AC compressor starts and stops, no cold air

  • 4.0L
  • 6 CYL
  • 4WD
  • 132,000 MILES
What can cause the air conditioning pump to intermittently turn on for a few seconds and then go off and then keeps repeating this?

Could this be a relay?
Do you
have the same problem?
Wednesday, June 20th, 2018 AT 8:53 AM

1 Reply

This is the extremely common symptom of low refrigerant. There are some kits to recharge it yourself that are fairly fool-proof, but the only way to know how much refrigerant is in the system is to pump it all out and recover it, then pump in the measured amount called for. Chrysler was the only manufacturer that used a sight glass for this purpose that was accurate. If you have that on your receiver/drier, you can add refrigerant just until you stop seeing vapor bubbles flowing through that sight glass. More is not better. In fact, over-charging the system after the bubbles have disappeared in the sight glass can be more harmful to the system. That can allow liquid refrigerant to slosh into the compressor and destroy it. As a side note, some Ford products use a sight glass too, but you cannot use them. When the system is fully-charged and even over-charged, there will still be bubbles in the sight glass.

Be aware refrigerant is extremely dangerous to work with, so be sure to read the warnings on the can. It can cause blindness and frostbite. Professionals wear gloves, safety glasses, and a face shield.

Here is a link to a dandy page with more information:

If you have trouble getting all of the contents from one can into the system, place the can upright in a pot of hot water. That will cause the refrigerant to boil faster. It must go into the system as a vapor, never as a liquid.
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Wednesday, June 20th, 2018 AT 8:31 PM

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