W126 New Fan Blower & Motor: Is it DIY - and if so, HOW?
 

I just received a new fan blower & motor for my 350SD (from eBay seller Mercedes991) and I'm wondering if this is something I might be able to do myself. I have decided that the injector rebuild is out of my league, so I will be leaving that to a professional. Perhaps I can save a few $ by doing this job myself... what do you think?

I have attached a picture of the fan I received - would someone please confirm it is the right part first? Thanks!

From there, where do I begin to install it? I have been told it is behind the glove box liner - is that correct? If so, how do I get in there - are there any particular things to be careful of?

Thanks for the help! It will be nice to have my fan running again - especially since it's getting a little too cool to cruise around with the sunroof wide open all the time - high temps projected around 68F here in Las Vegas next week!!

I don't recall attacking the blower motor from the glove box in a W126.

IIRC the W126 blower comes off from under the dash. Pry off the right front door sill plate, remove the right front kick panel (1 screw, 2 clips?), remove the lower dash panel (3 screws along the dash edge and a quarter turn clip into the tranny tunnel?), remove blower casing lower cover (2 screws and 2 springy c-clamps), remove the electrical connectors to the motor, remove the 3 screws holding the blower motor and cage to the blower casing.

Sixto
93 300SD

Rusty -- I just pulled my blower motor out to do some maintainence on it. It's very easy.

According to my MB Service Manual CD, the procedure for our different year 126s is the same.

What I did was take out the three screws and one tab holding the cover underneath the glove box. Then there's a plastic shield that pops off. A few phillips screws hold the blower motor cover and a few more hold the fan assembly in.

You'll need a phillips screwdriver and a light of some kind. Might help to slide the passenger seat all the way back.

Wasn't too bad. A lot of dust and whatnot may fall out of the fan. Might want to put something down over the carpet.

That's all there is to it.

Good luck,
Bill

I have done this repair on my car and this procedure and Sixto's procedure are correct, the glove compartment does not need to be removed for access. I removed the motor to rebuild it and bench test it only to find the motor was good (although I rebuilt it anyhow) but the "porcupine" regulator that controls the fan was bad. So you may want to hook test leads to your battery and test the old motor once you get it out to make sure.

Thanks for the help guys - I'm planning to attempt it some evening soon (I have to wait until my wife is out - :rolleyes: - she has no faith that I can do this myself and is insisting that I take it to our mechanic, but I would rather save the money at this point since I have several other things I would like to have done that will require me to pay a mechanic - i.e. new Bosio nozzles & injector rebuilding) so I will see how it goes when I have the chance!:D

Hey Ched - when you found out the 'porcupine' regulator was bad instead of the fan motor, how much was a new regulator and how diffcult was that to replace? I'm hoping mine is just the motor - the symptom with mine was a gradual slow-down over the last 3 months. The fan was really strong when I got the car back in June, then it started slowing down, then it wouldn't start when I started the car - I had to 'thump' the dash under the glove box several times to make the fan start - and now even that doesn't really do anything. At this point, IF the fan starts turning (which it usually does not) it is VERY slow and doesn't do much except make an annoying noise. What do you think - does that sound like a bad motor?

Anyway, I'll get to it sometime very soon - like I said I just have to wait for the right opportunity!:D

Could not remove the carpeted cover under the glove box...
 

Well, my wife left about an hour ago, so I decided to give it a shot...

I removed the three screws and the clip, but I could not get the carpeted cover below the glove box to budge. I could pry the front of the cover away from the dash, but it was still obviously being held in place by something - I just don't know what. I got down on the floor and peered under the dash and I could not see anything else holding that cover in place. Is there some method to removing that cover that I don't know? I resisted the urge to force it - I certainly do not want to break something!

I also saw an unplugged plug on the left under the carpeted cover close to the center column - looked like perhaps something to do with the radio, like an antenna plug or something - looked a little like a small microphone plug... any ideas what that is? Sorry, I didn't get a photo of it - perhaps I'll try to snap one and post it in a little while (after my frustration fades a little!:D )

In re-reading the posts on this thread, I realized that I skipped the first two steps in Sixto's instructions. Is this the reason I cannot remove the lower dash panel? Is it supported by the kick panel?
Sorry - just trying to get it right so I can do this myself and save a few $ (leaving more to spend on new injectors, etc...:D )

The symptoms sound like the motor, probably the brushes which are replaceable. Mine was completely dead so the diagnosis was difficult. With yours, I would swap out the motors and see if that solves the problem, likely will. The regulator is bolted to the imprinted black motor cover, it will be obvious. I found one used on Ebay for $25. New is very expensive as I recall.

