Can anyone advise me on what fan is switching on and off whislt the car is running. On start up, I hear a fan from behind the dash. It sounds like a vacuum cleaner and appears to be 2 fans starting one after the other. After driving for a while and then stopping at, say traffic lights, I can hear the fan start up again and then go off after about 30 seconds. This continues but can't be heard whilst driving due to road noise. The Air con is set to auto and 21C on both sides and the fan blower runs normally in-line with the fan settings on the dash. Everthing is working normally, but I just want to understand what this fan is. I wondered if it was the fans that run to blow exhaust gases through the cats on warm up or if it's the air con turning on and off as the outside temp is around or below 4C and I understand the air con switches off at tepmps below 4C. Any help would be gratefully appreciated. Matt
unidentified fan on R230
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What year is your car Matt, does you car have the red and blue press buttons just above the vent thumb wheels
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Malcolm, Happy New Year.
Mine is an 05 car built in 04. It doesn't have the red and blue buttons - it has the same climate control as the new cars. Hope that helps. I took it in to ask but they said nothing was wrong, which I believe, but they couldn't hear the fan as there was too much noise in the workshop. I can hear it all the time at idle.
Mine is an 05 car built in 04. It doesn't have the red and blue buttons - it has the same climate control as the new cars. Hope that helps. I took it in to ask but they said nothing was wrong, which I believe, but they couldn't hear the fan as there was too much noise in the workshop. I can hear it all the time at idle.
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Same to you Matt,, the only fan under the dash is the one built into the Comand, this can stop and start at any time, even when off, and going to sleep.
There could be a unit smack in the middle of the engine, an air pump that can run, not all cars have them.
http://www.detali.ru/cat/oem_mb2.as...GM=717.433&CT=F&cat=15U&SID=72&SGR=045&SGN=03
There could be a unit smack in the middle of the engine, an air pump that can run, not all cars have them.
http://www.detali.ru/cat/oem_mb2.as...GM=717.433&CT=F&cat=15U&SID=72&SGR=045&SGN=03
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do you mean the aux air pump??
If so, what does it do and is it normal to run on and off or has a sensor failed?
Garage didn't mention it but I see it on the diagram as part 5 in the manifold.
If so, what does it do and is it normal to run on and off or has a sensor failed?
Garage didn't mention it but I see it on the diagram as part 5 in the manifold.
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I will take a further look in WIS. strange thig is that I though I had a fan noise last week when out, but nothing today.
My mind is blank on the aux pump,,we have have a post before on it,,see what I can find. there are no fans of pumps under the dash, only the main heater one
My mind is blank on the aux pump,,we have have a post before on it,,see what I can find. there are no fans of pumps under the dash, only the main heater one
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I have sent you a paper with some info on this,,maybe of some use.
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Could it be the pump 140 running during this cold spell,,I do not use my car everyday, but I did notice something running last week on my car
http://www.detali.ru/cat/oem_mb2.as...GA=722.633&CT=F&cat=65P&SID=83&SGR=180&SGN=05
http://www.detali.ru/cat/oem_mb2.as...GA=722.633&CT=F&cat=65P&SID=83&SGR=180&SGN=05
BlackC55
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Does it whistle like a high pitched fan?
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I know I'm not explaining it very well, but it sounds a bit like my old supercharger. Its like a fast turbo type fan and is very obvious when you turn the car off with the door open; you can hear it running down. My concern is that the fan is turning on and off like a sensor has failed and it doesn't know whether to be on or off. It's not in the cabin as I can hear the heater blower separately. It's not the radiator cooling fan. It's like a pump that runs when the car is stopped and at idle although as I said I can't hear it over road noise so I'm not sure if its doing it all the time. By the way, the engine running temp is constant at 90C and the climate is working normally. I can make the unknown fan turn off by selecting 0 on the climate; and turn it back on by selecting the climate back on, that's why I wondered if it was something to do with cold conditions and the car not freezing up the air conditioner.
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I am aware of this noise, as I said before, mine did this last week, and I turned off the internal heating fan to listen.
I am going down to my car and lift the engine cover off, and have a nose around
I am going down to my car and lift the engine cover off, and have a nose around
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Just reading this I was curious - I have a 2000 W210 with Comand, and every time I get in the car I hear a small turbine/fan sound. Always wondered what it was, but if Comand has an inbuilt fan.....
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The Comand does have a fan, and on cars with go to sleep circuits it can run for 20 mins after you have turned off and locked up,, I think that the 210 also has a tiny one in the OCP
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Yes, I get this too as do all Comand owners. The Comand fan if very quiet. My unknown noise only occurs when the engine is running and is a deeper sound from the engine bay somewhere. When I start the car I hear 2 fans/pumps start up. My car has fans that during cold start blow exhaust through the cats to help warm the cats up faster. If one of these is still running when the car is warm then something is wrong. Most probably it's just some clever aux pump trying to circulate water or something.
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I have just been out and removed all of the covers, and left the engine running, the Aux fan came on once for a very short burst (turbine sounding, and quite loud) there are no other motorized components on the car. This aux fan I will read up on later in the day
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so I'm not going mad! Thanks for your test, all I would like to know is what it's doing and why. Could it be somthing that just runs in colder weather? I bet it's simple - I am. 
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so I'm not going mad! Thanks for your test, all I would like to know is what it's doing and why. Could it be somthing that just runs in colder weather? I bet it's simple - I am.
By its description and where the pump is joined into the manifold,it is only required to run in certain conditions, as I said I will read up on it tonight
