MEP-005A Over Voltage Problem

[flydude92]

I purchased a working MEP-005A in August 2012 and put about 10 additional hours on it.
It has worked very well until now.

Every month I run it for about an hour to make sure everything works. On 2/1/13 it ran for about 10
seconds with proper voltage and frequency when the over voltage light went on. The voltage meter
jumped to about 160 volts and the generator didn’t shut down as expected.

I shut it down, checked connections and anything else I could come up with and restarted it.
It immediately went to an overvoltage condition and kept running.

I went inside (it was 25 degrees out & windy) and read thru the TM’s looking for anything to check out.
About an hour later I started it again and it ran about 10 seconds with proper voltage and frequency and
then the overvoltage light came on. The generators frequency meter stopped working the day I got it
home so I purchased a Hardy Diesel volt/hz gauge. This gauge was unreadable at the higher voltage.

At this point I thought it might be a moisture problem since I saw a lot of moisture in it a couple days
earlier. I brought the exciter/voltage regulator assembly in the house, checked it out for obvious
problems and tightened a few screws. I noticed some white powder corrosion on some of the diodes
on the VR board that I cleaned off.

A couple days later I reinstalled the exciter/voltage regulator. The generator ran perfectly for about
10 minutes then the voltage meter jumped a couple times, the overvoltage light came on and the
generator kept running.

At the convenience outlet the voltage was about 160 volts and the frequency was about 245 Hz.
The engine was running strong and steady with no speed variations.

I checked with William at Delk’s. He had me disconnect the exciter/voltage regulator and apply 12V
to wires F1 & F2 of the generator. He was expecting 90-120V at the convenience outlet. I received
167v. (I can’t find any of this information in the TM’s) Thinking I might have a bad diode/rectifier on the
generator I removed them. I don’t have a diode checker but they averaged .55 ohms in one direction
and none were shorted.

The problem I am having might be a heat/cold sensitive component, vibration sensitive or one that
breaks down under load. Or a loose connection, although I haven’t found one yet. So I plan to replace
the diodes and go from there. The TM’s say they are 1N1190 & 1N1190R diodes. The only number I can
get off of one diode is 3A699E01. I Can’t find a reference for this.

Can anyone tell me if this is a normal reading for these diodes and give me any suggestions of where to
look next? At some point I will also have to figure out why the generator didn’t shut off on its own but I
thought I would fix the voltage problem first.

Thanks, Brian

 

[Triple Jim]

At the convenience outlet the voltage was about 160 volts and the frequency was about 245 Hz.

Brian, either that's a typo, or something's wrong here. That's a 60 Hz generator, and it can't be that far off.

 

[flydude92]

It is a cheap meter and all I had left to read the frequency with but it did read my house frequency correctly. The Hardy Diesel meter stopped working when the voltage went up that high so I don't have another meter.
I may have read it wrong but at this point I will try to deal with the voltage problem. I was rushing to get back into the house due to the cold.
Brian

 

[PeterD]

...
Every month I run it for about an hour to make sure everything works. On 2/1/13 it ran for about 10
seconds with proper voltage and frequency when the over voltage light went on. The voltage meter
jumped to about 160 volts and the generator didn’t shut down as expected.
...

It is supposed to shut down, my MEP-004 did this on my last run-up though I don't know how high it got as I was headed in to get my load heaters. In my case I'm sure it was because of moisture (it was very damp inside the generator set) and when I started up again, it ran flawlessly for the remainder of my 30 minute test.

As for diodes being bad, AFAIK, any failure there will result in lower voltage, and not higher volts. I suspect there is something else (perhaps a bad connection at the voltage select board) that is the flaw allowing phase to phase leakage.

