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xbn268 · Jun 14, 2009, 07:55 PM

The furnace is an older model Carrier. I do not know at this time the exact model. It is at this time about 20 years old.
The central air is a newer Carrier Performance series model. It is two years old.

I have checked to make certain the blower moves freely; it does.

The blower in the furnace works when the heat is turned on. However, when switched to cooling, the blower does not go on. I have repeated going between heating and cooling. Each time the blower will turn on when switched to heat, but will not when switched to cool.

I believe the problem is electrical, either the fan relay or capacitor, but I am uncertain of how to proceed.

Would someone please offer some advice? Thanks, I do appreciate it!

xbn268 · Jun 14, 2009, 08:13 PM

Just to add some information about my system:

The furnace is a gas furnace located in the basement. The blower will turn on as usual about a couple minutes after the system is set by the Honeywell digital thermostat. I can hear the furnace start by turning on the gas and ignition, burning, then the blower comes on.

The central air unit is located outside. When the system is set to cool at the thermostat, I can see the outside system's fan blades rotating as usual. In the basement by the furnace, I can hear some noise, but I am not certain it is anything unusual: it seems to me to be only starting up. However, unlike when in heat mode, the blower does NOT come on after a couple minutes. The blower does not come on at all. The thermostat still says the system is on, also the outside system's fan or rotating as usual. The blower does not come on if I wait.

wmproop · Jun 14, 2009, 09:50 PM

Could be that the high speed of the multi speed motor is bad, high speed is what works in the a/c mode,, in heat mode it runs on slower speed

xbn268 · Jun 14, 2009, 10:40 PM

I have found this thread. Oddly enough, it seems to be the same problem with the same brand - Carrier. Just to add one more bit, in my case as it is in this thread: it does not matter if the fan is set to either AUTO or ON position, it just does not come on in COOLING mode.

https://www.askmehelpdesk.com/heatin...de-219340.html

xbn268 · Jun 16, 2009, 01:35 PM

Can anyone offer some advice here?

Knowing both that the blower is working in heating mode and that the blower does not working in cooling mode (with the fan either in the AUTO or ON position), I believe the problem is at the controller board in the furnace. Is there a way to bypass the controller board such that the blower is controlled by the On/Off switch at the furnace?

hvac1000 · Jun 16, 2009, 02:15 PM

Is there a way to bypass the controller board such that the blower is controlled by the On/Off switch at the furnace?

Not suggested. If you have the meters and know how to use them then test the system properly to find out which part is defective. If this is not done properly you might end up causing more problems which in turn will cost you more $$$.

Sometimes it is easy to say just replace a part and all will be OK but that is not always the truth. Many times on this board we use the educated guess diagnosis syndrome since we are not there to do the proper testing and most home owners have no idea how to do the testing themselves.

If you have a circuit board you might label all the wires and remove. Look on the back side and front side for burnt or overheated areas that might indicate it as defective.

If all else fails you can call for service from the company that installed the A/C since it is 2 years old it is about time to have it serviced anyway.