Reasons an Air Conditioner Compressor Will Not Start

By | April 5, 2017

Reasons an Air Conditioner Compressor Will Not Start

An air conditioning compressor is the heart of the the unit and can be a real problem if not working.
There are many things that can cause a compressor to stop working.
Below is a list of some common issues to look for when troubleshooting a unit.

Five Reasons an Air Conditioner Compressor Will Not Start

  1. Capacitor
  2. A bad capacitor will not start a compressor and will need to be replaced if bad.
    Testing the capacitor is easy enough with a HVAC multi meter. They are also low cost parts to replace.

  3. Condensing Fan Motor Failure
  4. A bad condensing fan motor will stop a compressor from working. This can be tied to a bad capacitor since Start Run capacitors are often in the same package.
    When the Fan motor goes bad the compressor will kick on for a short while then stop when the Head Pressure builds up.
    Since the heat is not dissipated away from the unit the Amps and heat will build up making the compressor overload and trip off.
    If a unit is left On the compressor will cool down and kick back On, going into a bad cycle of running for a short while, over heating and kicking off. Often an Air Conditioner becomes loud when this happens.
    This could potentiality damage the compressor since the pressures can get high and pull a lot of Amps.

  5. Contacts
  6. The Contacts control the main high 220 volts coming into a unit.
    It uses a low voltage contactors relay to control the high voltage which can go bad and not allow any voltage though.
    Common problem include pitting or the relay coil winding itself going bad.

  7. Electrical Short
  8. If the winding on the Compressor goes bad it will cause the unit to ground out.
    The breaker will throw when this happens. It can happen for many reasons such as a small bug got into the unit and the compressor wiring or simply age.

  9. Float Controls
  10. All A/C units need to drain water when it is humid. If the drain pans or hoses become backed up float controls can turn a unit off.

The above are a few of the main problem a unit can have.
It can of course simply have a mechanical failure and stop working. If you have run into problems let us know in the comments below.



3 thoughts on “Reasons an Air Conditioner Compressor Will Not Start

  1. James L Cue

    I am having problems with my AC compressor not coming on. I changed the 2 fuses out, checked the power to the fuse box (got power to the AC), and cleaned off the fins (LOTS of cottonwood seeds!). I hear it click but the fan does not come on. Am I missing something?

  2. Erick

    Questions? If a condensing coils is dirty how will it affect the operation of unit? And if an evaporating coils is dirty how will affect the operation unit. Can you please helping me with this two questions

  3. shuaibu abdu

    My 2 HP remote controlled window unit’s when plucked plucked to power will not start. The fan starts and run speed controlled normal by remote control but when mode is changed to cooling , the compressor will not start. The compressor however run briefly when connected to the power directly. What should I do.


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