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Super Moderator UK 2002 SLK320 Blue
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2,939 Posts
Discussion Starter #1 (Edited)
Arrived home after a quick trip round last week to find that the blower fan wasn't working. Mildly annoying, but now, with time on my hands, I thought I'd take a look and see what it is. The blower fan is located behind the glove box on the passenger side of the car. To get at it, undo the two screws at the front of the panel under the glove compartment, slide the panel to the back, drop down and gently pull forward to release it.

573855


Next pull the three pin plug out of the base of the blower fan.
573856


Then slide the two clips towards each other to release the cover
573857


After removing the cover from the blower, THIS greeted me. Leaves and bracken. Bah. Checked the fuse in the fuse box under the bonnet - blown. (30A fuse (green) in position 36 - be aware, this circuit is permanently live) Don't replace it yet - do the due dilligence and check things through first.

573554


Now this situation can go one of three ways:
  1. It's just dirt - clean it up and we're good to go
  2. The blower has burnt out
  3. The resistor (or hedgehog) has burnt out
So let's dismantle it, clean it up and see where we go:

First, disconnect and remove the resistor as this makes access to the four T20 Torx screws that hold the blower in place

573557


It looks clean, luckily, but carry on and undo the four T20 bolts and take it out.

573558


The resistor, however, looks a bit gummed up. You can remove the debris with a stiff paint brush and a wooden coffee stirrer.

573559


The blower looks clean - but do check inside the motor (spot the leaf behind the copper wire there...) The blower was also stiff to turn, so a little lubricant on the bottom bearing would help prolong the life of the blower. Make sure the blower is free to turn and get rid of any debris within the fan blades and anything that is in the housing. (none in this case) Squirt some contact cleaner on the blower commutator to help clean the contacts and the brushes.

573560


And re-assemble. We now need to test that everything works. Connect up the blower motor to the resistor but leave the 3-pin plug disconnected.
573566


Set the fan controller to zero (off). Now connect the fuse (a new one if you have to...)

573567


Now, back with the blower, we can complete the diagnostics. Connect the three pin plug. We'd expect the fan not to run at all (no key in the ignition / heater control turned off)
  1. If we're lucky and it's just debris, then nothing should happen until you turn the ignition on and turn the fan control up. Result
  2. If the fan turns at full speed as soon as you plug the 3-pin plug back in, then the resistor has blown. (this is what happened to me!)
  3. If the fan doesn't turn, even when you turn the ignition on, then it's likely the blower has gone - or both the blower and the resistor. This can be expensive.
I now need to order a new resistor and replace it, so I'll leave the re-assembly till later.
 

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Super Moderator UK 2002 SLK320 Blue
Joined
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2,939 Posts
Discussion Starter #2 (Edited)
So the resistor arrived (I didn't buy the cheapest - but I did get one with a warranty)

These resistors fit a number of Mercedes vehicles of this age, so it was no surprise to find that the new resistor came with different wiring to the old one so I had to swap the wires from the old to the new resistor. The connectors are different sizes, so it's easy to switch them.

It's easier to re-connect the resistor to the blower before you try to assemble the whole lot:
573860


But it ain't so easy to balance the blower in position and get the first of the T20 screws back in place.... I had to do this one-handed
573861


Get the screws in place - but don't do them up tight till the blower is properly seated in the housing. Then screw in the resistor.
573862


(and a prize to the person who can spot the slight change in the fixings...)

Once it's all in place, repeat the testing described above.
  • three pin plug disconnected
  • insert fuse 36
  • connect the three pin plug - the fan motor should not move
  • switch on the ignition and adjust the control knob
  • check air blows freely
All good? Then disconnect the three pin plug and line up the cover with the slots in the back of the housing
573863


gently close the cover and slide the two locks outwards (they're shown unlocked here) Be gentle and don't force them. Remember the plastic is 20 years old.
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Then reconnect the three pin plug
573865


You can test again if you want - I just assembled every thing after that.

My SLK has footwell lighting fitted - so I had to reconnect the cabling for that. (I'd disconnected this when I took the panel out):
573866


Now offer the panel up to the two slot towards the front of the car in the depths of the footwell:
573867


Then bring the panel up, align it and slide the panel towards the rear of the car. Then put the two screws back in.

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Job done.

There is only one thing left to do: Tidy up and go for a drive to test that the blower works. (y) ?
 

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Premium Member 2005 SLK200K 'Little Growler'
Joined
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674 Posts
Arrived home after a quick trip round last week to find that the blower fan wasn't working. Mildly annoying, but now, with time on my hands, I thought I'd take a look and see what it is.

View attachment 573554

After removing the panel under the glove box and then the cover from the blower, THIS greeted me. Leaves and bracken. Bah. Checked the fuse in the fuse box under the bonnet - blown. (30A fuse (green) in position 36 - be aware, this circuit is permanently live) Don't replace it yet - do the due dilligence and check things through first.

Now this situation can go one of three ways:
  1. It's just dirt - clean it up and we're good to go
  2. The blower has burnt out
  3. The resistor (or hedgehog) has burnt out
So let's dismantle it, clean it up and see where we go:

First, disconnect and remove the resistor as this makes access to the four T20 Torx screws that hold the blower in place

View attachment 573557

It looks clean, luckily, but carry on and undo the four T20 bolts and take it out.

View attachment 573558

The resistor, however, looks a bit gummed up. You can remove the debris with a stiff paint brush and a wooden coffee stirrer.

View attachment 573559

The blower looks clean - but do check inside the motor (spot the leaf behind the copper wire there...) The blower was also stiff to turn, so a little lubricant on the bottom bearing would help prolong the life of the blower. Make sure the blower is free to turn and get rid of any debris within the fan blades and anything that is in the housing. (none in this case) Squirt some contact cleaner on the blower commutator to help clean the contacts and the brushes.

View attachment 573560

And re-assemble. We now need to test that everything works. Connect up the blower motor to the resistor but leave the 3-pin plug disconnected.
View attachment 573566

Set the fan controller to zero (off). Now connect the fuse (a new one if you have to...)

View attachment 573567

Now, back with the blower, we can complete the diagnostics. Connect the three pin plug. We'd expect the fan not to run at all (no key in the ignition / heater control turned off)
  1. If we're lucky and it's just debris, then nothing should happen until you turn the ignition on and turn the fan control up. Result
  2. If the fan turns at full speed as soon as you plug the 3-pin plug back in, then the resistor has blown. (this is what happened to me!)
  3. If the fan doesn't turn, even when you turn the ignition on, then it's likely the blower has gone - or both the blower and the resistor. This can be expensive.
I now need to order a new resistor and replace it, so I'll leave the re-assembly till later.
Very usefully described and photographed.
 

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Super Moderator UK 2002 SLK320 Blue
Joined
·
2,939 Posts
Discussion Starter #4 (Edited)
Very usefully described and photographed.
Thanks for that.

The thread started off as a discussion, so I didn't detail the approach to the blower originally. I've remedied that now the job's done.

Hedgehog (blower resistor) on order. Due Friday (tomorrow).
 

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Super Moderator UK 2002 SLK320 Blue
Joined
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2,939 Posts
Discussion Starter #5
I've updated the first post and edited the second to show the assembly process end-to-end.
 
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