Well, after months of putting up with an A/C blower fan that kept chirping, mainly at the motor speed that's used the most (in Auto setting) I finally solved it!
Using the Bentley manual, I removed the blower motor from the engine compartment and with a little bit of advise from the Brit who designed the siemens version of this motor (mine is Bosch) I stopped it from chirping!!
I re-oiled the bearings with 3-1 lube oil and cleaned the commutator carefully. The whole process took a couple of hours. Thanks to those who answered some of my questions. The Bentley manual is a must and I'm sorry I didn’t buy it years ago.
A replacement blower assembly varies in price between $350 and $500 depending where you look online. Obvioulsy installing a new blower motor would be the best solution but so far I've only spend $85 for the Bently Manual.
Check out http://www.hodson.eclipse.co.uk/Smiths.htm
and his response below.
Sometime the www blows me away with what you can find.
That seems a lifetime ago to me now. The E46 Siemens design motor that I
worked on was for the South African and SA export market only (Australia,
Africa). Unless Smiths have done some brilliant deal, it's more likely that
you have a Bosch motor in the US (I'm pretty sure Bosch had the rest of the
worldwide E46 market). However, there are really only 2 areas of contact
likely to cause a squeaking noise (especially during cold weather). The
bearings and the commutator / brushes.
We used sintered metal bearings, and they went out with 4 small dabs of
grease sitting on the outer surface, which would be absorbed into the
bearing during the motor's life. I couldn't tell you now exactly what type
of grease it was, but be careful not to over do it. If oil or grease gets on
the commutator, it turns the brushes to paste, and you wouldn't believe how
quickly your commutator will break down! There is usually a fling off ring
that separates the bearings from the commutator.
The other not so obvious thing, it that if the commutator is too smooth, it
can be noisier, when we machine the com, it has a MINIMUM groove depth spec.
(we're talking 30 microns or something, if memory serves). If too smooth you
get a burnishing effect, and it's actually noisier. You want I nice healthy
goove in the direction of rotation to maintain a good electrical contact and
strangely enough reduce noise.
I'd look at the bearings first. See if an enginnering supplier can recommend
grease for sintered bearings, and apply it with a syringe.
The motor is a double blower, with plastic spoked blower wheels,
press-fitted. Almost impossible to get off without breaking them without a
proper jig / puller.
The motor at full speed in the housing draws around 21 amps at full speed.
Outside of the housing it would draw more than that. You need a pretty meaty
benchtop supply, but it wouldn't hurt to try for low speeds. Our lab
supplies could put out 50 amps, but they weighed 50kg! You could just run
some meaty cable from under the bonnet, then you'll have speed control too.
Just one final comment. The motors are not really made to be disassembled.
The end caps are riveted (crimped) in place, the bearings are held in by
press fitted spring clips, the rotors I already mentioned. Hopefully you can
do what you need to without taking it apart though.
Good luck, thanks for the trip down memory lane. I'm a programmer now, and
to tell the truth, I really miss the engineering days! Hence the long