Defrost fan rehab and rebuild thread (fresh air fan), or How the heck do if fix this thing? |
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Defrost fan rehab and rebuild thread (fresh air fan), or How the heck do if fix this thing? |
DRPHIL914 |
Jan 21 2021, 08:55 AM
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#54
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Dr. Phil Group: Members Posts: 5,808 Joined: 9-December 09 From: Bluffton, SC Member No.: 11,106 Region Association: South East States |
I have been dealing with this for 12 years, a non-running defrost fan. i even pulled this out 2 years ago and rebuilt it with new flapper seals and main body seal then made sure fan turned but didnt bench test the motor or resisitors, so as a result it still does not work properly. i will be documenting this because 914rubber and Mark will soon be putting together a kit for this that includes all the hardware seals and even a motor i believe, BUT i still have problems and questions!!! so i am starting this thread to get information on diagnosing the common causes of it not working and how to fix it, and then document the rebuild and replacement of the motor, fan, resistor and maybe the control unit in dash. Others have documented the reinstallation of the fan and the cables so i will not duplicate that. and we may want to link other threads hear that have done that as well.
Mark is sending me a kit soon, so while i wait for it, i will have to get some more information about the wiring and resistors function and how to test them . I had this out last week and tested 3 different control units due to thinking that my issue was a control issue, because it runs on one speed, #2, and anything else does not work and it will then throw the fuse. most assume this would be caused by bad slider unit but i tested 3 of them and 2 are like new with no wear on the sliders , still same result. so i am suspecting the resistors /plug aparatus . If anyone has done this and cares to share how to examine and test that for proper function, lets start there. Resistor function, which lead is which and examination of the control units I will take pictures of mine tonight and post those soon. once this figured out and fixed i will do a full step bystep on reassembly too. Looking for lots of help and input on this, thanks!!! Dr. Phil |
Superhawk996 |
Jan 28 2021, 07:11 PM
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#55
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914 Guru Group: Members Posts: 6,469 Joined: 25-August 18 From: Woods of N. Idaho Member No.: 22,428 Region Association: Galt's Gulch |
Note: Really need to remove resistor pack to do this properly.
When I removed mine, I found the low speed resistor bi-metallic switch was deformed closed. However, due to corrosion on the switch it was actually reading as if the switch were open. (IMG:style_emoticons/default/lol-2.gif) Can't assume anything. So reminder on the contact positions and keyway positions. Let's roll though the verification of the resistor Here is the low speed after I filed the bi-metallic switch contact lightly with an ignition file. Because the bi-metallic switch is closed and now making contact it's measuring as a 1.1 ohm short across the resistor - bascially acting like a high speed bypass. Note: from here on out I have the resistor bank leads that would normally go to the motor shorted together in same manner as @DRPHIL914 was doing previously Now low speed again with the bi-metallic switch bent back to open position with a pair of pliers to put it where it should be. Medium speed with bi-metallic switch open High speed (no resitor, and no bi-metallic switch for this one basically a direct short). Finally here is a picture of the orientation of the resistor bank connector and keyway as I photographed it in the photos above. I also did measure the armature of my now defunct motor -- the armature of the motor measured in the range of 0.8 ohms to 1.2 ohms depending on where it was rotated to. So if you're measuring the resistor bank in the as installed postion, you would expect all values above to have 0.8 - 1.2 ohm added to them. This correlates pretty well to what I measured initially on my blower motor + resistor as an assembly. |
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