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Source/Alternate for A/C Thermostat? ['79 Spirit]

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Scrappy View Drop Down
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    Posted: Jul/20/2021 at 5:20pm
Y'all,

The arm on the A/C thermostat in my '79 Spirit has broken off and I'd like to replace it, instead of bypassing it (it's listed as "optional" in the service manual).  It appears to be effectively impossible to reattach, plus I have no idea what position it was in when it broke off.  It's really not surprising that it broke off, since the stiff operating wire pushes at an angle to the plane of rotation.

I'm not having any luck finding one of these, no matter what combination of markings I search on, or looking up parts for a '79 Spirit.  Does anyone know a currently-available part number for this or an alternate that's easily installed?

Thanks,
Shawn







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Post Options Post Options   Thanks (0) Thanks(0)   Quote amcfool1 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2021 at 12:46pm
Hi, I am looking for one of these as well, though for an 84 Eagle. Any luck?
thanks, gz
george z
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Scrappy Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2021 at 2:07pm
Originally posted by amcfool1 amcfool1 wrote:

Any luck? thanks, gz

Unfortunately not, GZ.  I've removed it and installed a jumper, so it'll essentially operate like the version without the thermostat option.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nickleone Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2021 at 2:47pm
Spot weld or tig weld it together.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6PakBee Quote  Post ReplyReply Direct Link To This Post Posted: Oct/19/2021 at 4:13pm
It looks like an adjustable temperature switch.  What does it use for temperature sensing, a coil, a thermal bulb, ???
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Post Options Post Options   Thanks (0) Thanks(0)   Quote amcfool1 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/22/2022 at 5:33am
hi, it uses a probe set into the evaporator.   gz
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Post Options Post Options   Thanks (0) Thanks(0)   Quote CamJam Quote  Post ReplyReply Direct Link To This Post Posted: Jul/24/2022 at 7:42am
Not sure if there is a separate thermostat in that circuit to keep the evaporator coils from freezing, but if not you might want to add one. Either that or you'll have to periodically turn the compressor whenever the coils start freezing over. This sort of thermostatic switch would automatically accomplish that for you.  It's like the Ranco switch found in most AMC's, but preset rather than adjustable. 

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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/25/2022 at 4:33pm
You may be able to re-attach the control lever by using JB Weld, possibly by some form of welding or soldering or possibly have a jeweler silver solder it.
As for knowing what position is correct to re-attach the arm to the shaft, try this:
These switches are temperature sensitive and operate in a click on and click off manner to switch the a/c compressor on and off. What you want to do is determine the click on or click off point. You can do this by putting the entire switch with the sensing tube in your refrigerator. You want to set the click off position at just above freezing, say 34 to 36 degrees. This is a typical temperature for a refrigerator and you can always use a thermometer to verify. Put the switch in the refrigerator so it will get cold.
Using a typical ohm meter or battery operated test light connected the the cold switches contacts verify the click off point (switch contacts open) by turning the control’s shaft to that point. Do it quickly as these controls with the sensing tubes react rather quickly. I suppose the ideal way would be to wait until winter and the outside temperature is in the 34 to 36 degree range.

Once you’ve set the switch to the click off point the shaft is in the approximately correct position. Now you can position the control lever that broke off in the full cold position and place it back on the shaft. Don’t move the shaft and make a mark to indicate where the lever, set at full cold must be reattached.

Assuming your a/c system works by compressor cycling to control temperature this should work to get you by.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote nickleone Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2022 at 5:36pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Scrappy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/25/2022 at 7:47pm
Originally posted by CamJam CamJam wrote:

Not sure if there is a separate thermostat in that circuit to keep the evaporator coils from freezing, but if not you might want to add one. Either that or you'll have to periodically turn the compressor whenever the coils start freezing over. This sort of thermostatic switch would automatically accomplish that for you.  It's like the Ranco switch found in most AMC's, but preset rather than adjustable.

https://www.amazon.com/dp/B07CZSKB8C?psc=1&ref=ppx_yo2ov_dt_b_product_details


Originally posted by nickleone nickleone wrote:

How about this:
https://www.ebay.com/itm/384964444252?hash=item59a1ab405c:g:gRwAAOSwCi1is2So

Thanks, fellas -- both of those look like good options. CamJam, no, there is not a separate thermostat in the circuit.

Originally posted by george w george w wrote:

You may be able to re-attach the control lever by using JB Weld, possibly by some form of welding or soldering or possibly have a jeweler silver solder it... Once you’ve set the switch to the click off point the shaft is in the approximately correct position. Now you can position the control lever that broke off in the full cold position and place it back on the shaft. Don’t move the shaft and make a mark to indicate where the lever, set at full cold must be reattached.

Thanks for the extensive writeup, George!  I've kept all the parts, so if I decide to go for full original functionality, I'll go about it that way.  I'd use the refrigerator method, though -- I don't want to wait around for the exact temperature outside. :)
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