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Blower motor

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Old 09-16-18, 11:51 AM
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Blower motor

I've been having intermittent problems with the blower motor on my S5 that started sometime last winter. I'd start out driving to work without heat because the blower motor was not working, and then half way into work the blower would startup. This wouldn't happen all the time, but only recently started becoming more frequent. More recently, I'd be driving to work on a rainy morning and the windows would start to fog up due to a non-working blower motor. With all the rainy we've been having, I had do something about it and fast.

The blower motor circuitry on the FC is a bit complex. I've reviewed the related wiring diagrams and searched the many treads on this subject. After reviewing clokker's and calpatriot's suggestions (which go back to about 2009), I decided that I'd start out by replacing the blower motor since the relays appeared to be working as I could hear/feel them clicking. Blower motor was listed the first suggested item to check. Also, my logic was that the blower motor on my car had been running almost continuously since I bought the car new in April 1990. That's over 28 years of continuous operation on the blower motor. I had a suspicion that the brushes were almost worn down to nothing after 28+ years of operation.

Depending on the source, Mazda wanted $250-350 for replacement blower motor (UB94-61-B10). As usual, ridiculous Mazda prices! I then searched the Rockauto website and found three different replacement motors ranging in price from $23 to $38. I bought the Four Seasons motor p/n 35493 (https://www.rockauto.com/en/moreinfo...192395&jsn=359). Turns out that the only differences between this motor and the original were the placement of the electrical connector and length of the shaft. The original motor had the connector mounted directly to the motor rather than on the short lead. The new motor had a slightly longer shaft, but in the end everything mounted the same as the original motor.

The blower motor is located under dash next to right hand side kick panel. The motor is mounted vertically with three screws holding the motor and plastic cover to the blower assembly. All screws are pretty accessible using a 1/4" drive ratchet set. There's also a small (i.e., 2-3" long) rubber hose that runs from the motor enclosure to the blower assembly. The replacement motor didn't come with the blower wheel. So, you had to remove the nut and pry-off the wheel and remount on the replacement motor. I put the old motor in a vise and used a pry bar to remove the plastic blower wheel. It took some effort to pry off as it was a tight fit onto the shaft. I plugged in the connector and tested the new motor before remounting and everything worked fine. I was regretting doing this job, but it turned out to be extremely easy. If anybody is having similar problems, than first thing I'd suggest is checking the blower motor.

Attached is a photo of my original blower motor with end cover removed. The brushes had only 1/16" or so length remaining. Looked like they were actually scraping the commutator as there were a lot of fine copper dust in that area. The motor was loaded with leaf debris and dirt, which might have been causing my problem. A lot of this debris had fallen out when I removed the cover. So, you're only seeing a portion of the debris in this photo.


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Old 09-17-18, 06:42 AM
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Very nice!! Thank you for sharing the correct solution. Here's hoping the problem stays resolved. I have seen bad solder joints in the logicon cause intermittent blower issues but nothing too extreme or common. Usually the blower just won't work at all if that's the case. Won't stop mid drive.
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Old 09-17-18, 04:12 PM
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Logicon was the next item on my list.
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Old 09-19-18, 10:53 PM
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Rebuilding the logicon is a piece of cake. Any electrolytic capacitor is worth replacing, and you should at least check with a multimeter and see if your diodes are still good and if you have a fried transistor or two.
I went through and replaced all the electrolytic capacitors in my car. Made a huge difference.
Have you had problems with the variable speed of the blower (other than it being full of crud)?
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Old 09-20-18, 10:39 AM
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Originally Posted by professionalpyroman View Post
Rebuilding the logicon is a piece of cake. Any electrolytic capacitor is worth replacing, and you should at least check with a multimeter and see if your diodes are still good and if you have a fried transistor or two.
I went through and replaced all the electrolytic capacitors in my car. Made a huge difference.
Have you had problems with the variable speed of the blower (other than it being full of crud)?
No problems that I recall. The blower is usually set to one speed and I don't change it too often. The only problem that I'm having with the variable speed control is that it doesn't slide smoothly anymore.

I did buy a used logicon with the intention of eventually swapping mine out. I might rebuild it before swapping it out. Would you have a list of the capacitors in the logicon?

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Old 09-20-18, 07:58 PM
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https://www.rx7club.com/2nd-generati...en2n3-1120533/
Here is the thread link for the logicon components. He has a pretty good layout for what to do on those. You are mostly just wanting to replace the electrolytic caps, as those tend to rot over 30 years.

If your blower still seems weak, or doesn't work below full throttle, you'll definitely want to check/replace the blower transistor (in the blower box with an aluminum heatsink), as well as check all the components in the amp section of the logicon. I kept burning through blower transistors (the big round metal ones) about every 6 months, until I took apart the amp and checked it. Had 2 blown diodes that were allowing current to go where it shouldn't. Let us know how it goes, can send some pics if you need.

When ordering components, digikey is probably easiest. If items are listed as unavailable, check Ebay for the cheapo importer people. They have the rest of the stuff.
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