Ventilation fan carbon brush and repair

[Chai]

My ventilation fan started playing up during operation: it occasionally squealed (high-pitched metal rubbing on metal sound) and the speed was not constant.
It eventually turned out that only the fan shaft bearing was dry and a lube resolved these issues. However, this article also provides the dimensions of the carbon brush required for the early 107 SL and SLC fan if you need to replace them.
Interestingly, the fan rotor in these early SL/SLC cars are metal and held by a grub screw, unlike the plastic and friction fit used in the 1980s that I read about (where insertion of the plastic fan in boiling water is suggested to remove it from the shaft).

FAN REMOVAL
Use a Phillips screwdriver to remove the cover over the fan assembly on the firewall. Take care with this plastic as they’re no longer available.
There are two tiny screws holding the flap down and another two screws to remove the fan speed resistor from the firewall.

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Four 10mm bolts hold down the fan and these are located on each corner of the unit. The entire fan unit can be removed from the car after that.

FAN DISASSEMBLY
Circlip/snap ring pliers must be used to remove the clips holding the upper and lower plastic halves of the fan. Don’t force them using a screwdriver or similar as the plastic tangs on the cover can snap.

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My fan had been previously removed and shows damage along with the inappropriate use of mastic-type sealant on the rubber gasket, which caused the fan to stick to the gasket. You’ll see sticky tape used to hold the two halves of the fan cover together where some previous repairer had snapped the plastic tangs on the cover in one of the later photos.

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[Chai]

FAN VANE REMOVAL
I didn’t remove the vanes as I didn’t have the correct size Allen key. The 2.5mm hex key did not fit and the 3mm was too large. (Maybe it’s an imperial 7/64-inch size grub screw.)
The vanes are balanced so, if you remove them, please mark the left and right hand sides, also how deep they’re installed into the shaft.

FAN SHAFT LUBE
The lubrication of the rotor bearings was difficult as the fan vanes were not removed.
Apply heat to the spray tube with a fine wire inside it and create a 90 degree bend. It is then (just) possible to spray in the direction of the bearing with this setup.

[Chai]

CARBON BRUSH DIMENSIONS
The fan carbon brushes for this motor are 6mm x 8mm and around 15mm in length.
I had pre-purchased a set from the US and these were too large – 8mm x 10mm and 20mm long. However, it’s only graphite (pencil lead material) and very easy to sand to a suitable size.

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The picture shows the re-sized ‘new’ brush above the old/existing. The 17mm ‘new’ is too long and still needs to be shortened another 2 mm in order to allow the spring to be installed.

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[Chai]

CARBON BRUSH REPLACEMENT
Pry open the tab covering the spring over the carbon brush using a small screwdriver.
You’ll need a high-Wattage soldering iron to remove the electric lead to the carbon brush. Mine were still serviceable so I re-installed them.

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[Chai]

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CLEAN BEFORE REASSEMBLY
Clean the air-conditioner evaporator fins and vacuum out the base where there’ll be a collection of small leaf bits that have been sucked in through the mesh covering the air intake vents.
Also check the water drain holes on both sides (one is under the hot water hose) are not clogged with leaf bits. Pour a little water down these drains and you should hear the splash as it exits from the firewall onto the floor.

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[TheMadRacoon]

Thanks for Posting, Chai. Great for future reference.

[CraigB]

Great info Chai - thankyou

[AMG]

I recently performed a similar operation on my 201, but wrote it up on 190rev.

the brushes are replaceable on 201 / 124 blowers, but the bearings are a pillow ball bearing and are not user serviceable.

on a 201 the brushes are type M41.

The units benefit from removal and thorough cleaning in degreasing solvent (prepsol) before blowing clean with compressed air and relubricating the bearings. Unfortunately the 201 axial motor is far less robust and the bearings require a more frequent service interval than once every 25 years. :dance:

Thanks for the 107 specific write-up!

