Interthem unit main fan sw issue

Questions about repairs and parts for Nordyne furnaces, air conditioners and heat pumps for manufactured homes including Intertherm, Mac and Miller brands. Click here for Nordyne parts.

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homebuff
Posts: 325
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Location: sallisaw, okla. 74955
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Sat Mar 17, 2012 11:57 am

:( I was cleaning the dust off the back of the blower unit fan motor when the relays in the box tried to kick on but I had the main 3 way rocker fan switch in the off position.
Now the switch has no affect on turning it off & on even when the a/c is running.
While the fan was running I tried it in auto & on position bur still stay's running.
It shuts off when I either turn the a/c off at the thermostat or raising the temp.
The switch is practically new.
Wondering if something shorted out in the switch to ground all together.
Humm!! :?:
I am a certified ford diesel tech, "Retired Now" Ford Parts Department counter man, computer consultant, repairman & programmer


DaleM
Posts: 385
Joined: Wed Apr 07, 2010 10:07 am

Tue Mar 20, 2012 8:45 pm

Sounds like it's working right. The relay only powers the fan if there is power there to send to the fan. When the Tstat is on cool and calling for the air to be on the blower will run regardless if the switch is in the AUTO or ON mode. When switched to OFF the blower should stop. If something shorted you would either lose the blower all together or taken out a breaker.

homebuff
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Location: sallisaw, okla. 74955
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Wed Mar 21, 2012 9:24 am

:D Thank's DaleM!
It might have done something cause the blower does stay running when it's in the off position.
Didn't smell anything burning as such though.
Well! At least it stills turns off when I either turn it off at the thermostat or set it to a higher temp to turn off the a/c.
Have to remove the switch to see if it might have burn't out.
I checked the wiring carefully for any wires coming loose or trying to short.
I moved my arm in the area rubbing against the wires at the motor's back section to clean the back side of the motor.
That's when I heard the relay's in the box try to kick the motor on for just a split second.
Going to soon replace the motor with the correct one for it's making a weird very slight dragging, chirping noise. The motor is a non oiling type motor so it can't be oiled.
The motor works fine when the a/c is on but not when I have the heat on in the winter.
The motor is the wrong rpm cause it blows too much air across the heat exchanger allowing the furnace to not heat up enough then shuts back off.
Someone online told me that wouldn't have an effect on it working that way.
I totally disagree!
I had to also remove the burner last winter to clean out the debris from the orifice.
It at least has a good burning flame then which before it didn't.
I believe the cage is slightly rubbing against the housing from being out of alignment.
Hope that's all it is!
Next time i'll kick the breaker instead so this doesn't happen again.
Thank's again for the tips! :D
I am a certified ford diesel tech, "Retired Now" Ford Parts Department counter man, computer consultant, repairman & programmer

homebuff
Posts: 325
Joined: Sun Mar 18, 2007 8:38 am
Location: sallisaw, okla. 74955
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Fri Aug 10, 2012 4:39 am

:) Sorry!
But I don't see what that has anything to do with my issue.
Besides I have no idea what your getting at anyway. :?:
Thank's :wink:
I am a certified ford diesel tech, "Retired Now" Ford Parts Department counter man, computer consultant, repairman & programmer

homebuff
Posts: 325
Joined: Sun Mar 18, 2007 8:38 am
Location: sallisaw, okla. 74955
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Wed Jan 02, 2013 4:03 pm

Just purchased another new AOSmith FDL6002A 3/4 -1/5 hp motor to go into this furnace.
I'm wanting to rewire the motor to slow it down to a 1/3 hp so the heater chamber will stop kicking off so soon once the heat exchanger heats up.
The motor thats in it now is a WhiteOcean 3/4 hp & is blowing too fast to keep the exchanger hot enough throught the heat cycle.
I also found a 626235 Fan and Limit Switch Assembly 3 blade terminal type to purchase from here on MHR site if it will work & is capatible with my MGH furnace.
Looks identical to my old one.
I am a certified ford diesel tech, "Retired Now" Ford Parts Department counter man, computer consultant, repairman & programmer


homebuff
Posts: 325
Joined: Sun Mar 18, 2007 8:38 am
Location: sallisaw, okla. 74955
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Thu Jan 03, 2013 11:04 am

