Testing AC in cold weather?

[Elkins45]

I've been test driving used cars and one of the things I (obviously) would like is for the AC to be functional. Unfortunately the highs have been in the teens here so I'm not quite sure how to check for good air conditioner performance. When it's 17º it's difficult to feel a temperature change when you push the AC button.

Maybe breathe really heavy and fog up the windshield, then turn on the defroster? How do dealers check it when evaluating trades in the cold?

 

[dishdude]

The compressor won't kick on if the temperature is below 38.

 

[Kurtatron]

You will need to get the car to operating temp, driving for 10 minutes or so to get the engine bay up - Might take longer with those outdoor temps. Once it’s up to temp, get it nice and toasty in the cabin and set the airflow to recirculating. Now turn the ac on and see if cold air comes out. With recirculating on, the cold air will only be from the evaporator, not from outside ambient temp. If it doesn’t get cold, AC is busted.

 

[KrisZ]

The compressor won't kick on if the temperature is below 38.

That is not true. The compressor will kick on well below the freezing temps, but the engine and the whole system must be heat soaked. That won't happen during a short test drive.

My advice, wait for warmer temperatures.

 

[Jetronic]

there's 2 sensors that stop the AC kicking in... the outside temp sensor and the frost sensor on the evaporator.

get the car warm, on recirc and heat the outside temp sensor. That will get the AC going. If the temp sensor is accessible, like in an outside mirror it's easy, if behind the bumper, less so

 

[zzyzzx]

Testing AC in cold weather?​

You really can't.

 

[Chris142]

You can't properly check AC if it's very cold out. If I don't have charging specs I won't charge a car by pressure if it's under 80'f. Can't get accurate readings below that temp.

 

[Marcozi]

It's a good idea to run the AC in cold weather as this redistributes the compressor oil and exercises the compressor shaft seals. Wait until the engine is warm and then run the AC for 30 seconds.

 

[tcp71]

Every modern vehicle HVAC system will run the compressor with the full defrost setting to dry the air being blown onto the windshield. Turn it to max defrost, go outside, pop the hood and see that the compressor is cycling on/off.

 

[SHOZ]

Every modern vehicle HVAC system will run the compressor with the full defrost setting to dry the air being blown onto the windshield. Turn it to max defrost, go outside, pop the hood and see that the compressor is cycling on/off.

But the compressor seldom cycles when it's really cold. I think it's a timing logic thing at those temps.

 

[andrew_j]

You can’t . Purchased car in cool temps and AC kicking on but summer hit and Barely cold. Thankfully just low on charge after 10 years normal loss. A pro added appropriate stuff for $75 and freezer cold again.

 

[demarpaint]

You can't properly check AC if it's very cold out. If I don't have charging specs I won't charge a car by pressure if it's under 80'f. Can't get accurate readings below that temp.

+1 I'd wait to test the AC when it gets warm again.