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I have a Nordyne/Miller Model M1MB 077A BW that the blower has started running today even with the thermostat turned down and also switched to off. The red light is steady on And the yesllow is flashing. The sticker says that means "weak flame". Went back to look again and the yellow light is off. I have placed a call to the "furnace man" and waiting for a call back. Wondering if any one knows what is causing this or how much its going to cost me. Thanks!

Hi,

Was the t-stat set for a/c or heat when it did this ?


Thanks,
Robert

Quick response... thank you. The answer to your question is, neither. It is a sliding type switch with 3 positions, Heat, off and cool. It is in the Off position. Maybe not the best description but hope it helps. Thanks again.

Hi,

IF you have a multi-meter to test voltage, may can solve this quickly.


Go to furnace.


Remove door, open control box and locate control board (red and yellow lights).

ONLY do this IF blower is running non-stop still with t-stat off.


Look on board for CWGR. Set meter for testing 24VAC and place one meter lead on C and the other lead on G.


See what it reads.


Then, locate terminals COOL, HEAT and the 4 NEUTRAL terminals.


Set meter to test for 120VAC:


IF facing the above, place the black meter lead on the 2nd Neutral from the right.


Place red meter lead on COOL, see what it reads.


Then move red lead to HEAT and see what it reads.


Let me know what you find if able to do tests.



Thanks,
Robert

My "furnace man" has just left. He checked circuit boards in furnace and t-stat (among other things) and all checked out to be fine. He said the only thing he can think of to explain it is that there may have been a quick power loss or surge to set it off. I was going to call him anyways to do a service on it before winter so he has done that also while he was here. Cost me $68. I live way out in BFE so it must have cost him that much in gas just to get here and back. If it doesn't happen again then I guess it was worth the cost for the service and knowing its ready for winter. Does this "diagnosis" of the problem sound correct?

Possible. Was it not doing it when he arrived ?


If it was or after truning breaker on/off, continued or did it again, then there is a problem.


If it had stopped or didn't do it again after power was turned off/on, then could have been from a surge possibly.



Anyway, $68 for service call and inspection is fairly cheap.



IF you have a meter, the tests I gave will tell what's up pretty much if it happens again.



Thanks,
Robert

It was doing nothing at all when he arrived. In fact the flashing yellow light had gone back off and it was as if nothing had ever happened. I felt kind of embarrased that I called him out when it was doing nothing at that time and... I am female and again, embarrased to say that I dont even know what the meter is that you recomend to use.

Hi,


Oh ok, don't be embarrassed, it happens, nobody knows all about everything.


Circuit boards act quirky when there is surges and/or power loss sometimes, so maybe all is ok now.



Take care and best wishes,
Robert

Robert, just wanted to say thank you for your help and fast response. You have been very helpful. Glad the problem is solved. Thanks again.

Hi,

You're very welcome, happy to help.



Take care and best wishes,
Robert