Fighting with the cage to come off the motor shaft & won't budge.
Cage is new & hasn't been on it that long.
Tried wooden block & hammer.
I just gave up.
I am a certified ford diesel tech, "Retired Now" Ford Parts Department counter man, computer consultant, repairman & programmer

homebuff
Posts: 325
Joined: Sun Mar 18, 2007 8:38 am
Location: sallisaw, okla. 74955
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Thu Jan 03, 2013 11:14 am

Any one know how I can test & ohm out the 3" thermal disc fan limit switch after I replace the motor?
Thank's!
Thought maybe the fan being wired to high rpm all the time could be causing the fan to shut off too soon once it cools down too fast & once the echanger has heated up.
The echanger does heat up to the temp it needs then turns the fan on but then when the fan is running too fast it shuts it back down.
Maybe the limit switch is bad & makes it shut down too soon & its a hard one to find for my Intertherm MGH-055-ABWN-06 model central heat & air furnace.
It has a 2 thermal disc type
I am a certified ford diesel tech, "Retired Now" Ford Parts Department counter man, computer consultant, repairman & programmer

homebuff
Posts: 325
Joined: Sun Mar 18, 2007 8:38 am
Location: sallisaw, okla. 74955
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Thu Jan 03, 2013 11:51 pm

I assume sooner or later someone will read this about my progress so I wanted you to knw where i'm at.
My a/c heat repairman friend came out & replaced the motor & left me standing while I found out afetr he left the 24volt gas vale regulator would not kick in but heard the clicking at the non-
programmable Hunter thermostat heat selection but no clicking heard at the valve.
Checked it with my multimeter & no reading if I had it set on the right dila selection at the dvom meter.
Sonewhere in one of my old post robert told me how I could jumpp the 3 way on.off. auto rocker switch & that if i'm not mistaken would be the way to tell if the swtich was bad or not.
It makes the fan come on continuously while in the fan "on" selecton.
Nothing happens in the auto selection.
My a/c tech told me he never touch that part of the wiring while installing the motor.
Did fine the main hot lead inside the relay box cooked though before he found it.
Any ideas anyone?
Thank's! :wink:
Oh! Took forever to get all the air out of the gas lines all the way to the gas valve.
I am a certified ford diesel tech, "Retired Now" Ford Parts Department counter man, computer consultant, repairman & programmer

DaleM
Posts: 385
Joined: Wed Apr 07, 2010 10:07 am

Fri Jan 04, 2013 12:21 am

Post some pics of what you have. The limit switch is a normally closed therm-o-disc. You will read 0 on it. The only time it opens is if the furnace goes into some type of overheat mode, blower motor failing to run will cause a situation like that.

Are you up and running now?

homebuff
Posts: 325
Joined: Sun Mar 18, 2007 8:38 am
Location: sallisaw, okla. 74955
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Fri Jan 04, 2013 12:39 am

Thank's Dale!
I will get back tommorrow with then pics if they will upload to here.
I always have the problem geting pics accepted from the wrong format size.
I was trying to remember what Robert asked me to do by jumping two of the 3 wires to see if the fan comes on & the Gas valve clicks.
My a/c heat guy said he would be out in the morning around nine.
Just trying to see if I can figure it out to night cause its suppost to get down in the 20's.
LIke to know what setting to put the dvom on the test the circuit at the gas valve for 24vac & how to probe the two terminals on top of the valve & see if that 3way roker switch might be the problem with no heat.
The piot light did finally light after getting all the air out of the lines.
I'm tired so i'm going to bed & hope to resad a reply back from you or Robert Friday morning maybe before my a/c tech shows up at nine.
Thank's! :wink:
I am a certified ford diesel tech, "Retired Now" Ford Parts Department counter man, computer consultant, repairman & programmer

homebuff
Posts: 325
Joined: Sun Mar 18, 2007 8:38 am
Location: sallisaw, okla. 74955
Contact:

Fri Jan 04, 2013 11:38 am

:D He came out this morning & found some wiring behind the thermostat loose on the RH lead.
Heat working fine now.
Still want to replace that high & low 3" dual thermal disc limit switch soon when I can find the one that matches the one in my unit.
Thank's for your help.
Still have to figure out the pic upload problem to here.
I am a certified ford diesel tech, "Retired Now" Ford Parts Department counter man, computer consultant, repairman & programmer

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