Hi, I posted this in an old thread --- https://volvoforums.com/forum/volvo-...-issues-85843/
but thought I'd just make a new one so it's easier to find.
My ac hasn't worked in ages and I thought I'd finally tackle it. I unplugged the low pressure sensor and tested at the plug. I have power to one lead of the plug at the low pressure sensor when the climate control is engaged. I jumped the other lead to the positive end of the battery and the ac clutch engages and blows cold air.
So I know I have power at the plug, and I know the compressor works, and I know there is continuity from the plug to the compressor, so I thought the sensor must be the issue.
The problem is that I tried jumping one lead of the plug to the other, and it doesn't work, so maybe the sensor is fine? I am totally confused how one end is getting power, and the compressor works fine when I power the other end, but it doesn't work when jumping it. The only thing I can think of is that the battery has 13 volts and the plug has 11 volts, but is that a big enough drop where the compressor clutch won't engage? Could the plug lead have the voltage, but not have the amperage to power the clutch?
Maybe there is something obvious I am missing in my test?
Thanks.

 

for some reason the climate control wouldn't supply enough current, so I jumped it to the cigarette lighter with a switch lol. problem "solved"

 

Your style of climate control - is subject to a cracked solder joint on the circuit board in your "climate control module". There is a power relay and power to the compressor is interrupted by a cracked solder connection where the relay is connected. I have fixed many with a solder gun.

This post and many others may offer a cleaner solution that what you have.

https://volvoforums.com/forum/volvo-...-module-63210/