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I have a 1995 E320. My fans seem to work fine. At least there is plenty of noise that sounds like the fans should be blowing air. I get the best flow from the side vents and I can feel that the air is warm, but there is just very little flow from the defroster and the floor vents. Even on high and with the controls set to all defroster, I don’t get much flow from the defroster at the windshield. I tried every possible setting for auto, max and low speed fan, as well as the different settings for all defrost, half and half defrost and floor, and mostly floor.

Let me see, I also have a rather loud slapping sound from something closing in the dash when I start the motor in the cold. I have had that for quite a while, even before I noticed the loss of the flow of air. I figured that was a fresh air supply vent slapping closed that limited outside air until the car warmed up a bit and maybe some foam padding had deteriorated. I did have decent air-flow in the past, even when I had the loud slapping.

Anyway, please help me understand what might be causing me to have low air flow from defroster and floor vents, even though I have a fan that sounds like it is blowing and the air seems to be warm. This is not a good situation going into a Pennsylvania winter. I just spent $1200.00 to get my front spring perches re-welded onto the car this week, so this is not a welcome surprise.

Thank you everyone,

Ken
 

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Ken,

Sounds like your main air vent isn't opening as it should. It is located up above your fan motor mount. If you have ever changed the blower motor, it is the large flap above it. Check the vacuum lines at the three prong connector behind the power brake booster as well (yellow in color). Go to mercedesshop.com and click the "resourse" tab on the home page. In the drop down menu, you'll find a DYI section. Inside that section is found step by step instructions for changing the blower motor. All of the steps listed (except removing the blower motor) are needed to get to the vent door. It isn't a hard job, requires only a 10MM socket and phillips head screw driver for tools and should take you about 2 - 3 hours to do or less. Depends on your DYI skill level.

Let us know what you find and good luck,

Jayare
 

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Discussion Starter #3
Thanks for the tip. I have seen the DIY for the blower motor. It would be great if the flow could be improved without pulling the dash by simply fixing something with the main vent.

For the record, I also got a tip about checking the filters to be sure they are not clogged. My late model W124 has cabin filters and it turns out they can get clogged. The filters are under the wipers too, so going after them will lead to the main vent as you suggested. I also have had a squeaky fan for quite a while. It is intermittent, but this may be the time to fix that too.

I guess it makes sense to do everything possible from the motor side, before I think about going into the dash.
 

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You'll have to go through the same R/R process to change the cabin filters. My 400E doesn't have the filter system, but you very well may have a set that are too clogged to allow correct airflow. When was the last time they were changed if ever? It really isn't that daunting of a task to do. 90% of all the parts that need to come off are held in place by clips. Print off the DYI article and start studying what you have to do. It makes clear sence once you get started.

Good Luck

Jayare
 

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Discussion Starter #5
Ken,

Sounds like your main air vent isn't opening as it should. It is located up above your fan motor mount. If you have ever changed the blower motor, it is the large flap above it.

Jayare
Hi Jayare,

Today I tried the re-circulation switch and it seemed to make a difference. When I went back to no re-circulation, it seemed like I was still getting the better flow from the floor vent and the defroster. If the re-circulation switch temporarily solved the problem, does that give you a better idea that the underlying problem might be the main air vent? To me, it seems the main vent might be something that is controlled by the re-circulation switch.

If that turns out to be the main vent, then you will be the one to have properly diagnosed my problem. It would also be much better than having to do the pods, since it is accessible from the motor side. That is of course only if the problem with the main vent isn't still a pod thing that is under the dash. If I do have a problem with the main vent, is it likely to be something that can be fixed from the wiper side. I am only saying this because I can imagine a situation where the flap is accessible, but the controls for the flap are not accessible without going into the dash.

Thanks again for your help,

Ken
 

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please forgive me Im new and dont know how to start a new thread. I have a 1993 400E and my heater blower moter is not blowing. I replaced the panel withg the switches but the same thing. Any ideas. Any ideas on the blower motors in these units?
 

