R-Class 320 heating system

[Motzil]

Hi need a little advice got a 2009 R-class now the weather’s taken a turn for the worst. Set the heater control to max and blower on medium. Clears the windows when frozen brilliantly.

But some 20 minutes later the heater is not as hot as I would expect it to be. I’ve checked to make sure there is plenty of water in the header tank, which there is. Only had the car since April. So heater controls have been set to cool looked in the manual and setting seem to correct.

I’m I missing something here, or is there another underlying problem that I need to be checking

many thanks in advance

after reading a few more post it appears my car could have a heater control valve connected to the heater matrix at the bulkhead. Is there a way to test this..?

 

[mioba]

If the AC system is on auto, once things have reached temp, the air flow and temp will reduce. Doesn't sound like anything wrong to me

 

[Motzil]

Many thanks for the reply mioba I will check it out. May just be me now that its come cold all of a sudden. Will check it out over the next week. I take that if I take it off auto and set the temp to 28 on both sides it should get hot within 20 mins

 

[LostKiwi]

Check your engine temperature. Cold engine = cold heater.

 

[EmilysDad]

Many thanks for the reply mioba I will check it out. May just be me now that its come cold all of a sudden. Will check it out over the next week. I take that if I take it off auto and set the temp to 28 on both sides it should get hot within 20 mins

You can set it to what ever temp you like & still leave it in AUTO

 

[Motzil]

Ok guys we’re a year on and still no joy. The blower is working fine if I select auto it will select air con if I select the blower and heat direction auto switches off.

so all appears o work as it should but it will only blow cold air. Temp gauge is showing 90C so having it set to 28C should be no problem.

can anyone shed some light on this please

 

[EmilysDad]

blocked heater matrix maybe ....

 

[Motzil]

blocked heater matrix maybe ....

Hi Emilys dad

I had been thinking along those lines. However about 8 weeks ago I was playing about with the controls trying to see if it was the In-cab sensor and it suddenly started to blow lovely warm air. This lasted a few days.

When the wife gets in she alway turn her side to cold. I have been reading on a few other sites that it could be be the heater control valve which is under the bonnet somewhere. Not a great deal of room under there to look if you don’t know where it is

I have also read it could be the blend door mechanism. Which can be fixed by removing the radio and glove box and a small can of silicone oil.

But I have read some nightmare stories of people having to do full dashboard tear downs and looking at the pics that’s a big NO NO

Going to try and locate the blend door mechanism first if no good gonna have to find a good Merc specialist who doesn’t charge the earth to look at it. Apparently it looks something like this

 

[EmilysDad]

I only ever had one problem with the heating on my R Class .... one hot afternoon after work, one side was blowing hot, the other side cold. Turning the heater control from hot to cold to hot to cold 'fixed' it and I never had any other problems.