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Rob Peters

AC/Heater Blower Issues

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I am ready to get my Air Conditioning system recharged and have noticed when I select either Heat, Air, Def the only speed I can get is HI.  The Low, Medium 1 and Medium 2 speeds are not working.  From what I am reading and from looking at the wiring diagrams, from what I can gather it seems that my issue would be with my blower resister assembly.  

From what I can gather, this resister is mounted in the evaporator plenum.  When I was up at the garage this evening to do the wiring for the new POA Valve pressure switch I noticed it appears this resister is not screwed to this plenum but it looks like it is riveted to the plenum.  Has anyone ever replaced this blower resister?  If so, how did you reinstall the assembly?

Is there a good way to test this resister?  From what I can see it does not look like this would be an issue with any fuses.  Any thoughts or suggestions would be greatly appreciated.

rob

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I’ve had mine out to check when I redid my AC and my son in-law Jamie checked it out with an multimeter and the resistance check OK to what he a found online

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What you describe definetly sounds like a blower resistor. they can be checked for proper resistance. I dont remember cutting rivets but it's possible. 

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Larry, did you just use some self taping screws to reinstall it?  When I was researching it on line I did not find any values for the resister so I will keep looking.  In reality if I can determine the pin-out numbers I can check the resistance on the resisters. 

rob

  

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I just spent the past 45 minutes trying to figure out resistances and for which pins on the resistor assembly but could not find anything on line.  I will need to keep looking.  Most of the blower resistor's I see on line only have 4 pin/blades coming out but looking at the wiring diagrams for the 70 it looks like it should be 6 pin/blades.  

rob

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I think it's rare for all speeds to be out, if one resistor section was burned or it's wire broke, only that speed would be dead.

Have you checked the switch on the dash? Don't forget, the switch gets it's power from the heater fuse in the fuse panel in the car. The firewall in-line fuse only feeds the high speed relay.

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Paul,

I  think you misread my original post up above.  The only speed that works on the blower is the High speed.  The ones that do not work are the Low, Medium 1 and Medium 2 speeds.  

If I am reading the wiring diagram correctly, the power comes in on the blower speed selector switch with the High speed being pretty much the full 12VDC and the Medium 2, Medium 1 and Low speeds running through the blower resistor to reduce the Voltage, thus reducing the speed of the blower.

Being that the High speed works, the main thing common in the other speeds is the blower resistor.

rob

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Mine had screws in it when I bought the 72 and they are just some metal screws with a hex head. I was really careful when I reinstalled t make sure I did not strip them out. Some times I think I am super man or the terminator which we all know is a false narrative. 

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Mine has hex head screws holding it in, I did change it once with one from parts car, it didn seem to help I never really went any farther  with it because I rarely use the heat/ac

20190520_094843.jpg

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While in Carlisle I picked up a new blower switch from Lutty's Chevy Parts.  I installed it after I got home today and I now have my blower working on all speeds.  Life Is Good!!!

rob

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Yay!!! Congratulations! Nice to have a/c on all speeds I bet. 

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