Furnace blower shuts off when A/C starts

[swampdonkey70]

First-time poster here... I have a 10-year-old Goodmans air 2-ton air conditioner and a 2-year-old furnace. I keep my furnace blower running all the time to circulate air through the house to help filter the air for my daughter's asthma.  When I turn on the air conditioning, the compressor/fan both start on the unit and will stay running with no problem.  It's the blower motor on the furnace that's the problem.  It shuts down as soon as the A/C starts.  It's not a problem at all when heating, only cooling.  I change the filter very often so that's not the problem, and I can't see any corroded or loose wires/terminals anywhere.  I had a service tech look at this at the end of last summer and at first he said it was the filter (I objected), then his next answer was that the unit needed to be replaced because it uses an older refrigerant and if he needs to charge it he won't be able to.  Any suggestions before I'm stuck paying $3K to replace it?  Thanks...

[Admin]

I'm not sure why the type of refrigerant would affect the fan motor unless you have an air handler where the coil is built-in.

Are you saying the air conditioner outside continues to run but the fan motor inside stops and does not restart?

Maybe the high-speed winding in the fan motor or the relay on the control board is bad.  I would wire the high speed fan to continuous power to see if it works and if it does just leave it that way since you like running the fan continuously.

Likely the continuous speed is the same as the heating speed and lower than the cooling speed.

If the high-speed winding is bad in the motor than you can likely get away with the next faster speed if it still works.

Regardless you should be able to replace the control board or fan motor without having to replace the entire system.

[swampdonkey70]

that's correct - the air conditioner outside continues to run but the fan motor inside stops and does not restart (so long as the a/c is running).  I believe that there is only one speed on this furnace.  My thermostat does not have other options and it has only ever run at this speed.  I just picked up a basic Honeywell thermostat and will replace the Nest that's on it now.  If that doesn't work, I'll try your suggestion to wire the fan to continuous power - thanks!!

[Admin]

Usually the user has no control over the fan speeds and that's something that needs to be set inside the furnace.

Do you know what model of furnace or air handler you have?

[Porcupinepuffer]

that's correct - the air conditioner outside continues to run but the fan motor inside stops and does not restart (so long as the a/c is running).  I believe that there is only one speed on this furnace.

You're probably mistaking one speed with 1 stage of heating. The furnace blower will have, at least, 4 or 5 speeds for different installation scenario's... If what you described is accurate, you definitely need a different service tech to look at it. Blaming the A/C for being low on refrigerant has nothing to do with the furnace unless you have a high tech communicating furnace/air conditioning combo, which I doubt since you stated you have a basic stat.

[swampdonkey70]

The furnace is a York Furnace Model TG9S080B12MP11A, and the air conditioner is a Goodman Model CKL24-1H.
I replaced the Nest thermostat with a basic Honeywell model - same outcome.
The light on the control board on the furnace is a "slow green", meaning normal operation.  This is regardless of if the blower is circulating and the A/C is off, or if the A/C is on and the blower won't turn on.  I was hoping to see a fault code that would point me in the right direction but no luck.
I'm about given up.  I think I'll try a different Tech this week.
Thanks for the help.

 

[Sergroum]

Anyone taking bets?


I'm thinking the blower fan wire for his hi cool is off.

[swampdonkey70]

The puzzling part may be that it was working fine, then stopped.  No wiring was ever touched.

[samihabib]

If the t stat turns the fan on independently or during heating but doesn't during cooling means you have an issue with the circuit board , because if you were to jumpe Y and R on the board , AC should turn on and along the fan , the circuit board is not powering the blower motor.

[swampdonkey70]

Thank you samihabib.  I appreciate the guidance.

[Sergroum]

Do we have an update to this? Was the wire pulled off the 'cool' terminal?

[Hvacpimp]

I'm going with the board as well