Climate control - pulse at highest fan speed
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Junior Member
Joined: Jul 2013
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2000 E320W 4Matic
Climate control - pulse at highest fan speed
I've noticed something new, and wondering if it's a vacuum issue. It's getting hot here in the Southeast US. Last week, driving out of an open parking lot in full sun, my car was blazing hot (black-on-black E320). I had the climate control set to "auto" and some reasonable temp (probably 70F). I noticed that the fan speed was pulsing. It would come on full blast for about a second, then back down to a lower speed - still showing the highest fan speed on the display. A few seconds at that speed, then it would pulse back up, over and over. If I manually set the speed down to the second-highest setting, the pulsing stopped.
The only other issue I've had with the climate control is something I suspect is a sensor. Setting the temperature isn't predictable, especially in cold weather. I sometimes have to turn it up to the mid-70's (F) to get any heat at all (even if the outside temp is in the 'teens). Then I have to turn it back down to some reasonable temperature (low 60's perhaps) after it starts to warm up, to keep from baking. I can't think of how these would be related, unless the entire climate control module is shot.
The only other issue I've had with the climate control is something I suspect is a sensor. Setting the temperature isn't predictable, especially in cold weather. I sometimes have to turn it up to the mid-70's (F) to get any heat at all (even if the outside temp is in the 'teens). Then I have to turn it back down to some reasonable temperature (low 60's perhaps) after it starts to warm up, to keep from baking. I can't think of how these would be related, unless the entire climate control module is shot.
Thread Starter
Junior Member
Joined: Jul 2013
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2000 E320W 4Matic
Thanks, I'll have to look into what that would take to replace. Might not be too bad.
I haven't tested the duovalve. I'll have to look that up. The coolant gauge does appear to work properly - it shows temperatures you'd expect as the engine warms up, etc.
Regarding the heating, does your coolant gauge work properly and have you ever tested the duovalve(does it respond to voltage)
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Joined: Jan 2009
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From: V E G A S
1922 Ford Model T / no OBD
Do the test like suggested in http://www.mercedesmedic.com/ac-air-...le-codes-list/
Also next time, observe fan speed on display.
Very often computer diverts the air to different ducts and owner take different sound as speed change.
Also next time, observe fan speed on display.
Very often computer diverts the air to different ducts and owner take different sound as speed change.
Thread Starter
Junior Member
Joined: Jul 2013
Posts: 71
Likes: 1
2000 E320W 4Matic
Do the test like suggested in http://www.mercedesmedic.com/ac-air-...le-codes-list/
Also next time, observe fan speed on display.
Very often computer diverts the air to different ducts and owner take different sound as speed change.
Also next time, observe fan speed on display.
Very often computer diverts the air to different ducts and owner take different sound as speed change.
The speed doesn't vary on the display, but if I manually lower it one stop (sometimes 2), it very clearly doesn't pulse, so it's a speed change.
Member
Joined: Nov 2013
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2001 Clk55 AMG
I had a similar problem with my clk55 last year, and in my case it was a vacuum leak at the reservoir inside the right front fender. There was a cracked fitting where that grey plastic hose connects. This would let the vacuum bleed off and the center vent flap would close, this feels like the fan slowing down to you inside of car. I first replaced the fan controller, but that did not change the symptoms.
Thread Starter
Junior Member
Joined: Jul 2013
Posts: 71
Likes: 1
2000 E320W 4Matic
I had a similar problem with my clk55 last year, and in my case it was a vacuum leak at the reservoir inside the right front fender. There was a cracked fitting where that grey plastic hose connects. This would let the vacuum bleed off and the center vent flap would close, this feels like the fan slowing down to you inside of car. I first replaced the fan controller, but that did not change the symptoms.
