I have a 1995 940 turbo, 105,000 miles. I very get little air from dash vents. Defrost and footwell get most of the airflow. A/C is charged and does get cold. I checked the vacuum line from intake, check valve (works and is not in backwards) and checked vacuum line after the check valve down to the firewall. I used a vacuum pump and gage and found those lines hold vacuum. I also checked the port in the intake for vacuum line and it pulls a vacuum. I then pulled the HVAC controller out of the dash and checked all the lines running to the controller and there is no vacuum at any of the lines with the engine running. I then put vacuum to the 4 lines that run to the bellows and they hold vacuum and operate properly with the vacuum pump and change the airflow to the correct vents when under vacuum. So my question is what do I check next. Also I can't find which line to the HVAC is the vacuum line. If I knew which line supplied vacuum to the HVAC controller I could test its operation and rule it out. My thinking is since there's no vacuum getting to the HVAC controller the problem is between the accumulator and the HVAC controller, unless there's another valve between the one that's inline between the intake and firewall. Any suggestions on where to look next?

 

If you have ECC (climate control) You have vacuum to 2 of the ports on the firewall as pictured below? 1 port goes to the vacuum controller in 2nd picture, 1 port goes to the temp sensor in the dome light, and the 3rd port sends vacuum back out to turn the heater valve on and off.

Find the other side of that port plate on the firewall - and trace it back to the vacuum controller. Probably a collapsed vacuum line. Aren't they color coded? Or do you have MCC (manual climate control)? 2 Vacuum lines enter on the left side of the firewall on those. (3rd picture) 1 for the heater valve and the other for vacuum to the controller built into the control panel. .

 

hoonk, thanks for the help. I traced the vacuum line through the firewall and found it capped off. There was only about 2 inches of the line sticking through the firewall. When I pulled the cap off the line I could see it had been cut. I felt around and found the other end of the line. I cleaned up the ends and patched them together with a short piece of rubber tubing. All HVAC systems now function properly (too bad I didn't find it before disassembling the center console). Still wondering why someone cut it in the 1st place.

 

A common problem is the floor vent servo mounted low on the drivers side leaks - and face level vents go away due to loss of vacuum when accelerating. Someone may not have known you can simply disconnect and plug the floor vent servo hose to solve that problem.