 

[flydude92]

It is supposed to shut down but didn't. It seems I have more than one problem to look into. I can fix most anything after I figure out how it works. I haven't had a generator before so I have a lot to learn.
In the mean time I am going by what other more knowledgeable people tell me. Since I removed the diodes I will replace them with new ones to at least eliminate them. That won’t happen until next week unless I can find a local source for them. I will check into the voltage select board as you suggest and look for problems there. I did convert the generator to single phase using sewerzuks procedure. Thanks, Brian

 

[leedawg]

It is supposed to shut down but didn't. It seems I have more than one problem to look into. I can fix most anything after I figure out how it works. I haven't had a generator before so I have a lot to learn.
In the mean time I am going by what other more knowledgeable people tell me. Since I removed the diodes I will replace them with new ones to at least eliminate them. That won’t happen until next week unless I can find a local source for them. I will check into the voltage select board as you suggest and look for problems there. I did convert the generator to single phase using sewerzuks procedure. Thanks, Brian

Anything Gen related and not engine related does not shut down the generator it just opens up the main breaker on the unit to protect your load. So how do you know it did not work right sounds like you were just looking at the convince outlet... Did the orange light on the breaker remain on in the high voltage state? It should not have it should have opened the main contactor immediately when it sensed over voltage.

I to have one of the hardy diesel meters on my unit. Im confused what happened to it are you saying you fried it somehow at 167 volts? Thats really not that high. That meter should be able to ready 240 no problem...

Your FQ reading sounds very suspicious to me Id go look into a slightly higher quality multi meter. Its physically impossible for your fq to be as high as you said if the motor is running "strong and steady." Fq is a function of motor RPM that is directly proportional with a multiplier of how many wingdings are inside the gen head.

This for sure sounds like a problem with the VR board however. I know on my own mep 5 one of them is pretty sensitive to moisture in the fault indicator panel and a bunch of the lights light up when it is moist inside this box.

Id suggest you place a space heater inside the cabinet for a couple of hours on full power get it nice and hot in there I atually put one sitting on top of the VR box. Let it really dry it out with the heat. Then go out and run it again and see if your problems dont go away. If they do then we know we need to think about re varnishing all the electronics on the VR board and maybe the transformer in there as well. That is where I would start at least.

I am in no where near as harsh of conditions as you are so I cannot speak on performance in those temp ranges. Have you run this unit before though when the weather was like this or is this the first time?

let us know.

 

[PeterD]

Anything Gen related and not engine related does not shut down the generator it just opens up the main breaker on the unit to protect your load...

Actually in my case it did shut down the generator. I'll have to check the manual to see what the expected action is on over voltage is, however.

 

[leedawg]

Actually in my case it did shut down the generator. I'll have to check the manual to see what the expected action is on over voltage is, however.

Hum interesting well I may stand corrected then.

I have had a short circuit fault when I popped the breaker in on my convince outlet (Somebody had wired the hot to the neutral) That popped the main breaker right off immediately, and ive had an overvoltage fault as well same thing. So I was under the impression it was just on the main breaker safety and would keep the motor running.

Now that you mention it however I do recall one of Swezurks videos him saying he had an overvoltage issue possibly due to rpm or something and I do not recall if that was shutting his rig down or not at that time.

 

[flydude92]

Anything Gen related and not engine related does not shut down the generator it just opens up the main breaker on the unit to protect your load. So how do you know it did not work right sounds like you were just looking at the convince outlet... Did the orange light on the breaker remain on in the high voltage state? It should not have it should have opened the main contactor immediately when it sensed over voltage.

I to have one of the hardy diesel meters on my unit. Im confused what happened to it are you saying you fried it somehow at 167 volts? Thats really not that high. That meter should be able to ready 240 no problem...

Your FQ reading sounds very suspicious to me Id go look into a slightly higher quality multi meter. Its physically impossible for your fq to be as high as you said if the motor is running "strong and steady." Fq is a function of motor RPM that is directly proportional with a multiplier of how many wingdings are inside the gen head.

