a/c compressor problem?
 

hi all, i'm new to the volvo fraternity-1997 850 AWD canadian model. being such, i'm learning and reading lots on my new(old!) car.
since winter is FINALLY over and summer is approaching i thought i'd try the a/c out. it was cool that day and i couldn't really tell if it was working.
now something strange is happening : with the a/c switch on auto,regardless of the heater setting, there is and audible click(like the a/c compressor coming on) and a short hesitation from the engine. this process repeats itself approx. every five seconds until i switch the a/c toggle to the off position.after that every thing seems fine.
i didn't have this problem in the winter as i never tried the a/c out. got a feeling the compressor is somehow cycling on and off(hence the slight drop in power when i hear the click). anyone hear of anything similar?
really like the forum and am looking forward to many useful visits

-breton-

RE: a/c compressor problem?
 

You could be low on Freon I would have the level checked.

I know this is an old thread, but I am having the same problem with my "96 850 GLT. When the AC switch is "On", even without the blower on, the engine has a slight hesitation. But once I switch it off, the problem goes away.

Any ideas?

Yep, sounds like you are low on freon. The AC has a couple of sensors that will trip off the compressor to prevent damage. The high pressure sensor is down on the bottom on the condensor (haven't really looked but this is where its on other models) and the low pressure sensor is on the return tube up by the firewall. Trace the return line from the compressor back to the firewall and you'll see a metal pipe with a sensor/connector. To do a quick test, start the car up and turn on the AC to full chill. You should be able to see the AC clutch engage/disengage. Now remove the connector to the sensor and jumper the two leads (I've used a paper clip to do this). restart the car. If the AC compressor clutch stays on, you have low pressure. (don't run this way for more than a minute since the freon also lubes). A second option is to to use a pressure gauge which comes on the better refill kits. If you have low pressure you will need to jumper the sensor to get the AC to kick on to pull in the fill from the can (also remember to invert the can (bottom up) so it pulls the liquid freon in... Don't fill without a gauge (no matter what your brother's uncle says) as you'd risk an over charge.