Some parts are easier to replace than others. No real mystery there, but it’s also true that some parts are easier to replace if you know what the heck you’re doing. In this case, the blower was failing in my ’97 M3. Hot and cold air wasn’t coming out with much force . With a driving tour and the promise of warm weather coming up in a couple weeks, I had to act quickly.

Diagnosing the problem was easy enough. Research online showed the blower resistor (also called the final stage unit) to be the likely culprit. It simply controls the fan speed. A call to Bavarian Autosport in Portsmouth, New Hampshire confirmed my suspicions. They had none in stock, but had a handful on the way to them in 2-3 weeks.  Not soon enough to help me. Luckily, they worked some kind of magic and arranged to have one sent to me in a couple days. My guess is that they got it from an alternative, less profitable source, just to satisfy me. Kudos to the crew at Bavauto.com.

While the part was en route, I checked out some DIY videos. A couple of them were kind of misleading, but I eventually found what I needed for my car. The part arrived without incident.  So far, everything was going fairly well.

Mysteries under the Dash

When I dig into unfamiliar territory I learn new stuff. Things might, however, get a little broken in the process.

From what I could see, two pieces under the dash needed to be removed to get access to the resistor. One is directly above the knees. I call it the driver’s side “knee panel.” Real OEM calls it “Trim panel, lower left.” Not very creative. The other is a vertical piece that covers the speaker, incorporating the foot rest. You’ll be equally impressed with its name; “Lateral trim panel, lower left.”  I just call it the “sidekick.”

The knee panel is easy enough to remove. It’s simply a matter of a few screws and disconnecting the underdash light and then releasing two connections to some kind of (diagnostic?) port. Even after a good bit of research, I have no idea what that port is. Just goes to show how little I really know about my car. With the panel removed, I could see that the fiberboard had been broken. Probably by a previous hack mechanic. Rather than replace the part, I simply used bits of duct tape. I’ll have to rethink that later.


Lacking the patience to consult more sources, (like the Bentley manual in my toolbox) I was flying blind when taking off the sidekick piece. This time it was my bad, as a couple bits got broken in the process. One of them is a little elbow shaped tab. It was easily re-attached with Super Glue. Still, feelings of frustration started to surface.


Resisting Removal

With the two panels removed I had “easy” access to the resistor… but only on my knees, at a very awkward angle. I now believe that I’m qualified to be a contortionist in a side show. As long as I keep a chiropractor close at hand.

Having gained access, I was silly enough to think that the rest of the process would be smooth sailing. Dead wrong. The war had only just begun. One saving grace was the very comfortable B-G Racing mechanic’s mat I recently bought from Mittler Brothers. It really helped my knees.

B-G Racing Mechanics Folding Mat

Disconnecting the plug from the resistor is the next step. It’s supposed to be simple, but it wouldn’t cooperate. I elected to first remove the part from its “cavity,” and take a shot at using both hands to unplug it. Stage 2 of frustration set in as I discovered that the screws holding in the resistor were “star” screws. Rats. Time to head to the hardware store for tools.

Armed with the proper tools, access was still awkward. It took several attempts to finally remove the screws. Grrr. Frustration mounted. I took a break.

Musical Interlude

Using a simple set of powered computer speakers in my garage, I typically play some kind of music from my phone. This time, I turned to a video I recently found on YouTube. It’s a recording of World Endurance Championship race cars testing at Monza. The sound is beautiful, soothing music to me, a race fan.

With the right music pumping into my garage, the work became more tolerable. There were times, however, when I felt like unleashing a string of expletives strong enough to burn a hole in the ozone layer. I refrained.

The Wrong Part?  

The part in question finally released its grip on its home of 20 years. Although joyful about my triumph, my happiness  was crushed. I found that the new part looked different from the old one.


Performing the work on Sunday meant that a call to Bavarian was out of the question.  Disappointed, I slotted the car back in its normal spot in the garage to finish another day.

Moday’s call to Bavarian yielded happy results. As it turns out, the new part was correct, the difference being attributed to an improvement in design. I happily replaced the part and started to button up the panels.

A Hard Fought Success

Patience pays off. Impatience, as I should know by now, creates problems. Like when I fail to make a note of the proper order in which panels should be reinstalled. After a couple attempts, I got things MOSTLY correct. Still, the kicker panel didn’t properly fit with a piece along the door sill. This started a whole new fight. To make the pieces fit well, I removed the sill piece.

If I’ve ever been a “black hole” of shade tree mechanics’ work, I found myself in one here.

There’s no way I can describe the battle I had getting the sill piece properly reinstalled. Nor do I wish to. I’ll simply tell you that the fight had to do with properly fitting the end toward the back seat in its carpeted cubby hole. What would have taken a trained professional about a minute, took this rocket scientist about an hour. At one point my hope of getting it right nearly dimmed to everlasting blackness.

I’m not sure how I eventually got it right, but I did. Probably by accident. But I’m happy to say that I did complete the job to my satisfaction. I get to put this one in the win column, but what a pain in the fan(ny) it was.

And if anyone can tell me what that mystery port is, I’d like to know.