This for sure sounds like a problem with the VR board however. I know on my own mep 5 one of them is pretty sensitive to moisture in the fault indicator panel and a bunch of the lights light up when it is moist inside this box.

Id suggest you place a space heater inside the cabinet for a couple of hours on full power get it nice and hot in there I atually put one sitting on top of the VR box. Let it really dry it out with the heat. Then go out and run it again and see if your problems dont go away. If they do then we know we need to think about re varnishing all the electronics on the VR board and maybe the transformer in there as well. That is where I would start at least.

I am in no where near as harsh of conditions as you are so I cannot speak on performance in those temp ranges. Have you run this unit before though when the weather was like this or is this the first time?

let us know.

According to the TM's it is suppose to shut down the generator and open the contactor. On the second try I turned on the main breaker and it didn't shut off when the voltage jumped. The Hardy Diesel meter didn't fry. I tried it in the house after my problems and it worked fine. When I plugged it back into the generator during high voltage it wouldn't work at all. I have no clue why. I did run the generator the previous month in 20 degree weather with no problems. It ran over an hour connected to the house and in fact it started very easily.
After the initial problem I brought the exciter/Vr box in the house made sure it was dry and left it in the house for 2 days. I didn't do anything to the rest of the generator since it
looked dry inside. I reinstalled the box and started the generator and it worked fine for about 10 minutes before failure.
I plan on installing a bulb in the generator as suggested soon.
Brian

 

[leedawg]

Well sounds like there are a couple things going on then I wonder why it's not shutting down in addition to the vr problem. I stand corrected on the faults you are right it is supposed to to shut down which makes me wonder why mine is not lol.

I would for sure try putting the space heater in there and getting the whole gen up to 80 degrees for a few hours then see if your problem goes away.

Sure sounds like it's in the vr box though...

 

[flydude92]

Well sounds like there are a couple things going on then I wonder why it's not shutting down in addition to the vr problem. I stand corrected on the faults you are right it is supposed to to shut down which makes me wonder why mine is not lol.

I would for sure try putting the space heater in there and getting the whole gen up to 80 degrees for a few hours then see if your problem goes away.

Sure sounds like it's in the vr box though...

First of all, thanks for telling me I was right. I wasn't expecting to be right about anything while I learned how to repair this generator.

After I get the diodes replaced next week I will warm it up for sure. You may be right about the VR box. When I get it back together and it doesn't work I will look at that more closely.

FYI: I removed the tactical relay box and checked it out. It looks new in there. I found a loose screw on the overload protective device. The overvoltage relay was loose in the box. The screws were tight
but all the inserts at the bottom of the relay box came loose so I glued them back in. Also, there was some corrosion under all the eyelets on the overvoltage relay.

Thanks to everyone for all the feedback so far. I will advise if I find anything new.

Thanks, Brian

 

[flydude92]

Update: I replaced the diodes in the generator and they didn’t fix the problem. I tried heating the generator to remove moisture without success. I decided it would be a
good idea to find out why it isn’t shutting off while I still have a voltage problem. I checked for voltage going into the over voltage relay and was getting 180V. I checked
for 28V going to the relay contacts and it registered 0V. I disconnected one wire from the relay and registered 28V on the wires. This tells me that something in the over
voltage relay is bringing down the voltage. The odd thing is that when I touched the disconnected wire to the relay for a second the voltage dropped to 2V and stayed
there for a couple minutes before it corrected itself. The relay assembly looks fine but I don’t have any diagrams for it.

Anyway, it sounds like the voltage problem is the voltage regulator as others have mentioned. Some of the diodes on the regulator are badly corroded so I will start there.
I included a picture of them. Buying replacement boards or having them repaired is reaaaaaaaally expensive so trying to repair this one seems like a good option for now.
I don’t have a replacement for the over voltage relay and hate to buy one to find out it wasn’t the problem but we will see.

The one thing I am thankful for is that this generator failed before I connected it to the house. That would have been a mess.

