AC no longer working
 

Hi all,

The AC in my 2007 volvo xc90 used to kick off very cool air. Yesterday I noticed it's blowing out warm air now all of a sudden. The temperature has gotten significantly hotter the last week or so (upper 80s/90s), however last summer I had no issue.

I've looked up things on the refrigerant, compressor, etc. and I'm wondering is there anyway or any tests I can do to eliminate some of these options to try to pin-point it further? I don't have the ability/tools to fix on my own so I will probably have to take to a shop unless there's a relatively simple fix. I just want to avoid being taken advantage of as a young female going in the shop an appearing "clueless".

Thank you!

a professional shop will need to do some diagnostics. First they will check things like relays and fuses to make sure the control signals are telling the compressor to kick on. They may also do a computer scan for fault codes (things like the AC and REC lights flashing are signs the climate control computer has sensed a fault). The will then check to make sure the system is fully charged by putting a pressure gauge on it and trying to force the compressor to kick on. If the pressure is low, they can do a simple recharge and hope for the best or they will inject a dye to see where there may be a system leak. If the pressure is good and the AC kicks on temporarily it may be a worn clutch or may be a failed compressor. Most shops won't bother replacing the AC's clutch or even reshimming it - they will simply replace the compressor and get a new clutch as part of the deal.

You can try doing your own AC recharge so to test for whether you have low pressure in the system, you can try jumpering the lower pressure sensor to see if that will kick on the compressor (its on the return line between the firewall and the compressor - usually over on the passenger side of the engine bay). To do this quick test, start the car, turn on the AC to full cold then pop off the connector and use something like a paper clip to jumper the two leads. If the compressor kicks on, your system pressure is low and you need to add refridgerant. Don't run it more than a few seconds this way. If that works then you can try using a kit with a pressure guage to measure the system pressure off the low side port and then see if you can/should add some refridgerant. If you read zero pressure or can't get the compressor to kick on, its time to call a pro.

Note that adding refridgerant to get the system going is likely to be a temporary fix. If you are low on refridgerant, its a sign you have a leak already so its just a matter of time for the new stuff to leak out as well. Then you'll need a shop to do the dye test and find what's leaking and repair that then professionally service the system.

One good thing to ask is if the shop has an evacuation machine. They withdraw everything from your system.

It catches, filters, measures and recycles both the PAG oil (a "carrier" fluid) and refrigerant.

The one my buddy had (A Snap-On product) would pull on the system for minutes thereafter in order to detect leaks.
Then, if none were found, it would add the correct amount of both PAG oil and refrigerant to which UV dye was added.

You'd pay a service charge PLUS what had to be made up. People would commonly leave after paying the $60 and no additional.