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Blower Runs Constantly/Low Defroster Air Flow

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george w View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote george w Quote  Post ReplyReply Direct Link To This Post Posted: Jul/12/2021 at 4:45pm
Doesn't your car use a rotary temperature control switch to the far left of the dash ? The switch has a Desert Only position ? This switch must be turned fully CCW past the detent to shut the low speed of the blower off.
Long time AMC fan. Ambassador 343, AMX 390, Hornet 360, Spirit 304 and Javelin 390. All but javelin bought new.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nashman50 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/12/2021 at 8:02pm
Yeah it does for the air conditioning. It seems to be the whole way off but I’m going to clean the switch and make sure too. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote george w Quote  Post ReplyReply Direct Link To This Post Posted: Jul/13/2021 at 10:26am
The "switch" portion of the thermostatic cooling temperature control is attached to the front of the control body. There's a flat circuit board with a circular contact surface and a movable contact that feeds the low speed setting of the main blower switch up on the HVAC controls as soon as the temperature control knob is switched "on" by being turned CW off the detent. There's a single blue wire pigtail that leads from this switch up to the main blower switch. Disconnect this wire and see if the blower shuts down. The switch wiring is show in the All Season Air Conditioning section of the factory TSM. Perhaps the switch was miswired as there are other wires going to the thermostatic portion of the control as well.   
Long time AMC fan. Ambassador 343, AMX 390, Hornet 360, Spirit 304 and Javelin 390. All but javelin bought new.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nashman50 Quote  Post ReplyReply Direct Link To This Post Posted: Aug/14/2021 at 10:23pm
Turns out that it was the AC thermostat.  We tested it and it was drawing a lot of power and not turning off.  Replaced the switch and everything works well.  Thanks, everyone!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Aug/16/2021 at 6:41am
I need a new temp switch for mine. Don't have the problem you have, it just doesn't do anything. The compressor comes on and stays on, I think, doesn't appear to cycle. Just as well for the hottest parts of the summer when it's really needed. The factory AC doesn't cool a wagon that good. Keeps you from sweating, but that's about it. Oh, I'm in central South Carolina -- hot humid summers! Would be wonderful in Wisconsin!!
Frank Swygert
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Post Options Post Options   Thanks (0) Thanks(0)   Quote javtopgun Quote  Post ReplyReply Direct Link To This Post Posted: Sep/20/2021 at 6:52pm
Not any more Farna .. read the news ... Minn. set all kinds of new heat records this summer .. over 100 a few more than a few times ... Nowhere safe .. LOL . Come join me here in vegas ... U with week air and me with no air !! quite a pair .. lol !!
1968 Javelin SSt 343ci semi restomod .
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Post Options Post Options   Thanks (0) Thanks(0)   Quote javtopgun Quote  Post ReplyReply Direct Link To This Post Posted: Sep/20/2021 at 6:57pm
I think that would be your high pressure switch bad .. and as i recall your compressor is running hot by not cycleing and may be causing the cool down rate  problem . 
1968 Javelin SSt 343ci semi restomod .
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Post Options Post Options   Thanks (0) Thanks(0)   Quote javtopgun Quote  Post ReplyReply Direct Link To This Post Posted: Sep/20/2021 at 6:59pm
or low pressure switch is shorted also will not let compressor to cycle .
1968 Javelin SSt 343ci semi restomod .
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Sep/21/2021 at 5:55am
I'm not having any overheating issues now that I have the larger radiator and better fans. My hybrid system doesn't have a high or low pressure switch (or a trinary combo high/low switch like newer cars). The 63 AC system didn't have it, and I didn't install one when I had the new hoses made. The switch is a safety in case you have a leak and continue running it. The old York compressors had an oil sump and really didn't need it. The Sanden style compressors get oil through the refrigerant and can burn up if not enough refrigerant in the system to carry oil, therefore the need for a switch. I just turn it off if it's not cooling... I am the switch! It's not a big deal to install a switch, but since I'm the only one who drives the car it's not a big deal without it -- not as long as the AC system is in good working order anyway. A less attentive driver, or one who doesn't know cars/this car very well would want one for sure.
Frank Swygert
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