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 27 2021, 12:37 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 |
@DRPHIL914
Great job gutting that beast! Especially so if you did it without breaking any of the clip plastic stanchions. We've got a mystery. Love it. So the good news is that youre saying the resistors roughtly make sense measued post to post. Low = 1.5 ohm initial to 2.1 ohm 2nd time. Perfect! Medium = 3.4 ohm initial to 4.0 ohm 2nd time Perfect! High = something is jacked up. I'm a little leary of your meter given that very 1st round of measurements measured 0.8 ohm on everything and now things are measuring much better for the medium and low resistors but way, way off for High. Something very odd going on here. We're going to stay here for a bit until we can 1) verify your meter is OK, or 2) Get repeatability to the readings, or 3) find some other root cause that explains all this weirdness. Ideas to move forward: 1) Are you abslolutely sure the meter leads aren't having connectivity issues of their own? I've had leads similar to yours, where you can unsrew the plastic lead housing from the metal tip, and the lead wire is soldered to the test tip. I've had bad solder joints on these type of leads before. Beware of these type test leads. a) I'm going to assume this isn't likely and that you performed the low and medium measurements after doing high and getting 121 ohm on high and by measuring 4 ohm type connections on M & L immediatly following the 121 ohm we can be partially convinced the problem isn't in the test lead. 2) When you did measure the high postion is there any chance the aligator clip wasn't making good connection on the high post? If you tried wiggling the aligatior clips to scratch the post and/or pressed the clip together while wiggling to get though any post corrostion and you measured 121 ohms multiple times, we'll assume it wasn't a fluke of the connection of the test lead. 3) If High is indeed repeatable at 121 ohms: a) let's look very closely at the copper trace connections on the resistor block for small crack, signs, of corrosion, or bad connectivity. b) Are the connector pin posts soldered? I think I recall they are. Could be a cold solder joint between the high post and the wire and/or copper trace. Sometimes you can see a cold solder joint with a 5-10x loupe. Other times I've just had to re-heat the solder and it improves. c) any chance the motor rotated ever so slightly between measuring L & M to when you measured High? I'm wondering if the motor brushes are worn and all of sudden had high resistance to the motor commutator when you happened to measure high? I'll tear my blower down tonight and to verify how the resistor pack is built and see if I can get some good photos to point you toward the motor brushes and the bearings to see if we can get your motor freed up in order to bench test it. |
DRPHIL914 |
Jan 27 2021, 01:17 PM
Post
#56
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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 |
@DRPHIL914 Great job gutting that beast! Especially so if you did it without breaking any of the clip plastic stanchions. We've got a mystery. Love it. So the good news is that youre saying the resistors roughtly make sense measued post to post. Low = 1.5 ohm initial to 2.1 ohm 2nd time. Perfect! Medium = 3.4 ohm initial to 4.0 ohm 2nd time Perfect! High = something is jacked up. I'm a little leary of your meter given that very 1st round of measurements measured 0.8 ohm on everything and now things are measuring much better for the medium and low resistors but way, way off for High. Something very odd going on here. We're going to stay here for a bit until we can 1) verify your meter is OK, or 2) Get repeatability to the readings, or 3) find some other root cause that explains all this weirdness. Ideas to move forward: 1) Are you abslolutely sure the meter leads aren't having connectivity issues of their own? I've had leads similar to yours, where you can unsrew the plastic lead housing from the metal tip, and the lead wire is soldered to the test tip. I've had bad solder joints on these type of leads before. Beware of these type test leads. a) I'm going to assume this isn't likely and that you performed the low and medium measurements after doing high and getting 121 ohm on high and by measuring 4 ohm type connections on M & L immediatly following the 121 ohm we can be partially convinced the problem isn't in the test lead. 2) When you did measure the high postion is there any chance the aligator clip wasn't making good connection on the high post? If you tried wiggling the aligatior clips to scratch the post and/or pressed the clip together while wiggling to get though any post corrostion and you measured 121 ohms multiple times, we'll assume it wasn't a fluke of the connection of the test lead. 3) If High is indeed repeatable at 121 ohms: a) let's look very closely at the copper trace connections on the resistor block for small crack, signs, of corrosion, or bad connectivity. b) Are the connector pin posts soldered? I think I recall they are. Could be a cold solder joint between the high post and the wire and/or copper trace. Sometimes you can see a cold solder joint with a 5-10x loupe. Other times I've just had to re-heat the solder and it improves. c) any chance the motor rotated ever so slightly between measuring L & M to when you measured High? I'm wondering if the motor brushes are worn and all of sudden had high resistance to the commutator when you happened to measure high? I'll tear my blower down tonight and to verify how the resistor pack is built and see if I can get some good photos to point you toward the motor brushes and the bearings to see if we can get your motor freed up in order to bench test it. i did rotate the motor while hooked up and on the low and medium they change of course during turning it and return to the static number, the high same way, it returns to the 120 reading like 3x , on off back, test side and end of then. yes they are soldered , will try and clean contacts a bit and recheck the positive/high lead, have to find my solder gun, but they look and feel solid. |
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