1975 280C: no heat or airflow when turning "defrost" switch

[travismcgee]

Hello, I am new to this forum because I am new to MB ownership. Just bought a 1975 280C (Engine:110.921; Chassis:114.073. It is actually my son's first car.

The problem is when I turn the "defrost" knob no airflow comes out of any of the vents. When I turn the AC knob air does flow from the vents (the AC compressor is disconnected). Are there two different fans for heat and AC? Is there a heater core tucked away inside the car? When I touch the hoses going into the firewall they are hot.

I do not have an owners manual so I am not sure of the configuration of the sliding blue and red controls on either side of the "defrost" knob to bring heat into the car.

I hope my questions are specific enough and appreciate any help offered.


Cheers,

Travis

[Takernz_30]

does your car equipped with auto climate control? my car, 1966 200 is equipped with manual controls,(swinging that little handle along the long slots above the radio) I think they share one fan for both AC and heater. There's a gate which connected from a lever by cable that swings that diverts air to AC and moving again the lever and swings another for heater.

[JimFreeh]

Originally Posted by travismcgee

Hello, I am new to this forum because I am new to MB ownership. Just bought a 1975 280C (Engine:110.921; Chassis:114.073. It is actually my son's first car.

The problem is when I turn the "defrost" knob no airflow comes out of any of the vents. When I turn the AC knob air does flow from the vents (the AC compressor is disconnected). Are there two different fans for heat and AC? Is there a heater core tucked away inside the car? When I touch the hoses going into the firewall they are hot.

I do not have an owners manual so I am not sure of the configuration of the sliding blue and red controls on either side of the "defrost" knob to bring heat into the car.

I hope my questions are specific enough and appreciate any help offered.


Cheers,

Travis

Congratulations, you're about to embark on the one of the most time consuming jobs on a Mercedes.

Yes, the A/C and the heat have separate fans.

The A/C fan is located at the base of the console, below the radio.

The heater fan is located in the center of the car, requiring hours of disassembly to access. If you remove the cowl panel between the hood and the windshield, you just about see the fan and might be able to dribble some oil on one of the bearings. I've had mixed results reviving the fan that way. Otherwise......

Good thing is, the airflow thru the heater/defrost is pretty good once you are moving. Kinda like an old VW beetle, which relied on on car movement, without a fan.

Jim