This is an easy repair that I did as part of my over-the-winter maintenance work while I'm driveway camping in Florida. I had ordered the motor last July so it was sitting here waiting for me when I arrived. I had been having problems with the original fan motor since shortly after I got my van – it failed to come on and I had to open the hood, remove the cabin air filter, and give it a push to get it going. My chassis was the first of the extended body Sprinters Roadtrek built on, and had been sitting for over a year when we began work on it, so it must have developed a flat spot on the motor armature or a bearing problem during this lengthy waiting period. Last summer,
I was blasting the heater on high as I climbed a 10% grade to help shed excess engine heat, and started smelling something hot. I worried that my engine was overheating, but the temperature gauge said it was still OK, and I finally figured out that it was the fan motor, not the engine, that was getting hot enough to smell when running on high. I avoided running it that fast for the rest of the season, and ordered the replacement motor.
Now, Mercedes doesn't make these motors, they buy them from a supplier, and rather than assist in putting the dealership owner's kids through college by ordering one from my local Sprinter facility, I started looking around online. There were a bunch of no-name replacement motors for $60ish of dubious quality (one company was actually named “Replacement Motors”) but Rockauto had one manufactured by VDO (the company that makes many quality German car products, including Porsche gauges) for $35 or so – “wholesaler closeout, one left”. I bought it. Opening the box, I see that it was a return – one of the tabs where the motor attaches to the air duct is broken, but that's no big deal, there are four other tabs to hold it.
Installation is a snap – you empty out your glove box, gently bent the two tabs at the top to open it fully, and undo the three screws at the bottom. these are Torx fasteners so you'll need a special screwdriver. With the glove box off, you remove the glove box liner by undoing the three screws across the top and the hidden one on the right under the panel to the right of the glovebox. To get to this, you undo the screw at the bottom and pop this panel loose. Pop the glove box light out of the rectangular hole it sits in (or undo the plug) and the glove box liner will come right out. Everything is modular in these Sprinters, making for easy assembly and disassembly. Right in front of you is the motor. Undo the screw holding the right end of the support directly across the bottom of the fan motor to give yourself a little more room, loosen the two-wire plug which powers the fan, and you can grasp the fan and turn it slightly counterclockwise to release and remove it. It's held in by the tabs, one of which was missing on my new fan.
Once I have the two fans to compare, I notice that the spinning resistance is much higher in my old fan than the new one, confirming my decision to replace it. These are just like any electric motor – they get old and tired. Your vehicle is full of these motors – wipers, seats if you have electric seats, windows, fuel pump, washer motor etc. If you're going to keep your vehicle for decades you'll probably end up visiting a few of these motors along the way in your journey. In maintaining the family fleet over this winter I have already replaced two of them in other vehicles – a fuel pump and a window motor. They just wear out over the years.
I put the new fan in and turn the ignition on to test it, and discover another problem – the person who tried to install this motor previously, in addition to breaking one of the tabs, had also broken the retaining clip which holds the two-wire plug into the fan motor assembly, so when you try to push the connector onto it the whole thing goes into the assembly, eventually contacting the fan blades and making a racket. Now I know why I got such a good deal on this fan – it was previously installed by a gorilla. I end up making a plastic dowel pin to secure the plug in the assembly, and everything worked according to plan.
Just to the left of the fan motor is the resister that makes the different fan speeds. How you get four different fan speeds out of one voltage is run the current through increasingly larger resister circuits until you slow the fan down to the speed you want. In normal cars these resisters are just loops of Ni-chrome wire hanging out in the air stream inside the heater duct – but Mercedes engineers, who obviously have a lot of time on their hands, made a fancy heat sink of circular rods that is quite impressive, if you happen to like poking around under your dash looking for interesting things. This resister also has the tabs-and-rotate setup like the fan. If you lose some of your fan speeds, this is likely the culprit.
So now I have a fancy new competition racing VDO fan motor in my Sprinter, and no longer have to endure worrying smells while i do hill climbs out west in my 11,000 pound vehicle. I'm ready for Pike's Peak – Sharon was expressing some interest in going there just yesterday, and now I'm prepared.