Mercedes heater fan bearings

Don't know, but (as I am sure you know) such things are usually oilite bushes. As long as you can see one of the end-plates, it should be obvious because a ball bearing is likely to have a larger diameter and greater thickness.

I haven't done this job on a merc, but I have on many other cars, always they are a brass type bearing, cleaning and lubing always get them going again. You can always run it up off the car and keep pouring oil through till it comes out clean.

I lubed the heater fan on a Vectra because it made annoying dry squeaky noises. The bottom bearing is in a sort of cup, so I left it swimming in a mL or so of light oil, rather than the water that collects there naturally. It ran beautifully.

It was a serioulsy tedious job to get the fan out, entailing hanging upside-down over the passenger seat with my head under the dash!

But one very hot day some of the oil vapourised while the car was parked. I then ran the fan and the oil vapour caught fire - stopping the fan killed the flames, but the commutator was then contaminated with soot so the fan would not start reliably.

So make sure you drain any spare oil away. It would be better to have had a PTFE or nylon bearing that would have been lubricated by rainwater!

In message , MrCheerful writes

Thanks. That's reassuring that I'm on the right track. I'll soak it for a few days, then try running it up.

Interestingly (to me anyway), I've just looked up the oil I'm using, which is left over from when I used to service bearings in audio devices like tape machines and record players. The two types of oil, Shell Clavus and Tellus, used to be referred to as steam turbine oil, but now seem to be listed as refrigerator compressor oil and hydraulic fluid respectively.

Thanks also to Newshound for his reply.

In message , Graham J writes

I'll now make sure I drain any loose oil away!

What a stupid design these things are. The corrosion on the heater resistor block's heatsink mounted in the same area is terrible. I assume the heatsink and motor are not designed to be water cooled!

Tellus was always a hydraulic oil, turbine oils were Turbo followed by various letters.

In truth it wouldn't normally make much difference what type of oil you use. Turbine oils have anti rust additives which might help in this wet location, but 3 in 1 might be even better. In theory, avoid EP gear oils because some of the organic sulphur additives corrode some types of bronze.

As you say, tape recorders and record players often use oilite bushes too, so their lubricants should be fine. Sewing machine oil is another good bet, nice and thin so easy to get to the bearing, and will tend to soak in. Readily available in small containers, expensive per litre but then you don't need to buy a litre.

Could the thermal fuse for the lower speed settings have (also) blown? Often the speed is controlled by 3 resistors mounted in the airflow to keep them cool. If the fan has stalled then the protective one time thermal fuse may have blow.