Volvo Repair: Air cond. on 97 & 98 S90, vacuum problem, compressor clutch

Question
I have 3 problems,  on the 97 the dash vents shut off when I accelerate. I'm sure it's a vacuum problem but where do I look?

on the 98 after a 3-4 hour drive the AC starts blowing hot air after about 7 miles it blows cold again. I have not checked anything it just started.

also on the 98 I need to replace the sun roof selector gates.  Do you have any tips?

Answer
the 97 has a problem with either the recirculation or the bilevel vacuum diaphragm or both.both are somewhat difficult to replace.

the 98 A/C problem more than likely is a bad compressor clutch that is shutting off when hot.to check it check for power at the clutch wire on the compressor. if it has power and the compressor is not running it is a bad clutch.

the selector gates only tip is do not use all the parts given with the new one.it is easier to do by replacing just the gate and not the slide piece it is attached to.

I would get help or more instruction in person if possible.If possible stop by the dealer and talk to a technician.