Mystery knob behind / under glovebox

[Claytonk]

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?

 

[dogfishlake]

Score some back alley R-12 and fire that baby up!

 

[aztoyman]

@Spike Strip nailed it. It's a manually adjusted thermostatic switch. This is what was typically put on old school A/C under dash units on vehicles in the 50's, 60's and even today on universal under dash units.

The thermal bulb "senses" the evaporator temp. The knob lets you adjust the point that the switch opens and cuts off power to the compressor clutch. So like mentioned, it does what the A/C amplifier does on most Toyotas.

If you live in a humid area, your evap could "possibly" freeze up if it's set at the coldest position. It's mainly to adjust how cold your air gets. Kind of like the knobs on our dash that might show from blue to red for cold to warm. An analog version.

Usually turning it counter clockwise is coldest but you'll have to try it to find out for sure. You didn't hurt anything by changing it from where it was set.

I have 66 Mustangs with this setup that still work. You can still go to auto parts stores and buy universal ones if yours is bad. They are so basic that they usually last forever. Breaking the tube is the typical failure. Corrosion inside can usually be cleaned out. Pretty reliable units. So are the York compressors. I think they can be rebuilt and many people want them for onboard air compressors.

 

[Claytonk]

Is there an electric radiator fan?

Negative, no electric radiator fan

 

[Claytonk]

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....

From what I understand this is a dealer /port installed accessory on early rigs.
I've seen pictures of others with the exact setup

 

[Claytonk]

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,

It comes through the firewall and right to the knob I was talking about

 

[george_tlc]

Yep, it's basically and old school thermostat for the AC. My 1980 patrol in oz that had dealer installed AC has a similar thing. Set & forget. Of course the old patrol's AC is long dead and disconnected.

cheers,
george.

 

[Lead Head]

Definitely "custom". I'm guessing there was a certain dealer/importer who was ordering them without AC and adding it themselves. The plastic that box is made out of looks like one of those "thermoform" plastics like Kydex, that you can easily warm up and re-shape. That knob is just a temperature switch to keep the evaporator from freezing. The hose clamps holding the hoses onto the compressor is pretty wild. Definitely not suitable for R134a.