Does anyone know an easy way to test the backup systems on this generator? The TM’s only mention out of circuit testing requiring equipment I don’t have.

Thanks,
Brian

 

[PeterD]

A thought would be to get some brake cleaner and scrub that board as clean as possible.

 

[flydude92]

A thought would be to get some brake cleaner and scrub that board as clean as possible.

Would brake cleaner remove the coating on the board?

 

[skidunits4you]

It could I would use Electric contact cleaner. You can get it at parts stores. Also depending on weather you have a utility or a percise gen set will determine if it shuts off or not not all over voltage and over HZ safeties work on utility units.

 

[flydude92]

It could I would use Electric contact cleaner. You can get it at parts stores. Also depending on weather you have a utility or a percise gen set will determine if it shuts off or not not all over voltage and over HZ safeties work on utility units.

I hadn't heard that before. I have a utility gen set but will check the TM's again to see if it mentions the difference. Thanks.

 

[leedawg]

Pretty sure there is a data plate mentioning this down around the convince outlet...

 

[PeterD]

Would brake cleaner remove the coating on the board?

No, not in my experience. That is a tough coating--when I was in the military we had a hard time getting it off to repair boards. However if you are worried, use some dishwashing detergent in clear water, and a scrub brush.

 

[flydude92]

More updates: It is a little difficult to bench test the components without a variac
so I bought one. (I’m always looking for a reason to buy tools) I tested the
overvoltage relay (K2) and found it is working properly. It turns out the 28V
I thought was used to operate the relay was actually going to ‘NO’ contacts on the
relay assembly. These contacts operate the overvoltage fault light and it is working.
The other set of contacts are ‘NC’ contacts that are supposed to shut down the
generator when a fault occurs. These contacts are also working properly except the
generator doesn’t shut down. I believe relay K1 (stop/run relay) should be shutting
down the generator when a fault occurs.
If anyone can verify that or give me other possibilities please let me know.

I bench tested the control cubicle relay assembly (consisting of relay K1) and it is working.

I also bench tested the exciter/voltage regulator for 3 hours and it tested good. I put it
outside in 30 degree weather overnight and it still tested good. Every box I have opened
in the generator has looked almost new EXCEPT for the exciter/voltage regulator assembly.
This thing has corrosion, rust and dirt all over it. It’s obvious it wasn’t the original assembly.
Someone replaced the original with this piece of junk from a well-worn machine.
I purchased the necessary parts to rebuild the regulator but I am still waiting to finish
checking out the rest of the generator before I work on it. I’m actually considering replacing
the entire regulator assembly with an aftermarket system.

I bench tested the special relay assembly and found a bad relay (K8-fuel level). It seems
the ‘NC’ contacts that should shut down the machine in case of fuel problems won’t open
when power is applied. I have a replacement coming from Delk’s.

Until the next update, enjoy. Brian

 

[flydude92]

I finally found the problem preventing the generator from shutting down when the overvoltage
fault occurred. The Start/Run/Stop switch was wired incorrectly. Either someone miss wired
it by accident when replacing the switch, miss wired it to cover a problem or did it on purpose
to cause problems for someone in the future.

There is a wire that bypasses the fuel level, water temp, oil pressure and over volt fault
switches/relays temporarily while starting the generator. This wire runs thru pins 5 & 6 of the
Start/Run/Stop switch. That portion of the switch is normally open and closes only when it is in
the Start position. On my machine this wire was connected thru pins 8 & 9. These contacts are
normally open and close when in the Run position always bypassing the fault switches. I
included a picture of my switch connected IMPROPERLY in case someone else has the same
problem and doesn’t know it. Just open the control panel and compare switch S2 to the picture.

I ran the generator for 25 minutes with no problems. Even the regulator worked.
I simulated an overvoltage problem to verify the generator will shut down as it should.

If only I can duplicate the overvoltage problem so I will know that it is fixed.

Brian