A/C Compressor not engaging, any ideas?

2000 Volvo VNL 64T
N-14

My Blower motor went out, so I thought. I went down there and found a loose pin on the jumper harness. I Fixed that.

my a/c compressor is not getting power, so it won’t engage. I tested for power at the plug, truck side. I have put 12v power direct to the compressor and it will engage.

I have a new a/c on off switch. When I press it, the relay will click. Can a relay still be bad if it clicks? I’ve replaced the relay with a spare used one I have, still no juice to the compressor. The fuse is good, and so is every other fuse I got in the box.

I wanted to ask, am I missing something? Tomorrow I’ll go buy a fresh relay to see if that’s it. From the relay, I don’t know where else it would go besides straight to the engine harness / compressor itself? There is what seems to be a blend door involved too. I should of tested it for power. I did replace the blower motor resistor too, because I guessed wrong on the first diagnosis of the blower motor. Any ideas? Thanks!

 

Do you have a temp sensor to the right of the ash tray?

 

I went through the same exact issue, changed pressure switches, relays and whatever. Thought I fixed it, but then it would start acting up again.
Eventually got the temp sensor out, cleaned it and everything works now, but AC only kicks in when temp inside cab is above 60 degrees

 

Idk, do either one of these two look like the temp sensor you remember? One on top of the 12v cig lighter, and the other is built into the a/c module piece.

 

What's the A/C static pressure?

 

It's to the right of ash tray opening behind a little grill

 

You also might have bad hot/cold valve, see if the metal string is all the way down on it, when your AC switch is in cold position

 

Could this be the valve? Or is that more like a temp sensor? I see the metal line going into the condenser, maybe to read temp? It’s got two electric leads to it.

 

It doesn’t look like that’s where mine is, unless I’m really overlooking it maybe lol (i looked deep in and around)

 

Ahhh. Good question. I don’t know that was even such a thing I must say how does one check that? And what does that reading help to see?