Volvo 940

A friend of mine just came to me with a problem he's having with his
940? When he accelerates the air coming from the vents shifts from the
face vents to the floor. When he's accelerating uphill it does the
same. When he's going downhill it never happens, although maybe this is
due to most people not accerlating too much on downhills.

He recently had the timing belt changed and the problem surfaced only
after that work. I'm guessing this is some sort of a vacume problem.
Any thoughts/suggestions? Are there hook-ups for vacume lines in the
engine bay or are they all within the heater box, within the dashboard?

Thanks for the help,

Kevin

kevinhorgan1 "at" hotmail.com

 

The servos that open and close the vents are vacuum operated. When the
system loses all vacuum, they go to their relaxed positions. Either you
have a vacuum leak, or the check valve that prevents the vacuum from
"leaking out" when the intake manifold vacuum drops (as during
acceleration, or going up a hill). The first place I'd look is at the
heater valve, which is mounted in a heater hose, up against the firewall
just toward the center of the car from the brake booster. Then make a
general check of the other vacuum line that takes vacuum to the controls
through the firewall, and the check valve in that line.

If you have the 940SE, (or electronic climate control) then there's a
servo by the driver's foot (on the other side of the kick panel) that
fails. This is very hard to replace, but if you disconnect and plug the
hose going to it that causes the leak, the system still works well.