[TheMadRacoon]

Chai,

Does it matter if one of the dimensions is 1-2mm leds than specified? Eg 5x8x15mm or 8x6x13mm? There are some listed for power tools, eg for de Walt etc. Some come with a spring already attached, would these be ok? I'd have to solder an extension as the spring takes up the length of the supplied lead.

CARBON BRUSH DIMENSIONS
The fan carbon brushes for this motor are 6mm x 8mm and around 15mm in length.
I had pre-purchased a set from the US and these were too large – 8mm x 10mm and 20mm long. However, it’s only graphite (pencil lead material) and very easy to sand to a suitable size.
20160207-143801 450SLC ventilation fan.JPG
20160207-143842 450SLC ventilation fan.JPG

The picture shows the re-sized ‘new’ brush above the old/existing. The 17mm ‘new’ is too long and still needs to be shortened another 2 mm in order to allow the spring to be installed.20160207-152302 450SLC ventilation fan.JPG
20160207-154547 450SLC ventilation fan.JPG

[AMG]

You should be able to order the brushes from Ashdown Ingram near to you, or go see them. just give them the dimensions and ask them to look it up on quantum.

[TheMadRacoon]

Thank you Joe :)

[CraigB]

Thanks Chai

You can file them to fit if a little bigger. Non-locals may need to google the locations but I drove my 1924 Amilcar from Adelaide to Ceduna - Pt. Lincoln - Whyalla and back to Adelaide. I only got to Pt. Augusta when the starter stopped working, and it is a pig to crank start. I pulled the starter and went to the local auto sparky who was busy and he handed me a box of brushes and a file - said find the closest and file to fit. Must be over 10 years ago and haven't touched the starter again.

[TheMadRacoon]

Finally got some time, energy and motivation to make a start on this. I'm a naturally cautious person, more so with things I haven't tried before and where the risk of damage to a 43 year old car is not to be neglected.

So a query Chai and others.....

After removing the two screws holding the resistor box, the next step would be separating the plug from the resistor box socket. How is this done? By simply holdong the resistor box and plug in each hand, gripping and pulling apart? Or by inserting a small flatblade screwdriver (!) and gently prying the black plug from the brown socket base (moulded plastic)? Or is there a clip that has to be released first (how?).

Or something else completely?

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BTW discovered one possible source for a longstanding rattle: a bolt on the driver's side engine mount shock absorber can be spun freely and lifted up/down a few millimeters. There's a nut on top that's tight, so perhaps a bush has fallen out or maybe that's the piston rod and the rest of the damper is long gone. Will have to have a good look and compare to engine mount diagrams.....but first, the blower.

[Chai]

Pull the plug away, use a flat screwdriver for leverage if needed. Do not recall any clips holding it down.
It's the same type as the other plugs that look similar in the engine compartment.

[TheMadRacoon]

Thanks Chai, I'll give it a go!

[AMG]

I would avoid putting a screwdriver near anything electrical -

2 reasons:

1. Have you disconnected the battery first?
2. The connector plastic gets brittle after 40 years of thermal cycling in an engine bay.

If you think it's a little siezed, first use contact cleaner and switchlube on the plug, at the join. Let it work a little-
Use your fingers to pull the plug - it should not require any great effort. If it is stuck, then you will need to use a penetrating lubricant - inox / wd40 etc.
If you find yourself having to use that, make sure you absolutely clean the connector afterwards. WD40 is a kerosene/parafin base and will wick up the wire under the insulation.

Try to avoid using brake cleaner - but if the plugs are covered in oily soot and muck, then by all means, clean as appropriate. Just ensure that the connector is cleaned afterwards with some CO cleaner and switchlube - then you'll not have to worry about corrosion or siezing connector pins again. :occasion5:

[TheMadRacoon]

Thank you Joe. Timely and good advice.

