DIY: R230 Heater Control Valve

[i_york]

I just acquired an SL55 and one of the first jobs to tackle was the heater only blowing cold air (not ideal this time of year!) If you have these symptoms, or if the heater only blows hot, the heater control valve is very likely the culprit.

Tools you'll need for the job:

New heater control valve (p/no A2308300084, £45 from Mercedes)
15mm, 13mm and 10mm sockets
Wiper arm puller
Water pump pliers

Time you'll need for the job: 1-2 hours.

Put the bonnet up into the service position using the catch on the passenger side bonnet hinge:



Remove the wiper arms (3 x 15mm nuts under protective plastic covers). The arms need a puller to remove from their stubs

Remove the scuttle panel (this just clips in place)

Remove the windscreen wiper assembly (3 x 13mm nuts):





I also removed the following bracket (2 x 10mm bolts) to make this easier:





Note the wiper assembly may need a gentle pry to release it from the threaded studs, depending on the degree of corrosion present.

The heater control valve is now visible on the driver's side adjacent to the master cylinder reservoir:



Remove the electrical connector.

Now comes the awkard bit due to the cramped conditions... using water pump pliers, reach-in and ease the hose clamps back on each of the 4 hoses that connect to the heater control valve

Remove all 4 hoses from the heater control valve (no need to clamp them off) and remove the old valve

Install the new heater control valve and run the engine to check for leaks and correct operation before reassembling the wiper assembly, etc.

This is what the inside of my old valve looked like:

 

[Vlad]

Just done this job and following the guide from above which was very useful

Have to say it was a horrible task.

All very easy until the removal of the pipe clips. Very tight access and and once the pipes were off the most difficult part was reattaching the pipes and clips onto the new valve.....what an absolute pig of a job. Slippery pipes due to coolant leaking onto them and only a short stub of pipe to try and reconnect and then having to get the pipe clips back on....ARGH

Had to walk away from the job a number of times and calm down and reapproach with fresh eyes.

 

[Gnmelectric]

Just done this job and following the guide from above which was very useful

Have to say it was a horrible task.

All very easy until the removal of the pipe clips. Very tight access and and once the pipes were off the most difficult part was reattaching the pipes and clips onto the new valve.....what an absolute pig of a job. Slippery pipes due to coolant leaking onto them and only a short stub of pipe to try and reconnect and then having to get the pipe clips back on....ARGH

Had to walk away from the job a number of times and calm down and reapproach with fresh eyes.

you were fk** ng yourself
maybe your cars are made different in the UK but this threw me out too

the instructions are just bad instructions; why would you remove all that stuff from the top when you can get in there from the front and have full control
remove the metal behind the engine it's RIGHT THERE on your left side.

 

[design guru]

Good write up, Very surprised how cheap the part was from Mercedes. I know what you mean about the pipes!