W124 Climate control failing

[Jim Cross]

My 1992 300 TE4 is only blowing air though the defrost and side dash vents.
I understand I will need to replace some of the vacuum controllers.
Is it a good practice to replace all the diaphragms (6?) at this time or just do what is needed?
Would also appreciate any tips on this project

Thanks
Jim

[jcyuhn]

It's best to diagnose the problem before making that decision. Diagnosis is easy, especially if you have a glovebox rather than a passenger airbag. If you remove either - glovebox is easier and less likely to explode - the switchover valve is staring right at you. From that point you can test each of the seven vacuum lines running to the various actuators in the system. A small hand-held vacuum pump (AKA mity-vac) is the way to go here.

On a 124 the defrost actuator is the only one you can replace without removing the dashboard. However, if that's your problem, I would suggest changing only that one. Again, it's perhaps a 30 minute job.

Given the age of your car, most likely you'll find two or three of the seven vacuum lines leak down. In that case, the dash will require removal to replace the failed vacuum actuators. If you're going to pull the dash, then just replace them all. The additional parts and labor cost is minimal relative to the expense of pulling apart the interior of the car.

My $.02,

- JimY

[Jim Cross]

Jim

I have an airbag where the glovebox used to be so
it looks like a complete dash removal for me

Thanks
Jim

[J.HIDALGO]

the air bag can be removed before the dashboard. However, if you are going to remove the dashboard, replace all of them. You are already there.