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Old 11-08-2019, 02:05 PM
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Towtruck Towtruck is offline
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Air Conditioning System - 81 J10?

I removed the original factory AC from my truck about ten years ago, and am in the process of reinstalling the same system (with R132 hoses and a replacement compressor). I think I have all the parts, but don't see a typical hi/low pressure switch with wiring that would cycle the compressor clutch. The wiring diagram for the early AC does not depict a switched clutch....so I guess the compressor runs continuously when the AC is switched on. I'm just double checking with the experts to be sure I'm not missing something. I'm obviously not an AC guy. Thanks.
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J10 - Body channel (3 inch drop @ front); dechromed; shaved side parking lights, antenna, and hood trim bar. Ford mirrors, roll pans, side exhaust, 16 inch wheels, custom dash, new interior, Edelbrocked 360, HEI, T18/208 (J20), rear disk brakes, goose neck and bumper hitches.
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Old 11-08-2019, 08:35 PM
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Mikel Mikel is offline
 
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Quote:
Originally Posted by Towtruck
I removed the original factory AC from my truck about ten years ago, and am in the process of reinstalling the same system (with R132 hoses and a replacement compressor). I think I have all the parts, but don't see a typical hi/low pressure switch with wiring that would cycle the compressor clutch. The wiring diagram for the early AC does not depict a switched clutch....so I guess the compressor runs continuously when the AC is switched on. I'm just double checking with the experts to be sure I'm not missing something. I'm obviously not an AC guy. Thanks.


Someone more knowledgeable than me will correct me, but I think it's the thermostatic switch (the temp knob in the controller) that does that.
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Old 11-09-2019, 07:45 AM
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Towtruck Towtruck is offline
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Makes sense to me...thanks.
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J10 - Body channel (3 inch drop @ front); dechromed; shaved side parking lights, antenna, and hood trim bar. Ford mirrors, roll pans, side exhaust, 16 inch wheels, custom dash, new interior, Edelbrocked 360, HEI, T18/208 (J20), rear disk brakes, goose neck and bumper hitches.
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Old 11-11-2019, 08:19 PM
'89_Wagon '89_Wagon is offline
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I can't speak to early FSJs, but my '89 has 2 points that would turn the compressor off.

Low pressure switch: This is a fail safe in case refrigerant escapes the system, which would prevent the compressor from burning out. Mine is wired in-line with the clutch switched 12+ wire.

Thermistor: A thermistor probe sits in front of the AC evaporator core, with resistance varying with temperature. A module in my '89 reads the resistance and cycles the compressor as needed. I imagine something more analog would replace the module in your earlier FSJ.

I've heard the thermistors are hard to find, but my FSj manual does provide the resistance chart if you need that.
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Old 11-12-2019, 08:10 AM
rocklaurence rocklaurence is offline
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Nope, there's a module with a switch that sets inside the plenum that has a Temp' tube with it. It senses the temp' and cycles the compressor. Your AC control panel should have two switches: Fans Speed / Temp
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Old 11-13-2019, 08:57 AM
'89_Wagon '89_Wagon is offline
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Quote:
Originally Posted by rocklaurence
Nope, there's a module with a switch that sets inside the plenum that has a Temp' tube with it. It senses the temp' and cycles the compressor. Your AC control panel should have two switches: Fans Speed / Temp

This seems like an option for the later GW in case the board blows out in the module or a source for thermistor probes can't be found. Is this sort of like what the earlier FSJs use? The probe would sit in front of the evaporator core?

https://www.summitracing.com/parts/fss-35845?rrec=true

Oddly enough, my wife's Passat AC stopped blowing air during a long drive but the blower was definitely spinning. After turning the temp UP, air started coming out again. The problem, ice had formed on the evaporator core. The module should have prevented that.
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Old 11-14-2019, 07:46 AM
rocklaurence rocklaurence is offline
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Yep, that looks like it. I didnt know that anyone made a replaement.
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Old 11-14-2019, 09:02 AM
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Towtruck Towtruck is offline
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Since the recent cold snap slowed me down with this reinstallation, I think I'll add a high/low switch to the old style system. Seems like a worthwhile safety feature, and I need to have that particular hose modified for a better fit anyway. I guess it would be wired in series between the fuse and compressor clutch?
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  #9  
Old 11-15-2019, 05:44 AM
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Locked and Loaded Locked and Loaded is offline
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I also have an 81. But with a 258. I added a low pressure switch to my drier years ago.
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Old 11-15-2019, 10:52 AM
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letank letank is offline
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Quote:
Originally Posted by Towtruck
I removed the original factory AC from my truck about ten years ago, and am in the process of reinstalling the same system (with R132 hoses and a replacement compressor). I think I have all the parts, but don't see a typical hi/low pressure switch with wiring that would cycle the compressor clutch. The wiring diagram for the early AC does not depict a switched clutch....so I guess the compressor runs continuously when the AC is switched on. I'm just double checking with the experts to be sure I'm not missing something. I'm obviously not an AC guy. Thanks.




the OEM was a low pressure switch positioned next to the battery. In most newer system you can swap a binary switch, Low and High pressure combo, they are often part of the filter/dryer. There are even triple switch "trinary".... to activate the condenser fan
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