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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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The blower runs but the compressor does not come on to supply

Customer Question

the blower runs but the compressor does not come on to supply refrigerated air. an electircian checked the fuses and they have not blown. The Honeywell thermstat seems
to be functioning. Are there filters on the compressor or AD unit that are precluding the
compressor from coming on?
Submitted: 2 years ago.
Category: HVAC
Expert:  Tim H. replied 2 years ago.
Hi, I'm Tim and I'm an HVAC expert here to assist you with your questions. Please provide all information I request as it makes it more difficult to troubleshoot something when I'm not there onsite. Essentially, you become my eyes and ears. Thanks for the opportunity to help. At the end of our dialog, you will have a chance to rate my service, but please wait until we are finished and you're satisfied you have all the information you need.I'm sorry to hear about your issues. I assume when you say "compressor" you mean the outside unit is not coming on? What fuses did the electrician check? Did the electrician measure voltage at the contactor outside in the outside unit?
Customer: replied 2 years ago.
The electrician checked the fuse(s) on the outside of the line into the outside unit and reports that they are not blown and
that there is electricity to the unit.
Expert:  Tim H. replied 2 years ago.
OK, well your thermostat (when you call for cooling) sends 24 volts to the "Y" terminal at the furnace board and then this in turn sends 24 volts out to contactor at outside unit. So things it could be is 1) a bad thermostat, 2) A bad contactor, or 3) it's possible it's locked out on a pressure switch. To determine which of these, we would need to take some voltage readings. Is electrician still there or do you have access to a voltmeter?
Customer: replied 2 years ago.
I don't have a volt meter . The electrician will be there at noon tomorrow.
Expert:  Tim H. replied 2 years ago.
We know the outside unit has power, according to what you've told me. So next step would be to check for power to the "contactor" at the outside unit with cooling called for. There are spring loaded contacts that should "pull down" and energize unit when cooling is called for. Once I know this information, then I can narrow down the possibilities.
Expert:  Tim H. replied 2 years ago.
Keep me posted on what the electrician finds, please, and we can go from there.
Customer: replied 2 years ago.
Thank you Tim, Sorry for my distraction. Will report after the electrician checks that out. Monte
Expert:  Tim H. replied 2 years ago.
OK, thanks, Monte