No Heat Coming, Just Cold Air - 2009 C350
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MBWorld Fanatic!
Joined: Jun 2007
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From: Los Angeles, CA
2015 C400 Tenorite Gray
No Heat Coming, Just Cold Air - 2009 C350
After warming up the car, no heat comes on. It just blows cold air. Set to auto on the hottest temp does nothing. I'm here in Los Angeles so frozen water trapped is not an issue.
I suppose a bad relay would not produce a CEL.
Has anyone dealt with this?
I suppose a bad relay would not produce a CEL.
Has anyone dealt with this?
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From: Ontario, Canada
2009 C63 AMG, 2010 C250 4Matic Sport
You might want get the heating shutoff valve looked at to verify it's working properly - It's at the back of the engine on the drivers side near/somewhat underneath the vacuum pump
Thread Starter
MBWorld Fanatic!
Joined: Jun 2007
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From: Los Angeles, CA
2015 C400 Tenorite Gray
Thread Starter
MBWorld Fanatic!
Joined: Jun 2007
Posts: 1,022
Likes: 44
From: Los Angeles, CA
2015 C400 Tenorite Gray
Super Member
Joined: Oct 2014
Posts: 701
Likes: 103
From: Ontario, Canada
2009 C63 AMG, 2010 C250 4Matic Sport
It won't show a CEL, a fault might be stored either in the HVAC control unit or the engine ECU though.
I accidentally left my heater shutoff valve unplugged when I put in my new intake manifold, and never got any codes or errors at all..
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From: Los Angeles, CA
2015 C400 Tenorite Gray
So I ended up replacing the thermostat and that solved the problem. Now it's back.
FCP Euro says to change out the thermostat every 50,000 miles.
That seems premature.
With today's case and the previous case, the car temp went up a little but not much.
The fan comes on occasionally.
I always thought a failing thermostat lead to major overheating at some point.
Opinons?
FCP Euro says to change out the thermostat every 50,000 miles.
That seems premature.With today's case and the previous case, the car temp went up a little but not much.
The fan comes on occasionally.
I always thought a failing thermostat lead to major overheating at some point.
Opinons?
Last edited by Nicholi2007; Oct 26, 2021 at 01:13 AM.
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2008 C350 Sport 4Matic Swap
Thermostats are common but not that fast. Try checking if its as simple as an air bubble in the cooling system. Open the coolant reservoir tank and squeeze the upper and lower radiator hoses a few times, if there's an air bubble, that should get it out.
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Thread Starter
MBWorld Fanatic!
Joined: Jun 2007
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From: Los Angeles, CA
2015 C400 Tenorite Gray
I squeezed the hose a few times but did not see any bubbles.
I have 145K miles. I think when I replaced it last was 80K-ish...
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2008 C350 Sport 4Matic Swap
Is there no heat at all? These usually fail in an open position or the seal in them fails so the engine takes longer to get to operating temperatures. If you're seeing low engine temperatures and no heat, its most definitely the thermostat.
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MBWorld Fanatic!
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From: Los Angeles, CA
2015 C400 Tenorite Gray
I took it in for an oil change a month ago. I presume the guy must have opened it to check the fluid.
I’m amazed how air gets in the system so easily.
I’ll try to bleed it some more. I remember waiting 2 hours before and took a couple of times..
i have not changed the coolant in 2 years…
Thanks for your help.
Last edited by Nicholi2007; Oct 26, 2021 at 01:13 AM.
Thread Starter
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From: Los Angeles, CA
2015 C400 Tenorite Gray
Had the same issue come up with the fan and erratic heat even after changing the thermostat again.
Changed the radiator cap.
Issues when away. Probably something I'll do on any car going forward once they hit 70K.
I can't believe I did not think of this before..
Changed the radiator cap.
Issues when away. Probably something I'll do on any car going forward once they hit 70K.
I can't believe I did not think of this before..
Super Member
Joined: Nov 2016
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2008 C350 Sport 4Matic Swap
Yeh these thermostats usually only last about 80-100k max on these cars. I went through 2 of them, original lasted to 80k, second one lasted a little longer but started being lazy in the cold at 180k.
Last edited by W204Motorsports; Apr 22, 2023 at 12:00 PM.
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From: Los Angeles, CA
2015 C400 Tenorite Gray
Not anywhere near as much power as the C350. Thermostat 1 was around 80K if memory serves correct.
I'm hoping to get into a C450. The C400 is tempting but the gearbox is not much to be desired. I hear mixed reviews about the C43 depending on year.
The heart says yes. The mind says stay in the car for 2 more years.
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From: Los Angeles, CA
2015 C400 Tenorite Gray
Ended up replacing the radiator cap as the seal looked questionable.
Issue went away. No more air and no more fan for take off sound! Sometimes it's the simple things.
Issue went away. No more air and no more fan for take off sound! Sometimes it's the simple things.
