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  •  » FYI Ford, Classic Mustang Tech Discussion
  •  » Heater speeds and residtor

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    6/08/2019 4:04 PM  #1

    rtmjr13@optonline.net
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    From: Long Island New York
    Registered: 3/12/2014
    Posts: 271

    Heater speeds and residtor

    Hello everyone, hope all is well. 67 mustang 390 gt fastback non a/c.
    My blower has no force behind   it, all 3 speeds are very week. What could cause this? Years ago it would blow paper away from the defroster vent. Is there a difference between the 67-68 resistor switches?
    I just put in a new radiator, shroud etc and decided to finally tackle this issue. Could it be the on off switch itself that needs checking? I do remember way back jiggling the switch and everything  speeding up but it has been changed since then. Where do i start?
    Thanx

     

    6/08/2019 4:25 PM  #2

    Ron68
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    From: Mukilteo, Washington
    Registered: 4/01/2013
    Posts: 1,589

    Re: Heater speeds and residtor

    rtmjr13@optonline.net wrote:

    Hello everyone, hope all is well. 67 mustang 390 gt fastback non a/c.
    My blower has no force behind it, all 3 speeds are very week. What could cause this? Years ago it would blow paper away from the defroster vent. Is there a difference between the 67-68 resistor switches?
    I just put in a new radiator, shroud etc and decided to finally tackle this issue. Could it be the on off switch itself that needs checking? I do remember way back jiggling the switch and everything speeding up but it has been changed since then. Where do i start?
    Thanx

     I ran into this a while back when I replaced my heater core. I had previously installed a new blower motor, and I was never happy with the results - low flow, hardly any heat or defrost. When I put the heater box back in after rebuild, I figured I would T/S the blower. My what a difference polarity makes........ I had the wires reversed so the blower was turning the wrong way. It blows gangbusters now. I would check that out for sure.

    68 coupe - 351W, 4R70W, 9" 3.25 -- 65 convertible - 289 4v, C4, 8" 3.00
     

    6/08/2019 4:41 PM  #3

    Glens 1965 50
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    From: Tomball,Tx
    Registered: 4/01/2013
    Posts: 278

    Re: Heater speeds and residtor

    Possibly motor getting weak....plugged up heater core on the fin side (Old foam beaks away and can land on it) or Micky mouse and family built a home in there.

     

    6/08/2019 4:47 PM  #4

    lowercasesteve
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    From: Auburn, Ca
    Registered: 4/01/2013
    Posts: 1,256

    Re: Heater speeds and residtor

    Another place to check is the blower motor ground.  I don't remember the details, and a bad ground could cause your problem because of too much resistance at the ground.

    Original owner - 351w,T-5, 4whl disks, power R&P
     

    6/08/2019 10:27 PM  #5

    wsinsle
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    From: Belle Vernon, PA
    Registered: 4/01/2013
    Posts: 1,704

    Re: Heater speeds and residtor

    All good suggestions, I would have never thought of Ron68 idea. If the motor is running but not blowing try reversing the leads at the motor and see if you start getting air flow. Now if the motor seems to be spinning fine and no air, then you may have blockage or the fan cage is slipping on the motor shaft. 

    If the motor just seems to be running slow then problem is probably a bad motor or ground or loose positive. Positive comes from the fuse. You could squeeze the terminals together on the fuse to make a tighter connection, this may help.

    At this point probably a bad ground or motor. To check bad ground you could unplug the yellow wire from the fan motor and jumper the motor to ground, The motor should run at full speed, You could also unplug the yellow wire from the fan switch and jumper it to ground, If  the motor runs good under either condition either the switch is bad or the switch ground is bad, Keep in mind the motor gets its ground from the switch.
     

    If this forum can't fix it, it isn't broke.
     

    6/09/2019 12:43 AM  #6

    rtmjr13@optonline.net
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    From: Long Island New York
    Registered: 3/12/2014
    Posts: 271

    Re: Heater speeds and residtor

    Ok, will check un the am-thanx for everything Still dont know what T/S means. Is it important? Would it help to maybe clean the 3 position heater switch itself? It la the original switch. If so, what to use to clean it? Trying to cover all bases.

    Last edited by rtmjr13@optonline.net (6/09/2019 12:55 AM)

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    6/09/2019 5:37 AM  #7

    josh-kebob
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    From: Madison, AL
    Registered: 4/06/2013
    Posts: 2,902

    Re: Heater speeds and residtor

    Trouble shoot

     

    6/09/2019 8:39 AM  #8

    red351
    I FYI 24-7

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    From: Carlisle, PA
    Registered: 5/31/2018
    Posts: 445

    Re: Heater speeds and residtor

    As what ron68 mentioned. After an hour squeezed  under the dash on the 72, I find that not everybody thinks the red wire should be the hot on a new blower motor.

     

    6/15/2019 6:57 PM  #9

    rtmjr13@optonline.net
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    From: Long Island New York
    Registered: 3/12/2014
    Posts: 271

    Re: Heater speeds and residtor

    Well-finally found the problem, after making sure everything is installed properly, found that the left heater hose was shot and barely attached to the blender. It had small  holes all through it that you couldn’t  see unless you put a light source behind it. Got a new hose set, should be fine will find out tomorrow. After checking out all of the suggestions, should  be tight!
    One more  thing, it seems that the 68 resistor is different from the 67, my 68 was built in late 67, so it has the same switch as 67. Does anybody know of the 68 switches being unavailable? And what they look like?

    Last edited by rtmjr13@optonline.net (6/15/2019 7:02 PM)

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