With the 3 screws out, is it loose at one end or the other? Are you able to pry it down enough to determine where it's still held to the dash?

I don't know for sure that it's supported by the kick panel. I'm pretty sure it is.

And maybe the duct that goes to the right dash vent is attached to the lower panel in a way that you have to tug it off. Hard to describe sufficient force in words.

As I recall there's a quarter turn fastener where the lower panel curves to meet the console. You might have found this in what you describe as a plug or socket.

Sixto
93 300SD

When I took out the three screws and the clip (the quarter turn fastener) I could pry the front of the carpeted panel down just enough to see behind it, but it was just flexing and not really moving away from the dash per se. I could not move it enough to see what was still holding it to the dash. I did notice an unplugged plug behind the left side - looked like something perhaps from the radio, but I'm not sure what it was. Anyway, it still seemed to be attached to the dash pretty solidly.

I was curious about the duct that goes to/from the door into that carpeted panel below the glove box - what the heck is that???

How do you go about prying off the door sill? I'm just concerned that I might break something - is it held on by clips or something? And where are the 2 screws and the clip that hold the kick panel?

It seems like it will be easy enough for me to replace the fan if I can just figure out how to get TO the darn thing! I guess that's the fun part, huh?!?!?:silly:

Mine wasn't, but our cars are almost ten years apart. I removed the kick panel first before realizing it didn't have to come off.

I think I had to pull on the panel a bit to get it off, but it wasn't too tight. It houses the duct which delivers air to the front doors.

Bill

If I remember correctly from last year, you should not have to remove the door sill or kick panel (at least I didn't) to get access to the fan cover. I did however, have to remove the passenger side floor mat because it extends so far up along the firewall that I seem to remember interference when dropping the carpeted panel. You may have to use a bit of force on the panel, it is a snug force fit.

My car does not have a glove box. Is the procedure the same?

Yes.

Sixto
87 300D

one more screw????
 

Hey guys....

I THINK there is one more screw in the panel......As I recall there are 3 screws along the front edge and then there is one screw sort of in the middle of the panel. I don't recall if that one screw just holds the 2 parts of the panel together or if it screws up into something.

Also, on mine you have to pull "down" on the front....then pull it out toward the seat to disengage it from the "back". It has some supports along the engine side that you might need to LIFT upwards to get them to disengage.

Hope this helps.

There are 3 screws at the top, the quarter-turn, plastic lock at the center console, and another screw on a small bracket protruding from the outside kick panel. There is also a screw in the middle, holding the two under-dash panels together. So that's 5 screws and a quarter-turn lock.

Once those panels are out, there are 4 screws holding the fan in place.

Pull the panel down slightly and then back towards you. It should pull out of the rear slots that hold it up. The sampler motor attached to the panel and there is a rubber hose that runs from the sampler to the display on top of the windshield. disconnect this hose. (It is a pain to get back on, but you can with patience.) You can either pull the sampler out of its clips or pull off the wires going to it. I have done it both ways and it is a little easier to reattach the hose with the sampler free of the panel. The sampler just pushes into the clips holding it in place.

When you are putting the new fan in place put the long phillips head screw you took out of the fan cover through the front screw hole and temporarily screw it into the air plenum. This will hold the fan in place while you screw in the fan attaching screws. Then back this screw out and install the fan cover. Make sure that the cover seals and that the fan wires are going out through the provided slot.

Before you tighten everything up, turn the key to the second position and make sure that both the blower and sampler fans work. Put the blower on high, auto and low to make sure it spins at all speeds.

When you install the panel, first slide it in and line up the air passage in the panel with the air duct coming from the center console. Then stick the panel into the slots at the rear (firewall side) hook up that darned sampler hose then carefully line up the three screws in the front. You will probably needd a small flat bladed screwdriver to manipulate the metal clips the screws go into.

