There is a ‘known fault’ with the air conditioning that affects the Mercedes-Benz SLK 170, and more frequently as it gets older. The fan switches itself on and off as it pleases.


The source is frequently the regulator, seen above on the lower left. It gives rise to other problems as well so if your air con is messing with your comfort it is time to do something about it.

Replacing the regulator is an easy task, in fact perfect as a first time d.i.y job.

Tools required:

Illustration of toolsEssential: Cross head screwdriver and Torx (star) head screwdriver. I use an electric screwdriver not only because I am lazy but not having to turn the screwdriver makes it much easier to feed screws into their slot when  they are going in upwards.

Handy tools: 

Small mirror. You will be looking upwards under the passenger side dashboard so unless you are fit and lithe, a mirror makes it easier to see what you are doing. 

Brush. To remove the debris you will find has been sucked in. I use a make-up – blush adder – brush.

Small light. It is dark under there. An alternative is to work on the car in daylight and place white paper in the footwell.

Circuit tester. It is possible, although unlikely I’ve been told, that there is another cause of the problem. It can be useful to test that current is going to the fan.

Where it is:

The fan is behind the passenger glove locker. To get to it the cover has to be removed.

001   002

It can be seen as the black bit in the image. It is held in place by two cross head screws at the front of the panel on either side, one being shown in the second image.

Remove the screws. I find it best to place them in a box that is out of the way of elbows.

The panel must be pushed back half an inch until the front drops out of its retaining lip. Pull it forward to release the two hidden clips that hold it up. The rear end is lipped over the floor carpet and has to be lifted up to allow the panel to be removed.

You will be presented with another panel, shown in the picture below.

You can see the power connector to the right. This needs to be pulled off gently taking care not to break the clip holding the wires.

If you do not know if the regulator is faulty, you can test the three outputs. Switch on the ignition, switch the fan to zero and see if there is any current. Then try with position 1 through to 5. The current should gradually increase. If you replace the connector and the fan does not come on then try the regulator.

You should now remove the cover. The two light coloured clips, seen in this image, should be pushed together as far as they will go.


Don’t press too hard. The cover might need a gentle tap to release. It is hinged at the rear. It will pull clear forwards. The regulator and fan will be exposed as well as debris, such as leaves and dead insects. Brush around everywhere you can.


The regulator is the silver item with the connectors to the right in the image. It is held by two torx screws. Remove these and it will drop away but remain held by the wires. I removed the fan as well, held by four torx screws (there’s one hidden at the back – hence the mirror I suggested) in order to get all the debris out. I’m told that the rear screw can be accessed with the regulator in place. I didn’t bother to try.

007  011

The final screw is by the bend in the red wire in the picture.

The regulator has just two connectors and they are of unequal size, so the wires will only go in their rightful places. Whilst remembering what goes where is not that difficult, it is nice to know that you can’t mess up. I’ve got stories.


Once back in place, test whether the fan works. If it doesn’t, it is either not the regulator at fault or you’ve put the same one back.

Don’t use an electric screwdriver to tighten the screws holding the cover in place. It is all too easy to over-tighten.

When replacing the final panel, it is easy enough to press the little internal clips slightly from outside.