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please forgive me Im new and dont know how to start a new thread. I have a 1993 400E and my heater blower moter is not blowing. I replaced the panel withg the switches but the same thing. Any ideas. Any ideas on the blower motors in these units?
Forgiven if you fill out your profile. Click on the gray "new topic" link at the top of the list of threads on the w124 forum main page.
 

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Discussion Starter #8

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Ken,

I am leaning towards your cabin filters being the problem. When you engage the re-circulation function, outside air intake is eliminated from the equation for approx. 20 - 30 min. After that period, the system will de-activate itself, much like the rear window defrost. With outside air intake being eliminated, so are the outside filters and airflow volume will increase. The cabin filters are charcoal impregnated and if it's been a "few" years since they have been changed, then ............

I had a very similar problem with my wife's Olds Aurora a few years ago. Quite frankly, I didn't ever pay that much attention to the HVAC system and certainly didn't realize it had cabin filters. I could hear the roar of the blower, but there was only a trickle of air making it out of any vent or defrost. I keep a spare filter for her car now.

Litigator - Your car has two fuses for the blower motor. One is located inside the fuse box (#7) and the second is a 30 amp. "strip" fuse located just ahead of the fuse box. Attached pictures show it. Check both fuses. Chances are, the strip fuse has taken a hike.

Good Luck

Jayare
 

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Discussion Starter #10
Heated air temperature?

I just drove home from work in car and played with all of the settings quite a bit. I don’t think my airflow is great, although it seems better than last night and since I played with the recirculation switch.

Now, however, I am wondering if the real problem is that the temperature of the air isn’t as hot as it was in the past. Could my air temperature decrease? If so, what would cause the problem? I think I have read things about heater cores going bad. I will have to do some searching on that, but I thought it wouldn’t hurt to ask.

I can also test the temperature coming from a vent, like I have done for the AC. Do you know what temperature the heated air should be coming out of the vents?
 

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Heated air will never exceed the temperature of the engine. If the heater core was bad, coolent would be leaking into the car interior. Like the A/C evaporator, it is a major task to change out. The mono valve controls flow of engine coolent into the heater core. It is located on passenger side of the engine compartment to the inside of the right strut tower (pic attached). However, I'll still lay odds that your cabin filters are the culprit.

Good Luck,

Jayare
 

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Thank you Jayare for the great pictures and support. I will do the filters and hope that my problems are solved.

Thanks again,

Ken
 

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My blower regulator (the solid state device living under the blower) dropped too much current and allowed the motor run at high and low but slower than normal. What I felt at the vents was wimpy air flow but could hear the blower whirring.

I removed the filters, while cowl diving to replace the regulator and never put them back thinking more air-flow would be a bonus. The result is crazy, the thing on high with the center vents on A/C will literally blow your hair back. The output may be too much for some but I like it, less load on the motor. Filters are for girls. (kidding)

The heater core may be internally calcified blocking flow. If the coolant is up to temp, a restricted core may flow to where the blower cools hot water creeping through it too quickly resulting in luke-warm vent output. Chemical radiator flushing might break it loose. There may be a method to "back-flush" the core with a basic garden hose and some adapters. I've had a couple cars that this cured the wimpy-heat deal.
 

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+1 to what WhiteKnuckles just said. I think what Ken may have been getting at is the possibility that his heater core is blocked, not that it might be leaking.
That said, Ken, what is the reading on your temp gauge? Another thing to consider is the possibility that your thermostat could be sticking open a little bit causing coolant to circulate through the radiator when it doesn't need to. This will consequently lower your engine running temp, and as you already noted if the temp is not up the climate control won't tell those fans to spin. But, since you said that it sounds like the fans are making plenty of noise and just not sending a lot of air I would look for some constriction.
So, I think you guys are on the right track with checking the cabin filter. I'm interested to hear how this turns out.

Also, am I correct that the cabin filter is a later feature for the W124? Does my 1988 300E have one, or no?
 
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