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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22541
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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My blower motor wont turn on at all and we have a new thermostat,

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My blower motor wont turn on at all and we have a new thermostat, the outside is freezing up, and then we got a new capasitor and now looking for a relay switch we cant find

The number you supplied is for the ac coil you have the model number of the furnace/blower unit?

Customer: replied 4 years ago.

GMS90453BXA not sure if the O is O or 0 ( letter or number) but that is on the tag inside the unit on the left side so this is hopefully correct now


Thank you,

and did blower work before thermostat change?

Customer: replied 4 years ago.

Yes, we had turned off the unti since the we saw that it was outside where the unit was frosted up so then the fan would continue to run with the controls on auto and off which made my grandpa think it was the thermostat then the blower motor would come on and off on and off and you would hear a clicking noise on the furnance. So, we then thought it was the capacitor. Also, want to mention that i was at work and my wife was home claimed that grandpa changed a fuse in the unit and that there is two fuses, I can only find one which she claijms is not the one grandpa changed. The one I found is good though but the one she claims was changed i cant find

First lets verify some basics..

If the outdoor unit runs then we know fuses are ok for indoor unit. there a green wire on G terminal?

On the circuit there a black wire from the blower motor to COOL H terminal?

Customer: replied 4 years ago.

Both answers are yes do you mind a hands on test in the furnace at the circuit board?

We need a jumper, short wire or paper clip...if you are willing...

Customer: replied 4 years ago.

I have a paper clip and am listening to do whatever you tell me to

Turn thermostat to off
Turn fan switch at thermostat to "auto"

Remove furnace doors and tape the blower door switch down that pops out...tape it down good.

Locate terminals R and G on the circuit board where the thermostat wires attach.

Turn power on to furnace.

Use the jupmer to short R to other terminals..just R connected to G and hold.

Tell me if click, motor starts etc...

Take your time as I will be not hurry

Customer: replied 4 years ago.

THsi new therm is digital and has no switch to turn turn it on auto digitally it turns cool on, which is since this one has no switch to click on auto.....however, I did go try the test to the R and G on the circuit board and nothing is happening....just worried I have not done right w the termostat


The test we did bypasses the thermostat.

Can you now do this same test but short R to W?

Then tell me if furnace begins to start (heat) only need to hold jumper R to W long enough to see if the draft motor in top section starts

Customer: replied 4 years ago.

Nothing happening

Is the door safety switch still taped down?

Is the purple auto fuse in corner of board ok?

Customer: replied 4 years ago.

Purple fuse is good and my wife is holding the switch in when i ask her to

at this point does the outdoor unit still run if you short R to Y

Customer: replied 4 years ago.

Yes, immediately in summary at this point:

R to Y does turn on outdoor unit
R to G does NOT turn on fan
R to W does NOT tern on heat

Is this correct?

Then we go to next step...and I thank you for your patience

Customer: replied 4 years ago.

thats correct

Now we are going to see if the blower motor is ok or not.

On the circuit board...coming from the door switch you press is a black wire that attaches to terminal "Line H".

Then we have a black wire that runs from the blower motor that is attached to COOL H.

We want to take these 2 wires and connect them metal to can use a small nail inserted into the end of each wire and then put a loose piece of tape over it.

Then press button in and tell me if blower motor starts

Customer: replied 4 years ago.

THis did kick the blower motor on! yeah! So.....???

This means it is the circuit board that is causing you fits. First we bypassed the thermostat...then we bypassed the circuit board.

So your issue is not with the motor itself it is with what turns it off and on.

There is a way to get cooling with constant fan if you wish...this could get you by until board is installed


Customer: replied 4 years ago.

so just leave the wires cool h n line h connected

Actually we need those 2 connected AND plugged onto Line H.

Generally you cut the Line H wire and take the 2 ends and the black motor wire and wire nut together.

So we have a "Y" with the black wire from motor and black power wire combined and then plugged onto LINE H.

Just as a quick test....move the black motor wire from COOL H to EAC terminal...then turn the system on and see if the blower works....this is an accessory terminal for an electric air cleaner...

Customer: replied 4 years ago.

cool h to eac doesnt work

Thank you...that means the entire blower relay side is down.

To get temp cooling you would need to splice the black motor wire into the Line H wire.

I hope all works out for you


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