INTERIOR HEATER ONLY BLOWING HOT AIR FROM VENTS

[MLFLY]

HI TO ALL,

IM NEW HERE,

JUST WONDERED IF ANYONE HAS ENCOUNTERED THIS PROBLEM

HAVE A 2015 W166 ML 63 AND THE HEATER ONLY BLOWS OUT HOT AIR AS IF SET AT 28 deg CONSTANTLY
EVEN IF TEMP SET TO 16 deg ON THE DIAL

ANY INPUT AND ADVICE WELCOMED

THANKS
MLFLY

 

[rockits]

I had this on my E55K a while back and it seems a fairly common issue possibly with the heater control valve. The seals break down over time and it lets some moisture in then gradually corrodes the internals. Pretty cost effective part to replace if it is the same is mine. I had the opposite in that it was only blowing cold and not hot as the valves seem to get stuck in a position when the motor fails to operate the valve any more. Changed the heater control valve on mine and it was perfect after that.

 

[rockits]

I think it cost about £50 and looks like this pic attached.

 

[rockits]

This was a pic of mine inside.

 

[MLFLY]

Thanks for your message

I will look into that

And let you know my findings

 

[MLFLY]

I had this on my E55K a while back and it seems a fairly common issue possibly with the heater control valve. The seals break down over time and it lets some moisture in then gradually corrodes the internals. Pretty cost effective part to replace if it is the same is mine. I had the opposite in that it was only blowing cold and not hot as the valves seem to get stuck in a position when the motor fails to operate the valve any more. Changed the heater control valve on mine and it was perfect after that.

Hi Rockits,
Did your problem with the temp control valve unit look similar to what described in this report section?
Thanks
MLFLY

 

[rockits]

To be honest mine was simple in the sense that the system was working as far as I could tell and doing all the right things. Just that it was only kicking out cold but the pipes to the heater control valve felt hot. I never had it hooked up to a diagnostic device to troubleshoot.

After some research it seemed to be a common problem and I could see no details of the part ever being replaced on my car from new. So as I knew it was likely the original part from new, after 20 years and just over 100k miles I thought it was not a bad thing to replace anyway.

It was only about £40 for the part and just a couple of hours labour to change. So was worth the punt as the first option to see if this was the culprit. Luckily for me it was and everything was perfect after that and has been ever since.