Mercedes Turn Signal and Hazard Lights

There seems to be mass confusion on how to solve malfunctioning turn signal and hazard lights
on the early 70’s and 80’s Mercedes-Benz models. Hopefully this article will put to rest any
further frustration.

A number of us who own or will own one of these cars, will experience the turn signal and
hazard lights flashing erratically or extremely fast. At first glance, it could easily appear to be a
burned out bulb or a connection at a bulb that is perhaps dirty and not functioning.

As with many cars, the turn signal and hazard lights are designed to flash at a faster than
normal rate to indicate a problem, primarily a burned out bulb. The idea of this fast flash is to
annoy the driver enough to force them out of the car to check for a burned out turn signal bulb
and replace it. When you do finally decide to take a look and notice that all bulbs are indeed
working, but the flash rate is still out of control, is where the confusion begins.

If all bulbs are working perfectly normal, not flickering or dim, the next step is the turn signal
and/or hazard switch relay. There are two different early variants on the hazard lights and relay
set up as the following photos show. The fist is a combo unit, while the second is a split system.
Check your particular chassis number for the proper relay and/or switch.

In the case of the early R107 or W107 (450SL or 450SLC) our focus for this project, the relay for
the turn signal and hazard are separate. The relay for the turn signal and hazard lights is behind
the instrument cluster and the hazard switch serves as just that, an on/off switch. While various
units appear similar in style, they do vary in function and number of pin connectors.

So let’s jump in and assume no turn signal bulbs are burned out and you are headed for the
relay.

Remove steering wheel by removing emblem with plastic trim removal tool.

Use a breaker bar fitted with a 4 inch extension and 22mm socket. DO NOT use the steering
wheel lock mechanism for the resistance you will need to loosen the steering wheel retaining
nut. To avoid the steering wheel engaging with the lock, insert key into ignition switch and turn to
position “1”. In addition, it may require an assistant to hold the steering wheel in order to loosen,
the nut. NOTE: You can remove the horn pad to make the removal a bit easier, but I would
prefer to leave as much as possible undisturbed in an older car.

Once the retaining nut is free, mark the steering wheel and steering shaft with appropriate
“marker”. This will allow you to return the steering wheel to it’s correct orientation.

With the steering wheel removed it is now time to remove the instrument cluster. If your
cluster is original, it will more than likely slip out quite easily as it is only pressure fit in the
opening and held by a rubber gasket with “fins”. Special tools are made to extract the cluster
and are quite easy to use. You can also extract it by pushing from behind.

With the cluster loose, gently pull forward far enough to remove all necessary connections.
WARNING: DO NOT attempt to start the car with the instrument cluster removed, unless you
have made advanced preparations to capture the oil that will spray out from the oil pressure
gauge line.

Now that the cluster has been removed, you will see the relay to the left. Gently wiggle loose
as to not crack the plug base and remove. Repeat the revers for installation of the new relay.

Repeat previous steps in revers order for the installation of the instrument cluster. When all
the connections have been fitted, test the turn signals and hazard lights by activating the hazard
lights. When all checks out, finish the reinstallation of steering wheel.

CAUTION: Be sure to properly torque the steering wheel retaining nut to avoid it coming loose
in time.

If by chance the relay does not correct your problem, you will want to check the hazard switch in
the center console for possible replacement. If all else fails, you should consult the original
wiring diagram and/or an automotive electrician.

HELPFUL PARTS:

Early R107 Flasher Relay - Bosch 0335200007

Early R107 Hazard Warning Switch-Genuine Mercedes 0018218851 

The early W123 Switch/Relay combination unit is very hard to source at this time. According to
Mercedes-Benz, the unites are not available and have not been in production for some time
now. They are however available on Ebay on rare occasion but upwards of $150-$200 for NOS.

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Written by :

West Kenyon

West Kenyon is a Multi-Media Design Consultant and automotive enthusiast. Cars in his collection include a 1956 Austin FX3-D, better known as a London Taxi, a 1965 Rolls-Royce Phantom V, and a 1975 450SL and 1981 240D by none other than Mercedes-Benz. West said, “owning one or a number of vintage cars is often an expensive proposition", which is why he does the majority of mechanical and interior work/restoration himself. West added, “not only does it save a significant amount of money to do the work yourself, it also provides full opportunity to know the job is being done with excellence and allows for an unprecedented appreciation and knowledge of the car.” For FCPEuro, West will focus on providing in-depth information on both the Mercedes-Benz R107, 450SL, D-Jetronic version and the W123, 240D. Glücklich Autofahren! (Happy Motoring)