DIY Fix harman distribution blower without replacing!

Ryhder

New Member
Mar 18, 2018
1
Northwest Connecticut
Hello , after having a distribution blower failure on my Harman XXV I decided to tear it down and attempt to repair whatever may broken inside, I searched for any info on repair / rebuilding the electric motor but found only suggestions to replace it. In the spirit of saving $200 and possibly saving someone else $200, I decided to share my experience after I repaired the problem. Ok let's begin:

Problem : distribution fan not running, stove surface temps higher than normal

Status: all setting on highest levels, all lights in side panel illuminated (except igniter) no trouble codes indicated , 1 full day of no distribution blower.

Issues found : blower fan difficult to turn by hand , fails to turn on when switched to "test " mode

OK so out comes the fan.

At this point I should have began photographing, I did not. I may create a drawing to better help explain , or perhaps disassemble my stove for the purpose of teaching.

I digress,
Once the fan assembly is on the bench remove the fans from the centrally located motor. The fan housings must have a locking tab bent out of the way, and then they can be turned with a small amount of force to line up the 3 notches and tabs and then pulled straight off.

You will now have the motor with the square plastic " male" pieces pressed on to each end of the central spinning shaft. Don't worry they pull off easily with a little pressure from a flathead screwdriver.

Remove the 2 torx headed long screws that hold the motor together. The aluminum side plates can be removed now and the internal " drum" can be removed. Keep track of any spacers and their order as things come apart .

At this point you have the 1/4 inch thick shiny spinning shaft with its electromagnetic drum or metal drum in the center . (There is also a brass bushing on each side of the drum) Don't get caught up in the terminology, we're going to call these two the "rod" and the "drum".

This is where my fan had the issue. The drum had been bonded or glued to the shaft at the factory and now the bond had failed. The shaft could be nocked out of the drum and the shaft was blue and discolored.

So what is happening here? My guess was that once powered up , the drum would spin on the shaft and the fans would not spin, only friction would be created on the inside of the drum. Bad . Like a bicycle with no teeth on the sprockets.

So my simple solution to this was a series of dimples / dents on the shaft to give it something to hold on to . Take care not to bend the shaft obviously. But I used a hardened pin and a hammer to dent it in many places ( maybe 10 ). You only want to hit the area that will be inside the drum so be aware. Once the shaft is nice and ugly it can be pressed back into the drum . This should be a much tighter fit now . Mine was able to push in by hand with decent force and it seems to have been enough to bite in. The brass bushings also can be bonded to the shaft but once you are finished, the whole shaft and drum assembly should be one piece. At this point I decided to put the whole thing in the chuck of a drill and polish the outside of the drum. I do not have a great knowledge of brushless electric motors so this polishing may not have been nessicary or helpful , but that's what I did.

Now you can put your spacers and aluminum side plates back on and you have a motor. From this point on you should be able to spin the motor easily with your fingers and it should feel like a fan should.

Reassemble!

Note : if your fan suffered some type of electrical failure like burned wires or you can see something else has gone wrong while taking things apart then this may not be your only fix . My fan felt like it had a bad bearing but upon inspection I was surprised to find no bearings but this to be the problem instead. Give it a try before you spend 200 on a new one , this may be your problem , for about 1.5 hours of tinkering and use of baisic caveman hand tools this repair was all I needed.

Hope this helps keep you and your family warm in a pinch! Post any questions and if some has a junk fan to disassemble , the pictures would be worth 1000 words
 

jackman

Minister of Fire
Jan 15, 2013
532
Oregon