Outdoor unit won't come on:

This is a very common problem, whether it is an air conditioner or a heat pump. Unfortunately, many times the service technician is dispatched only to find a simple problem that the homeowner could have fixed himself.

Below is a list of possible causes.

Faulty thermostat
Faulty contactor
Faulty time- delay relay
faulty thermostat cable
Off on a safety device- (low pressure, low temp, high pressure, high temp...)
Faulty control module
Thermostat not set properly
Emergency or shut-off switch turned off
Blown fuse in panel box
Circuit breaker tripped or off- (sometimes a breaker will trip but it won't move)
Outdoor disconnect turned off- (some have an internal pull-out plug)
Condensate pump safety switch opened- (check pump, usually located near indoor unit)
Off on outdoor reset button
Unit "locked-out"- (reset by turning off then turning back on)

Here is a checklist to go through before making a service call:

  • Make sure there is a call from the thermostat
  • Make sure no Emergency switches are turned off (including the furnace switch)
  • Make sure the breakers for the indoor and outdoor equipment are in the "on" position- reset if necessary
  • Make sure the outdoor disconnect is on- some have internal fuses or circuit breakers- if you know how to check fuses you may do so
  • If you have a condensate pump with a safety switch, check to see if the pump is completely full of water- If so, make sure pump is plugged-in and hose isn't clogged (could be a bad pump)
  • If your outdoor unit has a "Reset Button" press it- if that was the problem and you have to press it a second time, there is a problem and a service call will be needed
  • Your unit could have a safety device locking it out. Reset it by turning system off at thermostat or breaker, wait 1 minute and turn back on. Wait up to 10 minutes to see if outdoor unit starts