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Windshield Wiper Relay Replacement
 
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Pelican Technical Article:

Windshield Wiper Relay Replacement

Steve Vernon

Time:

1 hour1 hr

Tab:

$10 to $50

Talent:

**

Tools:

Philips head screwdriver driver, Mercedes tool 140598023300,

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Relay

Hot Tip:

Do not pull hard on the cluster

Performance Gain:

Working wipers

Complementary Modification:

Check all your gauge bulbs

If your windshield wipers have stopped working because of a failed relay you are probably thinking, "Great, it's only a relay." While relays themselves are simple to replace, the location of the windshield wiper relay is interesting to say the least. If you work on cars long enough, from time to time you will find things that make you scratch your head and wonder just what were the engineers thinking. The wiper relay on the W123 is one of those occasions. For some reason the relay is located behind the instrument cluster and to replace it you will first need to remove the cluster. There are a couple of things you need to be aware of; it is a tight fit behind the cluster so do not try and yank the cluster forward when removing it, you will need to reach your hand behind to release a few things to get some working room. Also if your cluster is old and you are using the cluster removal tool, make sure it is seated on the cluster and not the front plastic shield as you can pull this straight off the cluster if you do.

Make sure that you disconnect the battery ground cable before you begin as you are going to be with the cars electronics.

Over the years your car may have been serviced by multiple people including previous owners and this can lead to parts replaced with different size fasteners and hardware. The sizes of the nuts and bolts we give may be different from what you have so be prepared with different size sockets and wrenches. If something is different on your vehicle please let us know and share your info to help other users. If you have any questions or comments or even a different procedure you would like to share please leave it below and please leave your vehicle information.

NOTE: We have removed the steering wheel so we could get pictures of the wiring but you do not need to remove your wheel to remove the cluster and change the relay.

Disconnect the negative battery cable (red arrow).
Figure 1

Disconnect the negative battery cable (red arrow). Make sure it cannot make accidental contact with the battery while working.

Remove the five screws holding the under dash panel and remove the panel, please see our article on under dash panel removal for additional information if you need it.
Figure 2

Remove the five screws holding the under dash panel and remove the panel, please see our article on under dash panel removal for additional information if you need it.

With the lower under panel removed you can reach up underneath and push the cluster forward and out from the dash.
Figure 3

With the lower under panel removed you can reach up underneath and push the cluster forward and out from the dash. I prefer to use the cluster pulling tool that Mercedes sells or you can make your won by bending a couple of long pieces of sturdy metal 90 degrees at the end.

Insert the instrument cluster removal tools between the dash and the cluster and turn them 45 degrees so they engage the rear of the housing taking care that they do not damage the material on the dash.
Figure 4

Insert the instrument cluster removal tools between the dash and the cluster and turn them 45 degrees so they engage the rear of the housing taking care that they do not damage the material on the dash. Make sure that the tools are hooking on the side of the housing and not the front glass as this gets brittle over the years with age and if you are not careful you can pull the front shield away from the housing rather than the cluster out from the dash.

Gently pull the cluster forward until you can separate the electrical connections on the left side (red arrow).
Figure 5

Gently pull the cluster forward until you can separate the electrical connections on the left side (red arrow).

Reach your hand in behind the cluster and unscrew the speedometer cable from the rear of the housing.
Figure 6

Reach your hand in behind the cluster and unscrew the speedometer cable from the rear of the housing.

You can now tilt the housing forward and use a 10mm wrench to remove the tach cable (yellow arrow) if your vehicle is equipped with one.
Figure 7

You can now tilt the housing forward and use a 10mm wrench to remove the tach cable (yellow arrow) if your vehicle is equipped with one. In this picture you can also see where the speedometer cable has been separated (red arrow).

Remove all of the other electrical connections and bulb holders and remove the cluster form the dash.
Figure 8

Remove all of the other electrical connections and bulb holders and remove the cluster form the dash.

With the cluster out you still cannot get to the relay, it is located behind the insulation (red arrow).
Figure 9

With the cluster out you still cannot get to the relay, it is located behind the insulation (red arrow).

Pull the insulation out of the way and voila, the simple windshield wiper relay reveals itself to you (red arrow).
Figure 10

Pull the insulation out of the way and voila, the simple windshield wiper relay reveals itself to you (red arrow). At this point you may want to take a minute and write Mercedes a letter asking them just what were they thinking?

After all of this, replacing the relay is the same as all the others; simply pull it out and push a new one in.
Figure 11

After all of this, replacing the relay is the same as all the others; simply pull it out and push a new one in. (red arrow). Installation of all of the other components is the reverse of removal.

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Page last updated: Mon 12/5/2016 03:02:41 AM