Air Condition compressor won't turn on

[unibrook]

2001 Forester 99.5k miles:

New condensor and recharge about 1 year ago.

 

When I turn on the A/C switch and fan........no compressor engagement.

 

What are the usual suspects I should check first?

[OB99W]

One of the most common reasons for lack of compressor clutch engagement is that the pressure switch isn't closed due to the refrigerant charge being insufficient. If there's a leak, a year is plenty of time for the charge to have been lost.

[Rooster2]

One of the most common reasons for lack of compressor clutch engagement is that the pressure switch isn't closed due to the refrigerant charge being insufficient. If there's a leak, a year is plenty of time for the charge to have been lost.

 

My same thoughts, the system is low on 134 refrigerant. If you are mechanically handy, and like to work on cars, and have some time, I can give you some ideas on working on the system, that doesn't require much work.

[Fairtax4me]

x3 on the low refridgerant. You can get one of those recharge kits they sell at advance for like $20 and fill it up, but it will probably keep leaking.

[Scoobywagon]

Low refrigerant is the most common cause. This can be tested using a manifold guage set. A word of warning here...the little cheap sets that come in the AC kits a Schucks/Autozone/Etc. are NOT sufficient. You don't have to buy the nice Snap-On or Matco guage sets, but the little plastic ones are not ok. If you have a digital multi-meter, though, you can do some testing and narrow it down before you take it to a shop.

 

Turn the key to the on position and turn on the AC. Ground your meter directly to the battery. Check both terminals on the low pressure switch connector. You should find power on at least one side. Check both terminals on the Compressor connector. Again, you should find power on one pin. If not, disconnect the low pressure switch connector and jumper the two pins. Check for voltage at the compressor again. If you find voltage this time, then either the low pressure switch is bad or the system has leaked down.

[unibrook]

Thanks guys, I will try the multimeter test this weekend.

[OB99W]

It's easy to test if the pressure switch is open or closed, and can be done with the ignition switch turned off. The switch is located at the top of the receiver/drier. According to the manual, the wires at the connector should be green/orange and brown/yellow. Remove the connection, and check continuity of the switch (should be very close to zero ohms) -- if there's no continuity, it's likely the pressure is too low due to refrigerant loss. (A defective switch could also lack continuity, but that's not nearly as likely as low refrigerant. Also, the switch is a dual-action type, and will open if the pressure is too high -- really unlikely, especially on a system that's not running.)

[ferret]

Something else to consider in this thread:

 

http://www.ultimatesubaru.org/forum/showthread.php?t=102171&page=2

[OB99W]

Something else to consider in this thread:

 

http://www.ultimatesubaru.org/forum/showthread.php?t=102171&page=2

That's good info, and should be checked if the pressure switch is found to be closed.