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Lou P. master tech
Lou P. master tech, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4834
Experience:  15 years master certified 100% fix rate and have access to factory radio codes, wiring, and instructions.
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Hello, my name is***** and i will do my best to assist you.I am going over your story now and will reply back soon with some info,thanks!

Mel when you say heater are you talking about the fan or the temperature of the air coming out?

Customer: replied 11 months ago.
The temp. Fan is ok

ok, what temp did you have the car set at? on your model you can set the front temp to achieve the same temp for driver and passenger or individual temps for driver and passenger .

Customer: replied 11 months ago.
Both sides were set at highest temp in front. I can control the rear, but not the front. Both sides are affected. AC is ok. I'm a mechanic, but not much Mercedes experiance.

ok sorry for my delay, we had a bulletin for the heater core being clogged, for some reason mercedes put a silicate bag in the reservoir and they tear open and clog the heater core, if not that then there is an additional water pump that helps push coolant through the heater core that can fail, with a mercedes the best and first route to always take is to get a mercedes scan tool that can read all the control modules not just the engine and transmission as most scanners do. without knowing the codes there are too many options for possibility . so for starters always get the codes read then we can proceed from there, but i always check the heater hoses near the firewall to make sure the hoses are in fact hot. hope this helps. i will get you any info you need but this is not a common issue so it will take some time to diagnose. Lou P.

Please take a second and click the stars at the top of the screen to rate me so i may receive my credit , 5 stars is ideal , please request me in the future.
Keep in mind then when you rate it does not end our conversation. you can still return here to me for follow up information if needed, Lou P.

Customer: replied 11 months ago.
If the heater core was clogged. I would think the rear heat would also be affected. Do they use separate heater cores for front and rear? I don't have a Mercedes scan tool.

two different heaters.

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