MEP-831A, No Output Voltage

[sshaw]

Hi guys,
I recently picked up a MEP-831A that had no output voltage. So having had some experience, I checked the output of the inverter, no voltage, pulled the P15 and P16 connectors and checked all of the Generator windings, all had approximately 1 ohm of resistance except the A2-B2 and the C2-b2 winding which was showing .565 mega ohms. I suspect the B2 winding has an issue. The output voltage from the unit showed a low voltage (112V) on the C2-B2 winding all other windings looked ok. I was a little surprised that I had no voltage from the inverter whatsoever. Is this normal even with one bad winding? or do I have an inverter issue on top of the generator winding issue? I haven't pulled the cover off the PMA to get a better look yet. Hoping to maybe find a damaged wire or something obvious. So here comes the questions;
If the winding is damaged, can a motor rewind shop rewind it for a reasonable price? I seen a winding on website for sale for 1400.00 or so dollars, that seemed pretty expensive or am I just out of touch?
Is it possible the voltage selector switch cover door might be defective as I would have thought that I would of gotten something (voltage wise out of the unit). And if I have to replace the windings, its seems like I seen something on the magnets being extremely strong thus requiring extreme care, so I would be open to any words of wisdom you guys are willing to put out.

Thanks a million
Steve

 

[Dewie38]

yes you need all 4 windings for the inverter to work
sounds to me like you have a bad winding in the stator
the stator for sale on the internet is waaayyy to expensive.
that's about what the entire PMA is worth.
the inverter may have a blown input fuse (there are 4 of them) because of the bad winding.
to pull the PMA use a Ford steering wheel puller.

 

[sshaw]

I was afraid of that, just hoping a rewind shop might be able to rewind it at a reasonable rate. Anyone know of a shop that has done a few of these in the past?

Thanks guys, great info.

 

[Dewie38]

one thing you could do is remove the P15 and P16 from inverter, start the set, place the black knob (start/stop knob) on the engine to half way.
the reason for doing this is to keep engine speed slower. slower the engine speed the less voltage out of the PMA.
Take a DMM set to AC volts and measure voltage the same as you measured resistance of the windings.
What ever the readings are they should be close to each other, you are not looking for any certain voltage level just looking for balanced voltage.

 

[Dewie38]

Sorry...I forgot the most important thing,
Be careful measuring any AC voltage on an operating genset.
Holding the P15 and 16 connectors and trying to place meter leads into the connectors to make contact with the pins to get a voltage reading is very tricky.
Be careful or get help holding the connector

 

[Dewie38]

sshaw PM me, I might be able to hook you up

 

[sshaw]

So I did pull the P15 and P16 connectors and measure voltage, everything looked good with the exception of that one winding that had the high resistance readings. It was reading 30-40 volts lower that all the rest. I did pull the end cover off the PMA hoping to find something looking like it was in distress, but everything looked good. I'm going to double check all my findings one more time but suspect I will find them to be the same. I looked at the manual, looks like it time to pull the rotor. (thanks dewie38 on that tip about the ford steering wheel puller, I'm going to the auto parts store to see what I can find). On a practical note, do I need to slide something between the rotor and the stator when I pull that bugger? Sound like at some point it comes free and there is some slop in the fit (between the rotor and the shaft), I'm concerned that the windings can get damaged even more that they are or am I worrying about nothing since its not working now? Thanks for all the feedback, it is truly appreciated.

 

[sshaw]

Hello All,

Thanks for all tips and pointers, looks like I might be making some headway. Well I was pretty sure I had a stator problem and was preparing to for the worst. All indications were pointing to a bad B2 winding which was reading low by 30-40 volts. Dewie 38 suggested looking at the wires at TB6-1,2,&3. Once I starting looking, it was apparent that someone had mis-wired the terminal block. They had either the 5 or 6 wire on TB6-3 position and it was a mess. I was able to correct all of the voltage issues from the PMA, everything is balanced, and the two wires providing voltage to A9 is reading 40 volts. So I now have voltage to the converter but still no output and suspect I'm going to need to pull the converter and open it up to see what is going on inside. Just also wanted to let everyone know that Dewie38 was spot on with guidance, it let me zero in on the issue pretty quickly, so a big thank you. Still have additional work and troubleshooting so I will update as I work through the issues. Thank you.

 

[sshaw]

Hi Guys,

So my voltage issue to the converter has been resolved. This weekend I pulled the converter (A out and removed the cover panels to see what I could find. Much to my surprise, all looked good. Nothing blown out, no faultly caps, no hot spots on any of the boards, everything looked like it was supposed to. The P15, P16 and P17 connectors all appeared to have some black residue with in the connector, (I'm guessing fuel oil) so I cleaned those with some contact cleaner and dried them. I also checked the door switch to ensure it was operating correctly, and reinstalled everything. I started the engine and measured the input voltage (190 ish and even across all phases) and unfortunately no output from the converter and I mean 0 volts. I'm not sure what turns this thing on, but its hard to believe its bad. I don't mind replacing the converter (A if I know for sure its bad, I'm just not convinced its bad. Can anybody recommend some next steps in trying to troubleshoot this unit? I know book says replace it, just want to make sure I don't end up with two converters that aren't working.

Thank you

 

[dav5]

Make sure the fuel level is not low. One of my 831a's loses output when the fuel level is low. The no fuel light doesn't come on and it runs fine but the output stops. I have no idea why this happens. I just make sure to keep it fueled.

 

[DieselAddict]

Do you have the normal 24v DC control power everywhere it is supposed to be? All the gauges working?

 

[dav5]

Yes all gauges work. Since I put a new controller in everything works great. It only had 2 hours on it since reset. I usually fuel it daily when I have a power outage and never run it enough to go through a tank in a day so I never noticed until recently. It isn't a concern but it would be nice to figure it out.
Another thing I have noticed on both units with less than 15 hours after tier 2 reset is that the controllers in both units had not been replaced. The adjusting screws showed a lot of wear and the new controllers have a raised area that isn't on the old ones.

 

[kloppk]

...and the new controllers have a raised area that isn't on the old ones.

I noticed the same thing on my 831A's. Maybe GAC re-designed them at some point.

 

[sshaw]

Thanks DAV5, I will go over everything on the fuel system as I know there are some issues with it. I had a couple of connectors that were apart when I received the unit, so I put them together and promptly blew the FU1 fuse. During this time I also noticed I wasn't getting any voltage out the PMA. I disconnected the two connectors and magically the voltage returned! No sure what is going on, but based on some of the mis-wiring I've found there no telling what they got going. Can anyone tell me what turns this unit (A on and off? Hard to troubleshoot when I don't know how the converter is controlled.

Thank you

 

[Dewie38]

Take the inverter out and check the fuses under the side cover where the connectors are.
The fuses look like little black resistors they are numbered F1-F4, you may have to scrape through some coating to get a resistance reading.
I'm guessing with the mis wires you had from the PMA that you probably have at least one blown fuse.
And yes GAC did re design the controller.

 

[NATCAD]

Maybe also look for leaky capacitors

 

[sshaw]

Guys, thanks for all the responses, they help a lot. So I pulled the inverter and popped the side cover off and started looking. I'm guessing the "black resistor looking items" are right near the connectors P15 and P16? I see (4) black resistor looking items, unfortunately the lettering is under them and I can't make them out. I see (4) at each connector. Also one other question, I noticed a cooling fan on the bottom of the inverter. Is this fan supposed to start and run anytime power is applied to the inverter?

Thank you