W124 Heater

[Chippydad]

Hi all. Problem with the heater, blows hot contiuesly. Control wheels are on mim. Phew!! what a scortcher.

 

[mike65]

Could be the duo (or is it mono) valve being stuck open?.

Mike.

 

[C220GJS]

Duo or mono valve defaults to open without power so check power feed to the heater system.
Geo.

 

[Chippydad]

Thanks chaps.....How do i find the duo valve and is it very accesable?

 

[Richard Moakes]

Open bonnet, look by brake servo, it's almost directly in front of driver.

You will see numerous pipes, but what you are interested in is a block connected to the pipes with what look like two silver cotton reels on it, those are the solenoid valves. Later cars also have an auxilliary electric water pump on the same block, earlier cars have it in the engine compartment near the washer bottle reservoir.

As was said, I would check for fuses....is it fully automatic ACC ? How many push buttons? 3 is conventional system, 5? I think is the more complex ACC, which can burn out and lose control of the solenoids.

Richard

 

[Chippydad]

Cheers, thats very helpfull. Its getting dark now ill check in the AM.

 

[aaron6155]

as the other person mentioned check the power supply but replace the fuse for the heating system first, even if it looks ok it may be corroded slightly and will be well worth trying.

 

[Chippydad]

You are all super.....Fuse, in its socket it looked fine, took it out and noticed a rusty end and it then broke, replaced it with a good`en and hey presto.....cool man. OK, Halfords today not MB dealer tomorow......Cheers!

 

[mike65]

Is'nt it great when its a 30p item and not a 300 quid bill?!

Mike.

 

[C220GJS]

Yippee!!, always look for the simple fix first. Fuses on these cars are a known problem area ,best to replace the lot.
Geo.

 

[Richard Moakes]

Ah yes, I replaced all of them about 6 months ago, some of them looked very original and corroded when I removed them.

 

[johnnycapone]

I have the problem that the drivers side heater will operate ok but the passengers side will only blow cold.
Tried the simple things like giving it a thump but to no avail.
Now the weather is getting a little more clement, I might try and strip the duo valve and take a proper look.
Regards
John

 

[C220GJS]

I have the problem that the drivers side heater will operate ok but the passengers side will only blow cold.
Tried the simple things like giving it a thump but to no avail.
Now the weather is getting a little more clement, I might try and strip the duo valve and take a proper look.
Regards
John

First, to rule out any electrical problem, unplug the duo-valve, your heating should then run hot on both sides, if not the problem is probably a seized valve.
Geo.

 

[Richard Moakes]

First, to rule out any electrical problem, unplug the duo-valve, your heating should then run hot on both sides, if not the problem is probably a seized valve.
Geo.

Wise, simple and cheap advice.

The lost art of diagnosis, seems like most garages can't do this anymore, unless they can plug in a computer and it tells them what's wrong, then they are stumped.

Richard

 

[television]

Wise, simple and cheap advice.

The lost art of diagnosis, seems like most garages can't do this anymore, unless they can plug in a computer and it tells them what's wrong, then they are stumped.

Richard

So true Richard, its going to get worse with all of the new inavations waiting around the corner, if it is the duo valve, they can be purchased in the USA much cheaper than here.

Malcolm

 

[C220GJS]

I'm going to the US on holiday in August,maybe we could make up a bulk order and I could bring them back as hand baggage.LOL.
Geo.

 

[kanda]

Thanks chaps.....How do i find the duo valve and is it very accesable?

It is near the fuse box, You can see a hose going into it.