Miller MGC-80-1

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Miller MGC-80-1

Postby Preacher » Sat Dec 06, 2008 8:31 am

Howdy, I'm Dave from WV. I'm an HVAC contractor and part-time local pastor. And I have a question.

I went out to service a mobile home furnace, which was a Miller MGC-80-1. And when I got there, it was working fine. Actually I have never been able to catch it acting up yet. So...........

The problem is that the blower kicks on and off during the heating cycle at random intervals. I learned this from the customer and also by hearing it for myself as they held the phone up to the furnace while it was acting up.

When I was there the first time, I cleaned the motor because it was caked with dust from years of not having a filter. I thought maybe the lack of airflow in the vent holes might be causing the motor to overheat and trip the overload. But it still acted up.

Right off the top of my head, 2 conclusions come up, bad motor or bad fan control. Problem is, without being there to check and see if the motor is getting voltage during the down times, it's hard to tell which one by guessing. Like the saying goes, it's hard to fix something when it's working. :)

I came across this site when doing a search for a wiring diagram and figured I'd pick your brain in the process.

So ......... any ideas or suggestions???

Thanks in advance.

ETA: Also, there is no set pattern as to how long the blower runs or how long it's down when it quits.
Preacher
 

RE: Miller MGC-80-1

Postby Robert » Sat Dec 06, 2008 6:55 pm

Hi Dave,

Though it is intermittant with no set standard, does it at least do it once a day or every other day ?


Thanks,
Robert
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Postby Preacher » Sun Dec 07, 2008 6:18 pm

They say that it runs fine initially for 20 minutes and then it starts acting up and will continue to act up until it's shut down for a while. So to answer your question, I'd have to say everyday.

When I first tried to catch it in the act, I waited nearly an hour each time without any flare ups. But recently it's starting to act up more and more. Hopefully I can catch it in the act when I go back tomorrow. Thus far I have been depending on input from the customer, but have found their info accurate so far.

Sounds like it's just a matter of time before it quits altogether. Then it will be easy to find. But the water lines might not be so happy. :)
Preacher
 

RE: Miller MGC-80-1

Postby Robert » Mon Dec 08, 2008 4:38 am

Hi Dave,

Jumper the fan control contacts or straight wire bypassing fan control only.

IF it still does it, it is the motor. IF stops doing it for 2-3 days, it is the fan control.


That's how I would do it if it did not fail while there.


Take care and best wishes,
Robert
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RE: Miller MGC-80-1

Postby Preacher » Tue Dec 09, 2008 7:06 am

Well I actually caught it in the act this time. Motor was receiving juice the whole time while cutting out. Swapped out the motor and it's been running fine ever since.

I was able to find the motor locally. I realize you fellows are in business here, so if I ever need to order any parts in the future, I'll keep this site in mind.

Thanks for the answers.

Dave
Preacher
 

RE: Miller MGC-80-1

Postby Robert » Tue Dec 09, 2008 6:42 pm

Hi Dave,

You're very welcome, happy to help. Thanks for update.


Take care and best wishes,
Robert
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