty inside . Spray some electronics cleaner or Detoxit and exercise the switches first. If no improvement test the VR.

You have another Pot on the front panel that attaches to the screws on the VR, but I don't know if that one could cause that much of a problem, it's like afine adjustment where the internal one is more of a coarse adjustment.
 

TheAlfredo

Member
155
10
18
Location
Miami, FL
Is the Hz gage at 60 approximately?
My first guess is a defective, damaged or otherwise "messed up" voltage adjustment Pot in the voltage regulator.
If you look at the VR you will see a small hole in the front cover with an adjustable potentiometer behind it.
I had a machine where someone tried playing with it and messed up the Pot and it caused the output voltage to go high.
Simply drill out the cover rivets and unsolder the potentiometer and replace with a new one.
It's probably about $1 for the component on-line.

Before doing this, make sure your AM/VM switch and AC select switch are not dirty inside . Spray some electronics cleaner or Detoxit and exercise the switches first. If no improvement test the VR.

You have another Pot on the front panel that attaches to the screws on the VR, but I don't know if that one could cause that much of a problem, it's like afine adjustment where the internal one is more of a coarse adjustment.
So today I drove out to where I have it stored. Started up...and again, shut down due to over voltage. I had my meter with me this time. I started it up and flipped the battle short for it to stay on. I checked voltage at the convenience Outlet and lugs....both less than a volt. Even though the generator gage was pegged.

I turned off the machine...took a phone call and restarted the machine. When it restarted....it was working fine and giving the correct voltage.

I'm puzzled to say the least.
 

Ray70

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I think the first thing you should do is give the AM/VM and AC select switches a good cleaning and exercise them a bit. Could be just oxidation on the contacts causing bad connections. There's lots of discussions here about the switches, what happens when they are dirty and how to clean them.
I'm especially leaning towards the AC select switch being dirty. To properly clean it you will need to remove the cover over the control cube and get some Detoxit or other good quality contact cleaner.
 

Light in the Dark

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Yeah invest in a bathtub full of a good quality contact cleaner (I like Deoxit better than CRC, but you use what you can get)... and just SOAK the switches with the batteries disconnected, and move them through their range until your elbow wants to give out. Surprising what this magic in a can is able to do.
 

Light in the Dark

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I turned off the machine...took a phone call and restarted the machine. When it restarted....it was working fine and giving the correct voltage.
This is the line that I come back to (and I am sure Ray did as well). Corrosion can put you in intermittent condition hell. I think if it was a failed component or setting with the VR, it would persist under all conditions.
 

TheAlfredo

Member
155
10
18
Location
Miami, FL
This is the line that I come back to (and I am sure Ray did as well). Corrosion can put you in intermittent condition hell. I think if it was a failed component or setting with the VR, it would persist under all conditions.
I’m think I’m going to tow it back to my house to give me something to do during lockdown.
 

TheAlfredo

Member
155
10
18
Location
Miami, FL
Update.
So I took the top cover off. The S8 switch looked perfect and clean. But I still sprayed it down and manipulated it back and forth. Over voltage would go away on a couple starts, then it would come back. Sprayed it down some more and it seemed to be working properly without the overvoltage. Today I went and started it up....Overvoltage again. Sprayed and moved the switch around and nothing. It sat for a while, went back to start it....and it started right up.

So I connected my load bank and ran it....ran perfectly. About 15 min in (estimate) Overvoltage and shut down. Did it a couple more times.

The fact that it runs...and then gets the overvoltage sound like it shouldn't be the switch.

Wondering if I should just swap out the Voltage Regulator since I have a new spare...I'll add the fuse while I'm at it?

Any other suggestions?
 

America

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Location
USA
Update.
So I took the top cover off. The S8 switch looked perfect and clean. But I still sprayed it down and manipulated it back and forth. Over voltage would go away on a couple starts, then it would come back. Sprayed it down some more and it seemed to be working properly without the overvoltage. Today I went and started it up....Overvoltage again. Sprayed and moved the switch around and nothing. It sat for a while, went back to start it....and it started right up.

So I connected my load bank and ran it....ran perfectly. About 15 min in (estimate) Overvoltage and shut down. Did it a couple more times.

The fact that it runs...and then gets the overvoltage sound like it shouldn't be the switch.

Wondering if I should just swap out the Voltage Regulator since I have a new spare...I'll add the fuse while I'm at it?

Any other suggestions?
Sounds like corrosion to me.
Update.
So I took the top cover off. The S8 switch looked perfect and clean. But I still sprayed it down and manipulated it back and forth. Over voltage would go away on a couple starts, then it would come back. Sprayed it down some more and it seemed to be working properly without the overvoltage. Today I went and started it up....Overvoltage again. Sprayed and moved the switch around and nothing. It sat for a while, went back to start it....and it started right up.

So I connected my load bank and ran it....ran perfectly. About 15 min in (estimate) Overvoltage and shut down. Did it a couple more times.

The fact that it runs...and then gets the overvoltage sound like it shouldn't be the switch.

Wondering if I should just swap out the Voltage Regulator since I have a new spare...I'll add the fuse while I'm at it?

Any other suggestions?
Honestly still sounds like something is dirty.
 

America

Member
75
35
18
Location
USA
I think the first thing you should do is give the AM/VM and AC select switches a good cleaning and exercise them a bit. Could be just oxidation on the contacts causing bad connections. There's lots of discussions here about the switches, what happens when they are dirty and how to clean them.
I'm especially leaning towards the AC select switch being dirty. To properly clean it you will need to remove the cover over the control cube and get some Detoxit or other good quality contact cleaner.
did you clean what ray suggested?
 

kloppk

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I'd suggest checking the connection between the front panel voltage adjust potentiometer and terminals 1 & 2 on the regulator. An intermittent connection there would cause random voltage swings. With the set OFF disconnect the leads to terminals 1 & 2 and measure the resistance bewteen the leads as you turn the potentiometer. It should vary smoothly from 0 to 5,000 ohms. If good reconnect the leads to the VR.
If that's solid I'd then check the connections to terminals 3 & 4 on the voltage regulator. This is were the regulator senses the output of the gen head. Intermittent connections to these terminals would cause the regulator to jack up the AC voltage should it see the 120 VAC drop out.

You might want to monitor the AC voltage on terminals 3 & 4 and see if it drops out when you get an overvoltage fault.

After that I'd suspect a flakey VR. I'd then swap in your spare VR and see if the issue goes away.
 

Ray70

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Make sure you also clean the AM/VM switch on the front panel. I'd also take Kurt's suggestion and closely monitor the output voltage and see if you are really getting a true over voltage condition or is it a false trigger caused by a bad connection, dirty contact etc.
 
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