W124 blower motor advice sought

[MB250TD]

It is that time of year when problems with heater blower motors regularly get posted! I have searched old posts and realise the problem I have is common in enough in W124s (mine is a 1996 E300TD). The blower motors has been erratic, coming on some time after beginning a journey, and sometimes failing to come on at all. The blower has now stopped all together, although a slow current of hot air will still come through the vents while driving. The blower motor in my car was replaced in 2004 by the previous owner and so the current unit should not really be failing. There are some excellent guides to removing the blower motor eg: (http://www.mercedesshop.com/Wikka/W124BlowerMotor/show?time=2006-08-14+13:38:32)
but the job is quite a big one, involving removal of the wiper motor first, though relatively logical and requiring no special tools. I am prepared to have ago to save labour rates, but a new blower motor and the squirrel cages around the fans are expensive - too expensive to order one and have it ready should a failed motor be the problem. The usual problem seems to be worn brushes and a dirty commutator, and from all accounts, the chances of getting the motor going again after removal and a clean seem good. Other than the obvious (blower motor unplugged at bulkhead behind dash - observable under bonnet just above fuse box) or a blown or misalingned fuse (Fuse no 12 apparently can get hot and the contacts deform), the only other problem seems to be a failed regulator. Obviously I do not want to do the job twice, but without somewhere dry, I do not want to leave the car dissassembled should I have to order new parts and wait for them to arrive. I would be interested to hear how other people have got on with this repair, or whether they have left it to the experts? Is there a good success rate in getting the blower motor going again, if so, has anyone any advice / tips?
Thanks
John

 

[Ardveen1]

Mercedes W124 Facelift Heater Blower Motor

Hi, I recently picked up a W124 Coupe 1994 model, in very good condition but with a few problems, it was a non runner. I stripped the scorpion alarm out and reconnected the starter motor and fuel pump. The car still would not run and with the help of forums I ended up checking the OVP and sure enough it was the culprit, sourced one on ebay, fitted it and the car fired up and has not looked back since. The heater blower was also not working at all so tackled this next, it is a facelift W124 Coupe and a bit different than some of the forum guides which are for the earlier 124 I think. The procedure I used ( not a mechanic ) was
Remove the Aerial as well discussed previously, very tight and i over strained the slot for the allen screw but it still goes back in and holds the wiper arm
Rermove the wiper arm and lift the bonnet vertically by pulling back the restrictor clips either side.
Remove the rubber seal at bottom of windscreen, it just clips in and mine was too loose to actually clamp in to the plastic grooves, another reason to tackle the job was that I thought I could repair this on re-installation. The plastic is one piece across the entire window so pull it to the centre each side, it will not remove as it is engaged to the wiper motor.
The gutters are directly below the rubber seal pulled back as above. Their fixings to the bulkhead are visible, philips screws and a white pull back clip underneath. They also engage with the drains either end so must be lifted out to release, When unfixed they simply pull away, one either side, so two pieces in total.
The remaining centre section is held to the firewall with two plastic large screws which can be hand loosened and pulled back, it is also screwed, philips, to the bulkhead
Remove the wiper mechanism by unbolting, 4 x 10 mm bolts - 2 on the bulkhead and 2 slide out ones visible from above. Unplug the wiring pin connector and remove the wiper mechanism from the car.
The fan now is visible in the centre house inside a large round drum, held in by 3 bolts, 8 mnm I think, there are to wires, one with male end, other has female end so they cannot be mixed up on refitting, remove them and take out the blower motor.
The blower motor comes out with its plastic housing and squirrell cage, mine was a single cage, not the double I have seen on some forums.
I blaster the motor with an air gun to blow away ant dust ( put mask on )
I removed the plastic housing by removing the single screw on top and prising between plastic case and motor with a screwdriver, its a tight fit but comes apart.
Now I had the motor in my hands and connected it to a battery, i connected red to positive and brown to earth - nothing happened - dead.
I noticed alot of carbon on the rotor and deiced to clean it.
The brush housings, 2 number, are clearly visible, I bend back the top edges to release the springs which push the brushes against the rotor and removed the springs.
The brushes appeared to me to have a fair bit of meat leaft on them, at least 15 mm on each, I figured on retaining and cleaning them.
The brushes have not enough wire to allow them slide out of the housing with with the springs gone they can slide up and down in thier housings.
I cut some fine grit sandpaper into approx 12 mm strips and fed them in under the brush contacts with the rotor, pusherr down the brusher againt the sandpaper and pulled the sandpaper against the brush contact faces, did this quite a few times on each and removed alot of grit from the carbon brusher face.
Next I reversed the sandpaper and prised it against the rotor and twisted the squirrell cage to rotate the rotor, again did this quite a few times until the rotor was shiny and clean. Next I dipped the sandpaper in white spirits and repeated the cleaning on both rotors and brush fases and finally blasted again with compressed air.
Next I reconnected the motor to the battery and i kicked off spinning, quite a jump with it rums so well advised to clamp the motor before powering up. It was running like new, just carbon build up was breaking the electrical contact beforehand.
Reassembly is the reverse
Refit blower motor into round housing and secure with 3 bolts, reconnect male / female wires.
Rebolt wire mechanism, 4 bolts as before, reconnect wiring block pins, apply some grease to stainless steel wiper push rod.
Reconnect centre section of plastic housing, philips to bulkhead and plastic screws to firewall, try to prise in the centre rubber sealing apron into the slots in the plastic - messy job to get right - not very successful in my case.
Refix the gutters either side ensuring they engage with the drain piper, reengage the white plastic clips under joint where side section meets the centre section, refix philips screws to secure either gutter to bulkhead.
Fold back and Press down carefully rubber windscreen seal and fix into plastic channel below windscreen and separate one along gutter edge, clearly visible when rubber lifted back.
I could not get enough friction to retain the rubber seal in the plastic channel below the windscreen so ended up using black ducttape and allowing to over run by approx 1 inch onto the windscreen to seal and allow rain run into the gutters and away.
If rain is getting in behinf this seal it could possible mess with some of the electrics particularly the ECU / OVP / Fuel Pump Module which by the way were not protected by the plastic cover in my case. I picked up a cover from a breakers and fitted it, and to be sure I further fitted another piece of plastic above this to make sure everything drains away from the electrics ( in case the duct tape fails )
Refix the wiper arm and bolt in the allen nut together with broken piece of metal from the casing, it all held up securely and as push rod is slotted to receive the allen bolt I reckon it will be ok.
I am no expert mechanic and rely on help from forumns and according reckon this may help somebody else who has this problem,
I suspect alot of these blower motor problems relate to dirty contacts and cleaning is every bit as good as replacing. If I found the brushes heavily worn down I had planned to purchase brushes only and cut / solder the new wires to the old.l Thankfully this was not necessary.
The car, by the way is a 1994 model with 118k miles,

All

 

[Ardveen1]

W124 Heater Blower

Just noticed an error in last post, The aerial ( dont knoe how that crept in ) should read the 'wiper arm'.
Also I forgot to mention that having cleaned the brushes refix the springs on top of them and push back the retaining clasps to hold the springs in place before testing the repair.
Apologies for a few other typos, must re-read the posts before I submit them in future