I’m starting on a few more minor projects now that the car is getting closer to being road worthy. One thing that really worries me about the car is the non-functioning heater blower motor. Exchanging this motor is a difficult and time consuming job and one that I’d like to avoid if possible.
Determining if the motor is bad is a pretty simple process. First, checking to make sure the filters at the air intake behind the chrome grill in front of the windshield is a good idea. If any debris makes it past these filters it can prevent the motor from turning. If this checks out, next step is to jumper the switch.
You can access the fan switch connections by removing the speaker in the center of the dashboard. The switch is part of the upper left (blue) heater lever. Remove the connector and check for 12V when the ignition is on. Once you’ve found it, jump the 12V to one of the other pins. Each of the three other pins are one of the fan speeds. If the fan runs, you’re in good shape! If not… check your wiring carefully, but you might be in for a fan replacement.
I’ve found several early W108 and W109 cars that had functioning heater blowers, but faulty switches. I’m not so sure this is as common on later cars with the redesigned heater levers.
So, since the switch was my problem, I decided to remove the lever assembly and rebuild it. Thanks to some mice who made a home in the dashboard, they were in pretty rough shape.
I have covered the first part of removal of the levers in this old article. Follow up to step 6 to gain access to the heater levers. In short, you must remove the radio, ashtray, and cigar lighter. At that point, you must disconnect all the cables from above and below. This is a bit difficult, but possible. Be patient and keep track of all the small clips!
Once the cables are off, you can remove the lever assembly by removing the two nuts that hold the chrome dashboard piece in place.
Below are a few pictures of the heater lever assembly removed from my 300SEL and the first steps of disassembly. Remove the black caps from each of the large plastic shafts to remove the levers.
Additional care must be taken for the blue lever since it is part of the switch assembly.
The three pictures above show some areas you should exercise caution. The blue lever must be removed together with the switch assembly. Two screws at the top of the switch assembly hold it in place. Also note the cable lug that sits in each of the top levers will fall out when the lever is removed. And finally, the last picture shows the spring loaded mechanism that produces the stops for each fan speed. Be careful not to loose these small pieces.
After inspecting the switch parts, it was pretty clear why it didn’t work. The photos above show the dirt and oxidation covering the contacts.
Removal of the lower levers is quite easy… they should just pull out with the shafts. They’re connected together via a linkage which I didn’t see a need to take apart.
Next step is to throughly clean all the parts. I used a mild soap and soft cloth to ensure I didn’t scratch the plastic pieces. I used some emory cloth to clean up the electrical contacts.
Reassembly is straight forward. I used a white lithium grease on all the moving parts.
I need to repair the wiring for the lighting before installing the levers back in the car. Don’t forget to check the bulbs and switch with a meter to ensure they’re working correctly. Also check the movement of all the cables in the car. Its likely these will need lubrication or replacement.
Do these levers look different from the ones in your car? In 1968, the interior of the W108 and W109 were changed somewhat for safety reasons. The later version of the levers were much more prone to breaking, but safer in the event of an accident. Its worth noting that I’ve never seen a set of early solid plastic levers broken unless severely abused.