I just turned on the AC for the first time this season and I noticed that the condenser fan outdoors is continuously turning on and off intermittently, i.e.. on for three seconds, off for three seconds; on for three seconds, off for three seconds, etc. This is a Carrier unit. Any idea on how I can repair myself or should I put up a service call?

Not an easy solution from where I sit. It is a very unusual problem and might need some trained eyes at the unit to figure it out.
Good Luck

Is the compressor shutting off as well? Or just the cond. Fan?

The fan on the compressor outdoors is all that I am noticing that is shutting off.

Well it could be that maybe it is going out on overload, but it would stay off longer. There isn't any type of fan cycling device on the unit? Does it act like it has any trouble starting back up? Is this the first time that you have heard this system run? If so it sounds to me like it has a low ambient control on it, therefore that is normal...

This is the first time that this has occurred. I've had the system for seven years and never had this problem. There is no indication that it has trouble starting back up. I have a service technician from the hvac company that originally installed the system coming on Monday afternoon. I'll let you know what he/she comes up with. Thank you for your help.

Is it a R22 or R410 refrigerant system? Top of the unit above the freon lines is a rating plate.It will tell you how much and what type of refrigerant you have(out side unit). The R410A unit has a pressure switch that will cycle the condenser fan motor it may be going bad or low on refrigerant will also do it. Give us more info if you can.

It is a R410A system. The hvac technician said that it had a valve stem leak which caused it to be low on refrigerant, which caused the low pressure control switch to make the fan run intermittently. All set now. Thank you all for your help.

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Originally Posted by racednav

It is a R410A system. The hvac technician said that it had a valve stem leak which caused it to be low on refrigerant, which caused the low pressure control switch to make the fan run intermittently. All set now. Thank you all for your help.

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Most A/C's use the low pressure switch to open the low voltage on the contactor, so when it tripped on low pressure the entire unit shut down, not just the fan. I realize most homeowners don't quite understand fan from compressor, but that would be very useful information for us online to know. I'm simply putting this post here in hopes that others with similar problems will read it.

Carrier\Bryant has a vapor pressure switch that cycles the condenser fan motor. They also have the low pressure and high pressure switch that are in the low voltage side to open the contactor.

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Originally Posted by racednav

I just turned on the AC for the first time this season and I noticed that the condenser fan outdoors is continuously turning on and off intermittently, ie., on for three seconds, off for three seconds; on for three seconds, off for three seconds, etc. This is a Carrier unit. Any idea on how I can repair myself or should I put up a service call?

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You want to turn that unit off and not use it until fixed ,can cause major problems to unit ,although that problem is not hard to fix will get back to you in a bit with what it is. Let me look in notes

Carrier air cooled unit

Condenser fan runs fine and then goes off when compressors kick in

Can't get both to run together

Off course compressors will also stop on thermal shutoff I guess

Any ideas what's up

Changed freon filters both compressors c 164 s

Freon cked again after 164 installed today

Thanks
Rob
[email protected]

My Carrier technician bypassed the thermostat and saw that there was 120VAC going to the fan motor and also saw that 24VDC was present at the motor and it still kicked off even though it was still calling for the 24VDC and the voltage was still present. He said the fan motor has a circuit board built into it so the circuit board was bad and he needs to replace the motor. Seems like a silly design to not have the circuit board separate from the motor, but at least mine is under warranty. Hope that helps others who may have the same issue. Measure the voltage going into the Molex connector near the top of the blower and see if the 24VDC is still there when the fan stops blowing... if it's still there then the circuit board built into the fan is the problem.