Troubleshooting a Condenser Fan That Will Not Turn Off

It has been one of the hottest summers with never ending 95+ degree days forcing my central air conditioning unit to work overtime. Although my unit is over 16+ years old, I have maintained it regularly so it is still in good working condition.

But one night, my son woke me up at 3am to complain that his room was freezing. True enough, his room thermometer indicated 71 degrees, which is much too cold while sleeping. So I trudged downstairs and checked on my Honeywell thermostat.

Maybe because I was still groggy, but I was confused as to why the air conditioner was running (I could hear both furnace blower and condenser fans running) when my thermostat was set to 76 degrees and the current room temperature was showing up as 71 degrees.

Thinking my thermostat was confused, I overrode the setting controls and turned off the air conditioner from the thermostat. But that action turned off only the blower fan and I could still hear the condenser fan running so I manually tripped the corresponding circuit breaker (dedicated to my heating and cooling system) and went back to bed.

Next morning, I switched on the circuit breaker again and hearing nothing, turned on my AC from the thermostat. It seemed to work fine all day but at the end of the day, the condenser fan had a mind of its own so cut the power off to the entire AC system again.

I called several HVAC places and they all wanted $300+ just to come out and take a look. For that kind of money, I thought I’d try to troubleshoot myself first.

REQUIRED PARTS / TOOLS

• Socket + Ratchet
• Can of compressed air (I use Dust-Off Compressed Gas Duster – 4 Pack – DPSXL4)
• Plastic coffee stirrer (get some at 7-Eleven or QuikcChek) in case your air can nozzle breaks off
• Pancake Compressor

ALLTHUMBS DIY – WHAT I DID

Based on the fact that my thermostat was able to control the blower fan, I guessed the problem was caused either by tan HVAC controller unit (located in the blower fan unit) or from s failed component inside the condenser.

If you are interested in learning about HVAC condenser component names, Inspectapedia.com has an excellent article.

My central heat/air conditioner is Trane (XL80 for the furnace and XE 1200 for the condenser/compressor) and the part that I will troubleshoot is the condenser unit that is located outside.

Step 1 – Turned off the circuit breaker at the main panel

Step 2– Removed the quick disconnect connector

Step 3 – Removed the access panel on the condenser unit

Step 4 – Removed the cover panel inside the condenser unit

Step 5 – Take a can of compressed air and blow out all debris. Most air cans come with a skinny but sturdy plastic nozzle that can get into small crevices. DO NOT USE compressed air from a a pancake compressor as the air from it is TOO strong.

Step 6 – Make sure to blow out dust and other particles between contactor plates by using the plastic nozzle because a contactor’s CLOSED or OPEN position turns on or off the condenser.

Step 7 – While the panel is removed, check the metal cooling fins and remove large debris as well as any accumulated dirt on the bottom. I used my Porter Cable pancake compressor for this purpose.

CONCLUSIONS

Most times when I am troubleshooting, I get very frustrated because it’s like opening a can of worms. But this time, I got lucky because simple cleaning solved my problem.

I will be posting a follow up article when I replace the contactor and two capacitors soon.

Well that’s it for this part of the article. I hope it helped you at least a little bit in solving your Trane condenser/compressor problem.

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Thanks and good luck!

REFERENCE LINKS

• How Stuff Works – Heating and Cooling
• DIYHVACrepair – Contactor
• DoItYourself – Contactor Niot Engaging
• House Repair Talk – Condenser Fan