Mystery knob behind / under glovebox

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Claytonk

Claytonk

Joined
May 17, 2026
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While trying to troubleshoot a blower motor not working I found this knob under the dashboard behind the glove box it's tied into a 30 amb relay and seems to almost have a thermocouple coming out of it with a knob that you can turn on the bottom ? I solved the blower motor issue it was a bad blower motor relay, but what is this knob for?

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Kill switch?
 
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It's an adjustable knob, so I wouldn't think kill switch. Anything is possible though I guess. It also has a solid wire coming out of it like a temp sensor of some sort.
 
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Pighead said:
Is there an electric radiator fan?
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🤔, I didn't think so , but maybe there's one I haven't seen yet if it's in front of the radiator? I just bought this truck so it's new to me. I will check it out.

This 60 is equipped with the York AC compressor, and from my research this was probably Port or factory installed A/C when it came in from Japan. I was wondering if it had something to do with that possibly?
 
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Spike Strip said:
It probably acts as the AC amplifier and tells the compressor when to turn on and shut off according to the temperature in the evaporator.
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That’s what I was thinking, hard tube looks like a temp sensor maybe, knob allows you to set the compressor kick on temp.
Just a WAG.

Where does that hard line run to?
 
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Slow kill switch…
 
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It seems to go into the top of this box
And after further inspection the red wire goes to a 30 amp relay and the black wire goes to the AC compressor

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Spike Strip said:
Yeah, it's a rheostat to control the cycling of the A/C compressor so the evap doesn't freeze up. If your AC is working fine, leave it alone. If you need it colder, adj in small increments to see the effect.
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AC doesn't work but of course being the person I am I twisted it in all directions now I have no idea where it was set at
 
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I had this exact same knob in my 86 HJ60. It was also connected with same wires and relay like yours. I pulled all of the wires and relay because I changed the AC box with late model evaporator because it had this older copper tubed evaporator. And it didn't have some of the AC hoses, so I decided to overhaul the whole AC system with late model parts. I have managed to source all the related parts like evaporator, drier, hoses etc. However I can not sort out the wiring difference between late and early model AC because my HJ60 AC factory wiring and connectors are different and don't plug up with the late parts. The blue AC knob is not lighting up and I can't trace the black wire coming from the AC compressor. You showed in the pic pointing the black wire from the knob goes to the compressor. How were you able to trace it and can you confirm it. Because that will be great help for me find the black signal wire coming from the compressor.
Thanks,
 
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Interesting...looks like a custom evaporator box was made and they completely bypassed the A/C amplifier with this thing. I think it's some sort of homebrewed A/C job considering they installed a York compressor and a different expansion valve on the firewall instead of inside the evap box.

I've also never seen A/C lines held on with worm clamps before....
 
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