I tried contact cleaner. Let it soak. I thought I was making a little progress until the resistor box cage / guard came off.... and with it the corner of the flange of resistor setup's base, the corner with the threaded insert for mounting it on the firewall :(

Ah these things are meant to try us, and to remind me how much I respect those with an aptitude for such things.

Down the track I could consider a 3D printed replacement for that base. But let me cross the bridge I'm at first. Used WD40 and after 10mins (impatient?) not even the tiniest movement. Hmmm. Guess it's not good with it just sitting there, wicking up the electrical wires while that plug is on there like a leach on your calf.

I shall persevere. Wait until I see the whites of their eyes and all that.

Hmmm. Not even the tiniest movement....bummer.

[Chai]

Here's another option. I recall the top of the connector can slide off sideways, exposing the internals of the plug. It's been a while now and I can't recall the specifics of this action.

Hope this photo helps.

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This allows each wire connector to be pulled individually off the prong.
However, this means the wires can become mixed up so TAKE A PHOTO of the wires before you pull any off - or use this if the colour coding is the same.

Regarding the screwdriver - use the small electrical type, with the 4mm wide tip.

[TheMadRacoon]

Thanks Chai!

It did look as if the black (on mine) cover slid off. Looking at some ebay photos it seems the resistor box has the male prongs (plug) and on the engine side of the firewall is in fact the socket.

Removing the cover can help me test resistances but I'll eventually have to separate plug and socket so I can remove fan motor assembly.

Will try again. In hindsight I should have left the resistor nox mointing screws on so it is attached to the firewall, and just tried to pull the socket off.

[TheMadRacoon]

So I got the plug off. Really annoyed I broke the corner of the resistor block flange off, though. No use dwelling on that. All the pins were very clean on the resistor box side so it definitely was a snug fit.

I removed the fan and it appears original - nothing broken around the clips, original sticker still on. And joy of joys the metalwork around the fan and heater core is not perferrated. Was dry in there despite the gasket on the fan box pkastic cover being dry and disintegrated in parts. There is surface rust which needs to be treated to give it another 40 years.

But it got me thinking: beside the broken mounting glange noted above I snapped off the two lower studs that the fan locates onto. They weren't corroded thtough, though the tops of them were and I used plenty of WD40, though obviously didn't allow enough time to penetrate. The studs aren't large in diameter and they sheared off drom the torque applied.

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The point is I wonder if I should be doing anything myself on this car. It's not perfect, but original and the bad bits I've discovered aren't bad or as bad as I feared.

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So, reality check: am I making things worse by attempting repairs myself? After all, I leave all the mechanical work to specialiats and don't skimp (it's my work car: drive 200km one way, park it, a few days later I drive back) as I need it to be reliable. And my intention when I bought it was not to do the work myself.

Perhaps I'm heading towards the question: who should I take it to? If only Mercmad lived in beautiful Victoria :think:

[Chai]

My ventilation fan started becoming noisy when driving on undulating roads - the bump when car comes down on its suspension was when a grinding sound can be heard coming from the fan.
The lubrication of the bearings using a spray nozzle equipped can of lithium grease was performed. A piece of wire is needed to nudge the nozzle a little sideways in order for the tip to line up where the shaft of the motor enters the bearing. Some tissue stuffed inside the fan helps capture the grease over-spray.

20231219-172618 450SLC ventilation fan - spray grease on motor bearing.JPG

The question I have is, how can I remove the rotary fan to better access to the fan motor bearing?
I found a 3mm allen key was able to loosen the bolt that appears to hold the fan onto the motor shaft (making me doubt whether I actually have a 3mm in my kit as I had previously reported the 3mm wouldn't fit). However, the rotary fan would not budge - there was no slack after the bolt was loosened.
I'm guessing a small gear puller is needed but I don't have this tool.

20231219-165250 450SLC ventilation fan - spray grease on motor bearing.JPG

This tool will be something to have in hand the next time I have to grease these fan bearings again.