This spring the AC on son's 850 decided to act up. 2 years ago I had installed a rebuilt compressor and receiver dryer and all was well. This year the system acted as if it was overcharged, but would not cool. Finally we jumped or bypassed the low pressostat and the system took a charge and cooled perfectly. Purchased a new pressostat (give away item of $56 with discount) and all is well.

Have not heard much in these little guys going bad, but this may help someone on the diagnostics. BTW, parts man said low and high pressostat's are the same.

Volvo # 9171700 May be the same on S70's too.

dick

The pressostats are not the same, at least on my '98 V70. The 2-terminal switch by the firewall is just a switch -- closes at 45# to allow the compressor to run, and opens at 20 or 25# to stop it. The 3-terminal one near the fill port is a pressure transmitter that gives a pressure signal to the engine control module.

Thanks. Pressostats do fail, and when they do the compressor will not engage.

Klaus
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The more I learn, the more I forget. So why learn?