My 06 Saab 9-3 air conditioning is not working. The compressor is free and turning but will not engage. The pressure sensor has current and seems to be activating. I took it to a garage and had them evacuate and fill several times and the compressor still won’t activate. Could it be a wiring thing or is the compressor messed up?
When you say the compressor is free and turning, do you mean the pulley or did you turn the clutch plate to actually turn the crankshaft? Have you had the car scanned for codes using a Tech2 or equivalent scanner? The trouble is that on modern cars it's not enough for the mechanical parts to be working, the complex electronic controls have to be working as well.
If everything is OK with your AC mechanically it means the electronics or wiring are faulty, or possibly the clutch coil. With the engine off you can hotwire the clutch coil and see if it engages the compressor clutch. If it works and you are absolutely certain that the compressor is not seized up and you have sufficient refrigerant you can engage the compressor clutch with the engine running to see if you get cooling.
The pulley and clutch plate are free. There are no codes with the tech 2. I just got robbed at a GM dealership telling me they don't see why the compressor is not engaging. I asked if it was a wiring issue, and they said that I should just get a new compressor and pressure switch. I don't want to unless I know THAT is the issue.
P.S. I only took it to a GM dealership because my trusted garage couldn't find the issue and no one else wants to touch a Saab
In a lot of ways it's not much different than other GM cars of the same vintage. However if the GM dealer was not a former Saab dealer they might not have had the Saab software for the Tech2. (The Tech2 is not like modern scan tools that can work on just about anything. You have to have the software on a linear PCMCIA card inserted in the tool for the car you're working on. Saab and Saturn both use different Tech2 software than other GM vehicles, and of course overseas GM models have their own software.)
Orio (formerly Saab Parts) still maintains a network of Saab service centers. If one of those is not too far from you that would be a better bet than a generic GM dealer. (Of course they are mostly concentrated in areas where Saabs were popular like the Northeast.)
https://saabparts.com/us/book-a-service/
You might also find some specific help on that model on Saab forums. (Although I've been driving Saabs for something like 40 years now they've all been pre-GM models. I have not worked on a 2nd-gen 9-3 like yours.)
https://www.saabnet.com/tsn/bb/9-3/
https://www.saabcentral.com/forums/9-3-sedan-cabrio-04-combi-9-3x-workshop.30/
As an experiment to see if the clutch coil is working you can try hotwiring it to the battery and see if it works. If it does you have either a wiring issue or an electronic module issue. If the clutch works and hotwiring the compressor provides cooling one option would be to put it in a manual switch as Scotty has talked about to bypass failing electronics.
https://www.youtube.com/watch?v=0Foh6IF9Z5I