Hi,

I own an Australian 1979 280E, with non climate control air conditioning, with the temperature dials seperate for the driver and passenger. My drama is that no amount of turning the temperature knobs (cold/hot) makes any difference to the air temperature coming out of the vents, with or without the air conditioning being on, both vents just blow warm air, so obviously something to do with the control knobs not opening and or closing the necessary doors/flaps is whats wrong.

Is there a way I can find out how to fix the problem?

Thank you

The 2 temp dials are for the heater only. Warm air comes in thru the footwells and side dash vents when opened, for defrosting the side windows. Main defrost works when you select defrost with the upper-console slider and set the same 2 temp dials.

AC temp is controlled by the A/C roller wheel. This air comes in thru the 2 middle dash vents.

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Thank you even when the ac is off there is warm air coming from the dash vents, I tried different settings with and without the ac on and there is no difference in temperature

In this case, I suggest that you check the heater shut-off valves on the firewall to to be sure they are completely off when the dials are off.

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Thanks any idea where I can find them? Totally new to mercs

On the firewall just behind & above the right camshaft for both left & right-hand-drive cars.

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Thanks I found it

The cables are operating the levers, but they are spinning and not actually moving the valves, plus 1 of them broke where the lever joins onto the valve D'OH

Anything I can do now?

Thank you

Hello,

If I recall only the W114, W115 cars have the shut off valves on the firewall in the engine compartment. The W123 cars have them under the dash, behinc the console?

Sounds like a cable is broke or disconnected.

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Joe Alexander
Blacklick, Ohio
1964 220SE Rally (La Carrera Panamericana someday)
1966 Unimog 404s (Swedish Army)
1969 300SEL 6.3 (sold)
1969 280SL Pagoda
1973 280SEL 4.5
1974 450SLC FIA Rally car (standard trans)
1982 300D turbo (winter driver)
1986 560SEC
1989 Unimog FLU419 (US Army)
1991 300TE (wife)
2002 SLK 32 AMG (350 hp)

Just replace the valve. You should be able to find one at a wrecking yard, or here on this site someone probably has a used one for sale. They are not expensive. Any valve for a manual W123 heating system will work.

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