R107 heating not working

[davidjpowell]

Father in law has a 280SL which I'm told is operating at normal temperature however he's getting no heat in the cabin.

Is there any place to look for a typical problem?

 

[Druk]

There is this valve on the engine bulkhead right side. Vacuum operated from the outer levers on the heater panel when they're at their lowest point.
For the life of me I can't remember if it defaults to open or shut when the vacuum fails but it's your first point to check. It's common for a vacuum pipe to come adrift at the point where they all join up behind the battery.

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[Ierton]

Also common for them to fail completely and drain the coolant. About £40 from memory though that was a fair few years ago when I replaced mine.

 

[davidjpowell]

There is this valve on the engine bulkhead right side. Vacuum operated from the outer levers on the heater panel when they're at their lowest point.
For the life of me I can't remember if it defaults to open or shut when the vacuum fails but it's your first point to check. It's common for a vacuum pipe to come adrift at the point where they all join up behind the battery.

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Well the vacuum is working and the arm moving....

 

[Druk]

OK. The whole 107 system works by air mix. That valve is either on or off so if it's working it must be a flap stuck somewhere. Which is a bit more of a handful to diagnose

I've had a 280 for 10yrs and never had a need to bleed it so hoping it wont be that. The usual complaint is that they won't blow cold.

Before you go delving it might be worthwhile to disconnect the hose from the valve and check if it's working internally. It is just a simple shutter valve though so not much to go wrong. Use two brake hose clamps on the hoses to minimise water loss.

There are two rods that go to the air mix flaps at the side of the heater box. You have to take either the glovebox out or the undertray down. There is a pinchbolt where the rod joins the flap lever. See if it's loose.


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