Defrost only on all heater setting modes

[autoworrks]

On the last drive i took in my 93 500e just before storing it for the winter i noticed there was only defrost available from any heat settings. Can anyone advise what to check for.

 

[gsxr]

Do you mean that warm air only came out the defroster vents (and end dash vents), nothing from the footwell vents? If so, there's a vacuum problem; either lack of vacuum source to the air flap controls, or a defective footwell pod.

 

[autoworrks]

where do i start

 

[gsxr]

I'd start by looking at the vacuum line that goes through the firewall, near the brake booster (I think it changes to green color at the firewall, but may be clear tubing to the engine). Trace it back to the engine and make sure it's connected to the intake manifold. Next up, check all the fuses; if the electrical portion isn't working right it won't trigger the solenoids for the vac pods.

After that, I'd pull the passenger airbag and test all 7 lines at the solenoid manifold with a MityVac. It's common for one or more of the vac pods to fail after 15+ years. Only the footwell and defrost pods can be replaced easily, the others require pulling the entire dash... not fun. Check the simple stuff first though.