MEP 004 main contactor ?

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1942 Mk1

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I am having problems with my MEP004, the main contactor will not pull in to supply power out. The coil tests good, and is receiving power from the switch that energizes it when shifted to the on position. I am finding 35.6 volts present at the energize position at the switch and at the coil.
My question is, what is the working voltage for this coil?
Thanks,
 

Guyfang

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24 volts DC is the normal working voltage. How did you check the coil? 35 volts is rather high. How did you check that at the coil? When you apply voltage to the contactor, do you hear/feel the contactor close. Not that, that is a 100% sign that it works. But it at least means the plunger is free.
 

1942 Mk1

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We checked for power at the Ckt Bkr switch and found voltage, checked for voltage with the switch in "closed" position, then checked for voltage at the connector, between pins, at the contactor block. Found the same voltage at the between pins as we found at the switch.

We took an ohms reading between pins at the block, results were 7.3 ohms I believe. Results were comparable to the ohms reading testing the coil on our Mep 005, but we don't really know if that coil is good as we have not been able to get the 005 to produce power. The 004 makes power, just have to bypass the contactor to get it.

Brother is much more electrician than I am, he took the ohms and voltage readings. As soon as he gets back we can try 24 volts at the pins to check for the click. When I got this generator, it did not run. I had the injection pump overhauled by a diesel service company, I reinstalled the pump and got the engine running. After learning the proper starting sequence it produced power. At that time the contactor would pull in and power was available. Last sugaring season, the governor gave trouble in the generator we were using to power the sugarhouse so we hooked the 004 up and the contactor wouldn't pull in so we bypassed it and ran the rest of the season as such. Ran it probably 200 hours on the meter.

My apologies for the long-winded explanation.
So now it's off season and we thought maybe we could get back on this issue and get it figured out.
Thanks for the quick response.
 

Guyfang

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By "bypassing" the contactor, do you mean you jumped the close circuit? Or simply moved the cables from the input side to the output side? The contactor in the 005, is the same as the 004's contactor. I always found it simpler to remove the contactor, then test it on the work bench. It's not all that much work to pull it out. Then apply voltage to the pins like you mentioned. The use an ohm meter to mesure continuity between the input and output terminals. Do you guys have the TM's.
 

1942 Mk1

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Bypassing, we moved the cables

Upon closer inspection, I found that the mechanical portion of this switch is in fact stuck.......stuck so much I couldn't even pry the switchbox apart. I put the contactor in from the 005 and all works as intended.

Thanks much for your help.
 

Guyfang

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That's what I thought you would find. Open it up. Might be able to fix it. The contacters often fill up with moisture. Then they rust up. Its worth a try, I have fixed many of them.
 
Last edited:

1942 Mk1

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Location
Corinth, Vermont
I took out the screws that hold it together, could not pry it apart. Something is holding it fast from within. Before I broke the case, I set it aside and tried the other contactor and found it to solve the problem.

I found a replacement on the auction block for a price within my budget and have it on the way. I may at a later date find out what has the contactor box stuck so tight.
 
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