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late 2009 CLK 350 Coupe Elegance, '65 Jaguar S Type wires
I suspect that omission of the Aux coolant pump for whatever reason is the likely cause of this condition. Benz has been fitting Aux pumps to the heater system forever. I can't imagine why they deleted them from some US W204's. I can only believe this was an ill advised cost cutting measure to meet sticker price targets.
Just giving my 2cents bump to this thread, my w203 had minimal heat at idle until I replaced my leaking (badly) aux pump, now it's got great heat at all conditions. I found this thread looking for a solution to a similar (though not as bad) low heat at idle problem in my wife's R350, and when I finally get off this couch I'm going to go look to see if the aux pump is there on her car.
This is from a US 2012 C350. I believe that I have an auxiliary coolant pump. Can anyone confirm?
When I'm in idle, the heater cools down substantially to the point where cool air is blowing through the vents. It only gets warm when the car is in motion. Weather is ~5 degrees F.
This is from a US 2012 C350. I believe that I have an auxiliary coolant pump. Can anyone confirm?
When I'm in idle, the heater cools down substantially to the point where cool air is blowing through the vents. It only gets warm when the car is in motion. Weather is ~5 degrees F.
Yes, you do have the pump. Now you just blew my theory about adding it to my 09 C350 to add some much needed heat at idle Has your car always been cold at idle, or did it just start recently?
I've had the same problem on my 2010 C300 and just replaced the thermostat and housing ... Which is the only way to do it and fixed my issue ... Heat blows hot now ... Hope this helps .. I live in Missouri to where it's been really cold lately
I've had the same problem on my 2010 C300 and just replaced the thermostat and housing ... Which is the only way to do it and fixed my issue ... Heat blows hot now ... Hope this helps .. I live in Missouri to where it's been really cold lately
Good to know. Temps are very cold out here in Alaska as well. Replaying the t-stat tomorrow. *cross fingers* hope this corrects the issue.
2025 AMG E 53; 2018 GLC300 4Matic; 2003 360 Modena
To clarify from my 2010 C300 example ... during warm-up - the car would lose heat while idling. On very cold days, 10 degrees F, HVAC in Auto Mode (A/C deactivated, not that it matters), the engine warmed up as usual and the heater fan would begin to activate as the coolant temperature began to reach the ability to produce heat. Within a mile or two from my house - there is a rather long stoplight that if I caught it, the heat would would slowly start to turn cool and by the time the light turned green would basically be cold air. Within about 10 seconds of leaving the light and driving - the heat would return. Once the car reached a solid operating temperature (not necessarily full operating temperature), this would no longer happen. Meaning, at idle, full heat was being maintained.
This supports Glyn's theory, and to me, is perfectly normal operation for a car without the Aux pump. I bet the C300s didn't have them and the C350s did/do. My '06 E350 has the pump and the above doesn't happen.
I don't think that this operational characteristic is abnormal for a car without the pump, only with the pump.
My 2012 C350 blows luke warm/nearly cold air at idle. I complained from day 1 and they said "that's normal because the rpms are down.) I explained that every car I've ever owned...cheap/used American cars NEVER had that problem...and I'm quite aware how heat works in car. They tested and still claimed that that's "normal". Probably the only thing about the car that bugs me to this day.....
My 2012 C350 blows luke warm/nearly cold air at idle. I complained from day 1 and they said "that's normal because the rpms are down.) I explained that every car I've ever owned...cheap/used American cars NEVER had that problem...and I'm quite aware how heat works in car. They tested and still claimed that that's "normal". Probably the only thing about the car that bugs me to this day.....
I have a 2000 Honda Civic I use as a winter beater and that thing blows heat so hot it will make me sick. No aux heat pump or any of that nonsense fitted.
My old 1985 VW Golf I had back in the mid 90's blew crazy heat also. It confuses me why a $40,000 car won't blow hot all the time.
My 2012 C350 blows luke warm/nearly cold air at idle. I complained from day 1 and they said "that's normal because the rpms are down.) I explained that every car I've ever owned...cheap/used American cars NEVER had that problem...and I'm quite aware how heat works in car. They tested and still claimed that that's "normal". Probably the only thing about the car that bugs me to this day.....
I have a 2012 C350 too that exhibited cool air at idle. First they replaced the thermostat. They claimed it fixed the problem, but it still occurred. Next they found out the front sam had the wrong software they caused the auxiliary coolant pump to stop working. The pump itself was still working, as they tested it with direct voltage. They updated the software of the front sam, and now I am getting warm air at idle.
Hmmmm....wondering if it is designed to limit heat to the passenger compartment to get the engine up to operating temp sooner at idle.
I have the same problem but never happened last year, just now as we have come out of summer turned Dail to warm again & noticed this, I have just finished trying to bleed off any air by running engine with header tank lid off for approx 1 Hr engine gets up to about 85-90 c without issue Dail turned all the way hot no a/c or circ all off just manual when above 2000 rpm gets super hot as soon as I lift off to idle air gets coldish pretty quick mine has no aux pump as standard, I was thinking maybe t stat could be stuck slightly open & when revs high water pressure forcing it open more so air gets hot then at idle pressure drops allowing t stat to close again causing water heat to drop off hence air getting cool, is this possible or thesable..??
I have a c250 coupe and I got thermostat replaced belt replaced idle pully replaced leak fixed and still have no heat when the car is on battery light comes on got battery checked everything is good and it’s 27 degrees and I’m in Ohio by the way. If anyone can help I would really appreciate it.
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Has your car always been cold at idle, or did it just start recently?
