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switches or resistors?

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AMC Nut
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    Posted: Aug/14/2019 at 2:04pm
Finally got the electrical squared away on the '72. Blower motor works great, but at the switch I get no low speed, and medium and high are both just high speed.  This car has AC and the relay out in the engine bay with a direct feed from the batt.  Havent attacked anything with the multimeter yet.  Would you guess the resistor or switch to blame for speed issues?

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C
72 Javelin SST P code 360/auto/AC/rear defrost /Go Pack/Polar White w blue cord interior.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Heavy 488 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/14/2019 at 7:37pm
As long as you have a meter, just go for it. After pages of replies you'll still have to check it for a definitive answer.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Sep/30/2019 at 6:22am
Sounds like you're missing the speed resistor pack, or it's not connected. AC cars have a single speed motor. The switch directs power through a resistor pack for the two lower speeds. Sounds like someone bypassed or removed the resistors and went straight to a relay, so only one speed (high). I believe the 72 resistor pack would be mounted on the outside of the heater fan housing. The 72 TSM only shows the 10-80 series housing. Later cars had the resistor pack INSIDE the heater fan housing. It would screw onto the outside and have three terminals (one for each speed, motor will have a separate ground), with the actual resistors inside the housing so they would get some cooling from air moving in the fan box, not just under hood air like the older (and 72 10-80) cars. You can use any resistor pack from just about any car, but the packs designed to mount the resistors inside MUST be mounted that way or the resistors won't last long. Most modern cars are that way, and the 72 Javelin might be.
Frank Swygert
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