300CD Noisy Climate Control Fan - PeachParts Mercedes-Benz Forum

Gil · #1 08-20-2006, 02:13 AM

OK, there may not be anything I or anyone else can do about this, but my 300CD is probably like most other 123 cars - the heat/climate control/ac fan makes a lot of noise during normal operation but doesn't seem to blow out a lot of air. I know the two center vents aren't supposed to do much (which always seemed silly to me), but the entire system seems to be a bit lame - lots of noise but not much output. Granted, I'm comparing this to newer cars which seem to have much quieter systems and blow out as much or more air.

Is this because the fan motors are old in these cars, or were they always that way and is it just the design of the climate control system that makes it sound and perform like an electrolux with a pacemaker? Has anyone replaced a fan motor to notice any difference?

#2 08-20-2006, 07:59 AM

It's not clear from your description exactly what's going on. If the CCU and vacuum pods are working correctly, you will get about the same amount of air from the center vents as the side vents. Are you saying the center vents do not provide good flow in AC mode?

The blower does make some noise in high speed, but not a lot. The blower motor can make squeaky noises if the bearings are worn. I've replaced my motor to get rid of the noise and to make sure the high current didn't damage my CCU. The sound from the blower isn't usually noticeable with the engine running. How does your car's blower compare to other 300D/CD?

Gil · #3 08-20-2006, 10:05 AM

You got it - the center vents to diddly squat in AC or any other mode. In another post, someone said this was how MB designed the car, though that never sounded right. The flow is good from underneath and on the side vents, and also the defrost vents. The CCU has been replaced with a rebuilt unit from Programa a few years back, and seems to do what it's supposed to do, with the exception of the temperature wheel - it needs to be all the way in the cold position for the AC to work (that's a different problem, though).

The entire system makes plenty of noise, but not much flow. Nothing squealing or grinding or anything like that, the motor works but just makes more wind noise than I thought would be normal. I have yet to listen to another 300D or CD for comparison, though, so I'm not sure if this is just how the cars are or what. Modern cars are much quieter even at max fan settings, so I'm wondering what the differences are and if swapping out the motor would help. Thoughts?

tangofox007 · #4 08-20-2006, 10:34 AM

Quote:

Originally Posted by Gil

the center vents to diddly squat in AC or any other mode. In another post, someone said this was how MB designed the car, though that never sounded right.

The value of free advice often equals its cost.

Gil · #5 08-20-2006, 10:45 AM

So that's true, then? The center vents aren't supposed to do much of anything? Seems pretty pointless.

tangofox007 · #6 08-20-2006, 10:50 AM

Quote:

Originally Posted by Gil

So that's true, then? The center vents aren't supposed to do much of anything? Seems pretty pointless.

No, the output of the center vents should be about the same as the side vents. (The center vents might even blow stronger than the side vents as they are "upstream" from the heater core.) Your center vents are not individually turned off, are they? Can you see the center flap move through the center vents when changing from heat to a/c?

Gil · #7 08-20-2006, 11:12 AM

I checked the individual vent controls, but they work fine. Not much output when open. Haven't gotten underneath to see if the hoses are messed up or whatever, but what are the chances of both being out? The car was in great shape from the original owner when I bought it - I don't think he messed with anything up in there, but I'll look. Is the center flap visible from the vent or from somewhere under the dash? I still think the fan itself makes way too much noise.

tangofox007 · #8 08-20-2006, 11:16 AM

Quote:

Originally Posted by Gil

Is the center flap visible from the vent or from somewhere under the dash?

Look through the center vents.

Gil · #9 08-22-2006, 11:10 PM

OK, you were right - I went out and looked inside the dash with a flashlight, just for laughs, and sure enough the vent to the center dash holes is closed - has probably been that way since I bought the car. The replacement CCU unit from Programa was never enough to open the vent - maybe a vacuum leak somewhere? Not sure what to tear apart next - any suggestions? Thanks.

JimmyL · #10 08-22-2006, 11:44 PM

As you are coming to realize, the center vents are not for ornamental purposes!

My hardest air output comes from those vents. Probably the CCU is not necessarily to blame. It is usually due to a vacuum leak somewhere, often the center vent pod (yes, the hardest one to get to). There is much info to search for for the vac leaks, and also for the manual propping open of the center vent to allow airflow through there.
The loud fan could be a separate issue. Do you mean loud as in sounding like it's flying apart, squeaking, or just blowing allot of air?

Gil · #11 08-22-2006, 11:59 PM

...the whole system just makes a ton of wind noise - maybe won't be so bad with the center vents open, but just seems like newer cars with different sytems don't have this problem. When you have to turn the radio up considerably to overcome the rush sound of air, then something ain't right - especially when the air flow isn't great - the center vents being shut may be the problem. Thanks for the tip about the vacuum pod. FIGURES it's the hardest one to get at!

Have to try propping it open in the meantime.