This should all take you under an hour.

Good luck!

Thanks for all the input.

O.K i I got to the blower motor as per all of your info. I pulled the two wires off the motor an put 12 volts to the motor and it works great.With the key on,i am getting power from the two wires the go to the motor.I am confused.

Blower motor control is kinda counterintuitive. The blower gets constant +12V through one wire and varying voltage through the other - high voltage for low fan speed and low voltage for high fan speed. IIRC the contoller puts out close to 0V at max and something like +11V for min. Roll the temp wheel with the blower set to auto to check intermediate voltage noting that the controller responds slowly to changes.

You can also check upstream of the controller. That's more straightforward. IIRC the controller sees from the PBU 0V or close to it at min and 7V(?) at max.

When supplying power directly to the motor, set it at the same orientation as it is when installed - pointing up. This orientation puts the greatest load on the bearings. Many motors that won't work when installed test perfectly fine horizontally. If you can move the shaft along the axis of rotation, get a new motor or get some new bearings installed.

Sixto
87 300D

I never took the BM out of the car as you can see in the picture.The voltage remains the same when rolling the wheel.Also the monovalve hums until i roll it down[on blue] until it clicks on max,then it stops.

Does the monovalve have anything to do with the Blower Motor coming on?

Nope. Unrelated circuits downstream of the PBU. Neither monovalve nor blower has electrical feedback to the PBU. The most they can do is blow the system fuse.

Sixto
87 300D

I know nothing about electrical stuff,so what do you think is the problem?

Let me see if I can explain what you are seeing on the meter. In automatic mode there will be voltage on both. One should be +12v (batt.) and the other should vary (0-11v) realizing that 0-to-11 is more "negative" than 12. Showing 12volts on both pins means there is no difference between the them and no current flow. (Think along the terms of water pressure.)

Have you tried the fan in Hi/Lo vs. Automatic?

If the blower will not work in Hi, Low or Auto, and since it spins fine when connected to the battery, I would check the pushbutton controller. It gets more mechanical wear and they are notorious for intermittent solder cracks at the points where the circuit boards join. Do a search of "resoldering" and you should find pics. It is a pretty simple repair but if needed, find a buddy that can touch it up for you.

The "humming" of the monovalve tends to point to the temp. controller but the pushbutton controller turns it on. Since you are getting a semblance of control by varying the temp wheel, I am thinking it should be working.

Answer:
 

The blower regulator is bad.
Fastlane:
http://catalog.peachparts.com/item.wws?sku=W0133-1598146


The regulator controls the blower ground = regulates power through ground for speeds.

No ground = no motor speeds.




Have a great day.

At this point, Roy, I don't think the data is available to confirm whether it's the blower regulator or the CCU.

Answer
 

That is the (failure prone) porcupine regulator, not the earlier triple coil resistor unit.
If anyone local has a spare, I suggest you borrow it for diagnosis, and buy it if needed, it would save serious money.

Agreed, but I'd hate to pay that kind of money just to find out that the CCU isn't providing the voltage to the porcupine.

I'm going to buy one of them on e-bay as a spare...........just for such a situation............it's very difficult to confirm whether it's the CCU or the porcupine.

Something got into my blower motor...
 

My blower motor started becoming noisy about 6 months ago. Finally got to the point where I decided to do something about it. Found a used W126 unit on Fleabay for $50, so I decided to attempt the repair myself based on the information above. (By the way, thanks guys!!) When I removed the old unit, look at the pictures to see what I found::eek::eek:

I haven't a clue what the mess is. There are no bodies or dead bones mixed in, so I figure it's not of the animal variety.

Anybody ever seen something that looks like this before?

I popped the new unit in, and it works like a charm, but I didn't know things like this "grew" in blower motors...;)

I hesitate to reply as the post is so old but to get to the HVAC motor on the 350SDL (1991) take off the under dash carpet and the sidewall panel on passenger side. There on the right side about 3 inches up you will see a black pipe and the motor in a flexible aluminum holder wrapped in foam. Unplug from the rear and replace. No need to take out glove box or vents as they will not help you get to this little PITA.