Bench test for 1973 rear defroster motor

Electrical & Ignition

  1. Branded

    Branded Member

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    Can anyone tell me how to test the rear defroster motor for my 73 Charger?
     
  2. PurpleBeeper

    PurpleBeeper FBBO Gold Member FBBO Gold Member

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    I don't expect there's anything "special" about it. Double check your wiring harness, but I'm pretty sure it would take 12 volts, so ground the body & put a 12V jumper wire to the motor's electrical connection. It should spin.

    If the motor is working fine, check continuity of the wires between the switch & the motor.

    If those are OK, check power going into & out of the switch

    And....grounds....grounds....grounds.....check all the grounds & clean metal contact points for all of them.
     
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    • Sahara

      Sahara FBBO Gold Member FBBO Gold Member

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      I did a bunch for my ‘70 Coronet, should be similar.
      I recommend that you make sure that there’s no mouse nest or debris inside, then just put 12 volts to it.
      If yours is pooched I have three good extras.
       
    • toolmanmike

      toolmanmike Moderator Staff Member FBBO Gold Member

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      • toolmanmike

        toolmanmike Moderator Staff Member FBBO Gold Member

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        Sorry for the poor video @multimopes . Hard to hold the phone and do the testing at the same time. LOL Hope it helps.
         
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        • multimopes

          multimopes FBBO Gold Member FBBO Gold Member

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          Thanks for your concern, I thought the video was just fine! I happen to have a 73 car myself and although it was stripped of all creature comforts for racing, I have the original fan motor and duct work in a box. I don't recall seeing the 2 electrical terminals like you show; are they mounted on the side of the fan?? Also, where is the factory switch located on the dash and what does it look like?; as my dash was also cannibalized during the gutting process. A picture is worth a thousand words! It's not really important but I feel while it's on my mind I'd ask before CRS creeps back in. I also don't like to hijack someone else's thread, but to save time, what the hey??? Sorry there Branded, I'm "the one who's scorned and ran!" (Thanks Chuck Connors!) I guess I'm also showing my age, LOL! :D
           
        • Nacho-RT74

          Nacho-RT74 Well-Known Member

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          motor gets two prongs because both speeds. The baquelite gets resistors inside.

          and this is the switch down the dash

          rr defog switch.jpg 000255d.jpg 000437b.jpg 000436b.jpg
           
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          • multimopes

            multimopes FBBO Gold Member FBBO Gold Member

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            Thank you Nacho, that is what I needed to see and do not have, LOL. I hope that all is well with you and yours down there!
             
          • Nacho-RT74

            Nacho-RT74 Well-Known Member

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            rr defog harness1.JPG


            The swith selects the wire to feed the correctly the resistor on the propper speed you select. ( plug to switch is not exactly like that on our 71/74 B bodies but still 3 ways one )

            and... well, we are here surviving. Right now another protest on the way
             
            Last edited: Feb 12, 2019 at 11:20 AM
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            • multimopes

              multimopes FBBO Gold Member FBBO Gold Member

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            • QuickBpBp

              QuickBpBp FBBO Gold Member FBBO Gold Member

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              I have a complete defogger switch assembly with intermediate harness (small dash harness) if needed...
               
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              • Nacho-RT74

                Nacho-RT74 Well-Known Member

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                yeap, actually switch pigtail reaches the kick panel... right ? then get the harness to reach the trunk. I made my own one between kick panel up to deffoger, parallel to the rear lighting harness
                 
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                • multimopes

                  multimopes FBBO Gold Member FBBO Gold Member

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                  Thanks Quick,
                  I am not sure of what was ripped out of mine, harness wise. A lot of stuff was just left disconnected behind the dash. The sad part is that I mounted a combination of electric cooling fan run lights and override switches very close and just barely above the actual switch locations. Shoot me a PM with a pic or two of what you have and how much you want. If I ever get the time to work on my car like I want to, I'll probably die from shock! LOL The weather sucked so bad last year I barely got time to drive it. You aren't that far from me so shipping should be cheap. Also. thanks again Nacho for your always appreciated help. My heater box was ripped out long ago so I can't even defrost the front windshield in the rain, let alone the rear. I have a replacement box but it would entail completely taking out the dash which with the roll bar coming down next to the doors and my old body not as flexible as it once was. If I actually had a heated garage I could do things like this much easier.
                   
                  Last edited: Feb 13, 2019 at 9:03 AM
                • QuickBpBp

                  QuickBpBp FBBO Gold Member FBBO Gold Member

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                  Yes it is short and goes over to connect the main harness. I have the entire set-up if needed. I have boxes full of this stuff Used and NOS, switches, wiring, motors etc...

                  IMG_7658.JPG
                   
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                  • QuickBpBp

                    QuickBpBp FBBO Gold Member FBBO Gold Member

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                    Sure just let me know what is needed easier to get it all at once...
                     
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                    • Nacho-RT74

                      Nacho-RT74 Well-Known Member

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                      actually you don't need to remove the dash. Glove box liner should be enough
                       
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                      • Nacho-RT74

                        Nacho-RT74 Well-Known Member

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                        I have an extra switch I grabbed from somewhere, but without the bezel. I think will use that to feed a underhood light and road lights thinking to add! Since it will never be used at the same time I can set one switch position for each one. Just have to fabricate the bezel

                        ( althought can't recall if this switch feeds both leads when using High speed, like AC blower switch does. If so, is just about add a relay to help on the switch )
                         
                        Last edited: Feb 13, 2019 at 9:21 AM
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                        • multimopes

                          multimopes FBBO Gold Member FBBO Gold Member

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                          Believe me Nacho, the mess behind my dash and the boogering up everything to save weight for racing left a real mess back there. I very carefully dropped the column late last year just to install the heat control switch piece, without cables,(just to fill the hole), and when I bolted it back up, the right rear brake light and signal stopped working. On top of that most of my dash gauges don't work and a custom panel with aftermarket gauges is installed below the center of the dash to the trans hump. There are 7 grounds connected under the column bolt. It's a nightmare!
                           
                        • Nacho-RT74

                          Nacho-RT74 Well-Known Member

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                          Get me an air bill and I'll fix that LOL. I never have being in NJ... closer was Pensilvania when I went to Carlisle Chrysler All Nationals in 2008 LOL
                           
                          Last edited: Feb 13, 2019 at 9:23 AM
                        • multimopes

                          multimopes FBBO Gold Member FBBO Gold Member

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                          Thanks for the offer nacho, LOL, if I had money, I would do just that. Do not regret never being to NJ, you ain't missin nuthin! I've been trying to sell my house and get out of here for over 10 years; am working rotating shifts and have to fly to Florida just to see my wife, and can't afford to leave without selling. Add to that, with the corruption in this state, if your septic system is over 15 years old, (mine is 32 years) they require you install a new system for over $30,000.00! Then there is the 2 percent exit tax to ice the cake! All in all, one might wonder why I am a tad disenchanted. I forgot also that there is a custom aftermarket radio in the home made center console thing as well in my car. The factory location is an empty hole. Check my photo garage to see what I am talking about. It will be a big undertaking for an "olde fucke" like me. I would like to re-do everything and remove the roll bar cross bar for the for the racing seatbelts so I can replace the racing buckets with something that reclines with side boltsterers and real padding to make my back and "roids" happier. Then of course there is the full wheel tubs and wrinkle wall slicks and wheelie bars, tunnel ram and 7" full pro Sox & Martin scoop install, along with the Borgeson power steering and a Flaming River tilt steering wheel. Then perhaps an overdrive tranny and cruise control to ease the cruising RPM's a tad! I don't ask too much,do I ??? LOL
                           
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