Air vents 79 450SL

[jr811]

I"m not getting any air out of my center vents, side vents working OK,
anyone had this problem? Jim

[Bondavi]

Have you tried the air inlet open/close slider right below the air vents? That controls the airflow, at least for the center.

If that has already been covered, and your car has an automatic climate control system, then the servos would probably be the culprit.

If it is your climate control servo, you might try replacing it with the digital servo that is available from Performance Products. It replaces both the servo and the heater valve. I put mine in about 4 months ago and so far it is working fine. Be careful though, the nipples on the vacuum control valve are soft and tend to bend easily when slipping the hose over them. Be sure to lubricate the vacuum line when assembling.

[450sl4me]

My 1980 SL vents blow sometimes but not all the time, except if the AC is on. If the AC is on, it always blows. But if I just want fresh air, it is intermitent. Is this the servo? Where exactly is the servo and how much does it cost? How hard to change?

[Lawrence Coppar]

You could have a vacuum leak in the system. When my SL was only several years old, the arm from the actuator that controls the center vents broke. You can get to the actuator by removing the instrument cluster. Actuator is left of center. Check actuator for vacuum leaks.

The servo valve is on passenger side near firewall. Expensive and a piece of crap that causes trouble. I went through three of them before buying an aluminum one from G. Murphy.