Aux Fan Bearing Lube

[528i-1981]

Guys - I've been thinking about how to lube the bearings on my aux fan, which is drawing too much current and roasting my 25A fuse. The plastic around the terminals in the fuse box is shiny, showing that it's been way too hot.

The problem I'm trying to solve is how to clean and lubricate the bearing without removing the fan, which will require removing the condenser and and the radiator. Evacuating the AC system to pull the condenser from the hard lines is something I'd rather avoid. And even with my recent spin-on fan upgrade, pulling the rad is a PITA.

I believe this video shows the construction of the fan, or at least a very similar one on the E30.



While there is insufficient clearance to pull off the fan blade, and the hub of the blade is deep, I can remove the nut holding it to the motor shaft. That will allow the fan blade hub to pull slightly back from the bearing. I think that I should be able to drill one or more small (7/64") holes spaced from the fan hub mounting hole, angled toward the center, which will permit the straw of a can of WD40 Specialist Degrease in there, followed by some white lithium. I found Flexstraw FS250 50" flexible spray straws on Amazon, which are 0.095" in diameter.

If the video is correct, there is only a bushing on the side of the motor shaft closest to the condenser, which should be easy enough to flush out and regrease.

Has anybody tried this? Any thoughts?

[528i-1981]

The approach worked. The fan turns much easier, but my fuse is still heating to around 140 degrees, which is way too hot. I'm going to have to replace the aux fan.

Can anyone suggest a good replacement fan and source? Siegal used zip ties and a lightweight aux fan in his AC book, but if there's a retrofit that anyone else has tried, I'd like to know about it. Also if you have a known-good spare you'd like to sell, PM me, although I'm inclined to use a new fan to upgrade the performance over stock. Motors have come a long way in 40 years.

Thanks, gents.
Eric

[Mike W.]

I'd amp out the fan and find the draw before I replaced it. That fuse/fuseholder is marginal at best and really just isn't up to the current draw thru it. Is it under good tension? I've had to bend things around to get more pressure as a loose connection will generate additional heat. Guys on the E28 board have even gotten creative and installed a blade fuseholder and fuse.

If the fan spins freely I'd guess the fuse area itself before the fan.

[528i-1981]

That's a good idea, Mike. I assumed that if the fuse wasn't popping the draw was under the fuse rating. I'm thinking I'll measure at the connector, but I'll need an ammeter with a higher rating than 10A. I have made sure the prong has plenty of tension. I have not taken the fuse box apart to peer inside, and that has to be less work and hassle than replacing the fan.

PS. Glad to hear you're holding out OK out there.

[528i-1981]

All of the external wiring of the aux fan checked out okay. Fan was drawing under 22 amps. But removing the wire from the underside of the number 17 fuse showed how toasty things got below deck:



I was surprised that both of the red/green wires heading to the Stage I and Stage II relays were ganged onto a single connector. And that connector got hot along with the prong and the fuse. In hindsight not surprising given the whole conduction thing.

I ended up wiring an automatic thermo-resetting 30A breaker directly to the battery with 8 AWG wire and then solid-core 12 AWG wire from the breaker to the relays. I think I could run an oven with this wiring. Number 17 fuse has been retired, perhaps to rise again like a Phoenix from the melted plastic. But any future use will be in the 10A range.