Gutting that old microwave oven for a fan

microwaveLast year my expensive over the range microwave oven decided it didn’t like me too much and gave up.  After doing the basic troubleshooting, I decided to only verify fuses etc.  There is just a bit too much risk involved in self diagnosing a microwave that puts out over 2,000 Volts on the output of the transformer.


So what better way to say farewell to the scrap of metal then opening it up and salvaging some of the parts.  My primary focus was to recover the fan used for the range hood and anything that might be useful at some point would be a bonus!  This process actually started the day I replaced it with the new one last year and then the microwave was set in the corner.  I fifugred I’d find the time to go through it at some point.

Exhaust fan with capacitor

Well I found a use for that fan and when I started trying to figure out how to wire it up I realized I needed the starting capacitor to use it.  So, it was finally time to rip the cover off and find out what else I could salvage as I went hunting for the capacitor.


So what did I find inside?  Well I eventually found the capacitor tucked away to match up with the exhaust fan.


I also found 3 micro switches, a rotatory encoder, a small geared 120V motor, and two smaller fans with 120v motors attached.  Who knows when any of this might find a project to call home, but for now it will sit in my parts bin.


Back to that motor, this was the only label Fan LabelI found on it other than some quality control labels.  But what did it mean?  I could easily discern the A/C logo on the left and was pretty confident that the M was motor.  I also knew that TP wasn’t toilet paper but refered to the Thermal Protection and CAP wasn’t intended to be a hat you might place on your head but was the capacitor.  The specs printed on the label weren’t going to be much help and apparently Google didn’t help other than a lonely aftermarket replacement fan assembly.


My problem with the diagram was that I wasn’t sure if it was trying to indicate a single position switch between each of the leads (Black, White, Gray and Brown) or if I was going to add power to all four lead to get full speed.  Having decided that this fan was going to be used for exhausting the gasses from the new laser I just purchased, I went over to the “unofficial” Full Specturm Laser Forums and made this post.  After a bit of discussion, nobody had a definitive answer and the best advice I got was to yell “FIRE IN THE HOLE” before probing it with AC… 😉 LOL


Why not, I had nothing to lose and figured it was a switch so I setup a power strip with a breaker, twisted some wires together and attached my ammeter clamp.  After flipping on the power bar the motor sprang to life with a huge woosh, I had found high power!  After checking the remaining wires and documenting my results I had determined that it was indeed a 4 speed fan.


BLACK (B) = 2.07 A
WHITE (H) = 1.52 A
GREY (L) = 1.15 A
BROWN (S) = 1.07 A


Now I figure I will probably build a small Arduino based micro controller with some relays to control this beast along with design and laser cutting out an enclosure.  Stay tuned for updates!



    • The colour codes for the wires are listed above, infact one of the photos is actually off of the fan and show the wiring diagram which was really handy.

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