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Heater Blower Motor

By Jerry Cole, Technical Advisor

You can spend huge amounts of money repairing a Mercedes if you want, but you don’t have to. There are so many ways to get the same top quality repair without sacrificing quality or originality. Here is a good example.

If you own an R107 SL with a chassis number below 042309, the heater blower motor is sold as an assembly and retails for $1220. For chassis 042310 and above, you get a break and it is only $680. What a deal, right? Do you suppose it is going to be in stock? Of course not. You’re going to be waiting for it one way or another, so why not save most of that money and end up with the same result? Keep in mind that this doesn’t just apply to R107s. Mercedes doesn’t make electric fan motors. You’ll usually find that they say something like Bosch on the actual motor. In most cases, it is the motor bearings that fail. Once in a while, the brushes fail first. What is important is that it’s the electric motor that has failed and everything else is still perfectly good, so why buy anything more than the actual failed component? A few minutes of research revealed that the Bosch electric motor for the R107 with chassis number below 042309 was Bosch part #0130063013. This may also be true for chassis numbers above 042310. A quick check of your particular application will tell. In order to see that the part was available, I had to enter the Bosch part number in the auto parts vendor’s search box. It appeared and was available for $62. If I just searched using the typical make, year and model drill down, the part would not appear.

In a few days, a shiny new example of my defunct blower motor arrived. Replacement of the blower motor on a R107 is actually quite simple. The blower motor is located underneath an access cover below the windshield in the engine compartment. With the access cover removed, you will be looking down at the top of the blower assembly. Unplug the electrical plug that feeds the blower. On chassis 042309 and below, the assembly is held in place at the four corners with 10mm nuts. Remove the four 10mm nuts and associated flat washers. Another difference on chassis 042309 and below is that the regulator is part of the wiring harness. The regulator is attached to the firewall with screws. With the screws removed, the complete blower assembly with wiring harness and regulator can be lifted out.

The plastic housing is held together with a series of metal clips. These clips can be easily removed with a flat blade screwdriver. With all of the clips removed, separate the two halves of the housing. Now is a very good time to break out a digital camera and start taking reference pictures. Take note of the following things: How the wiring harness feeds out of the case. The position of each squirrel cage on the shaft and which side of the motor each squirrel cage came from. They are directional. Note how the motor sits in the plastic housing. If there are any metal clips on the squirrel cages for balance, mark their locations in case they get bumped out of position. Once you are confident that you have enough information to reassemble it properly, lift the motor and squirrel cages out of the housing. I rinsed the plastic housing halves then put them in the top rack of the dishwasher. Yes, Tracey knows.

Now it’s time to transfer the squirrel cages from the old motor to the new one. If there is any rust on the protruding tip of the motor shaft, sand the rust off. That will make it much easier to slide the squirrel cage off of the shaft. With the aid of a pot of hot water to soften the plastic just enough, carefully slide the squirrel cage off of the shaft. Twisting motion helps. Reheat if the squirrel cage cools too much. When heating, don’t allow the squirrel cage to rest on the pan bottom or sides and be careful not to apply too much force. A broken squirrel cage is a very bad thing.

Slide the squirrel cages onto the new motor shaft, paying attention to direction and position on the shaft. Set the motor assembly in the bottom half of the housing and adjust the position of the cages until everything is well centered and nothing hits when the motor spins. Reassembly is simply the reverse of disassembly. I set my blower assembly in place and plugged it in for testing before complete installation. Success!

I know this all sounds complex, but it’s really quite simple and everything will make sense when you see it. You could actually say R107 blower repair is a breeze.

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