W212 Theromtronic Climate Control Failure + LOUD Engine fan
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E Class W212
W212 Theromtronic Climate Control Failure + LOUD Engine fan
This is a problem I have solved, but I want to post it just for the benefit of any future forum visitors who may have the same issue.
• Climate Control Unite (Thermotronic Dual Zone) died a slow death on my W212.
• First the row of buttons would only work pressed upwards, then a few days later, the whole unit died.
• After it died, the check engine light came on.
• After that, the engine fan would blow full blast when I was driving.
Unsure why or how the engine fan and climate control are linked, but they are it seems.
I changed the unit for a second-hand one off eBay, £35. I made sure all the serial numbers on the back matched the ones on the ebay one. It was from a coupe; mine's a saloon, so the outer casing was different, but a few screws and you can get the PCB out of the unit and put it in your existing unit. It can also help if the one you are buying is a scratched-up mess as well.
After I put the new unit in, it turned on fine, all buttons worked etc, the heaters now blew, and the fan on the engine stopped blowing. The engine light did stay on, but I have just driven it a few hours later, and the light has gone off.
A word of warning, though – be careful putting the screws back in the dash. I dropped one, no idea where it's gone behind the dashboard. I hope it doesn't get in the way of anything or rattle around.
• Climate Control Unite (Thermotronic Dual Zone) died a slow death on my W212.
• First the row of buttons would only work pressed upwards, then a few days later, the whole unit died.
• After it died, the check engine light came on.
• After that, the engine fan would blow full blast when I was driving.
Unsure why or how the engine fan and climate control are linked, but they are it seems.
I changed the unit for a second-hand one off eBay, £35. I made sure all the serial numbers on the back matched the ones on the ebay one. It was from a coupe; mine's a saloon, so the outer casing was different, but a few screws and you can get the PCB out of the unit and put it in your existing unit. It can also help if the one you are buying is a scratched-up mess as well.
After I put the new unit in, it turned on fine, all buttons worked etc, the heaters now blew, and the fan on the engine stopped blowing. The engine light did stay on, but I have just driven it a few hours later, and the light has gone off.
A word of warning, though – be careful putting the screws back in the dash. I dropped one, no idea where it's gone behind the dashboard. I hope it doesn't get in the way of anything or rattle around.
Out Of Control!!
Joined: Apr 2019
Posts: 11,921
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Well done ! 👏
Good job on getting your HVAC module back in top shape.
Instead of replacing with a used unit, perhaps you could have resoldered the collection of loose circuit pins for free.
One thing that puzzles me with HVAC module is its stealth abilities.... it can have blank data and not throw any fault code. So look deeper for missing/bad data.
The speed of the engine fan is linked to AC demand level. For engine safety, the radiator fan can race to near supersonic cooling.
Instead of replacing with a used unit, perhaps you could have resoldered the collection of loose circuit pins for free.
One thing that puzzles me with HVAC module is its stealth abilities.... it can have blank data and not throw any fault code. So look deeper for missing/bad data.
The speed of the engine fan is linked to AC demand level. For engine safety, the radiator fan can race to near supersonic cooling.
Last edited by CaliBenzDriver; Mar 9, 2023 at 01:56 PM.
