Our 2004 S60's air conditioning cooled well but would drop out every 10-20 minutes and I read about removing compressor shims or adding bread clips or wire ties to tighten the clutch gap. Then I read about adding a DC-DC voltage booster to which is essentially "shimming" the voltage which seems reasonable for maybe a 10% increased voltage.

https://www.matthewsvolvosite.com/fo...ic.php?t=77585

I probed the back of the harness connector in the fuse box and confirmed that grey was the clutch function. The AC still worked. Then I unplugged the fuse box harness connector to check the wire length without disconnecting the battery. I re-plugged it but did not check AC function. I disconnected one of the chassis ground wires near the fuse box and added a ground connection for the booster. I connected the voltage booster and I -think- I only connected it to chassis ground and the + grey wire as input; I had not cut the grey wire. Something on the DC booster smoked. At that point I disconnected the device, started the car and got a Engine System Service Required message on the dash. The AC did not engage. I powered everything off, waited 10 minutes, disconnected the battery, waited 10 minutes, reconnected and still have the Engine System Service Required message. The AC clutch will still not engage. I do not find any trouble codes with my basic Actron code reader.

Where to go from here?