Parkomat System

[Andy_napco]

I just joined the forum, thank you for having me. I have a 1955 GMC truck as equipped with a Pontiac V8. I’d always wanted A/C but wanted to stay true to the era.

I’ve collected and refurbished all the under hood hardware from a Pontiac car equipped with factory A/C. I have a Parkomat unit in the cab. I’m trying to understand the operation of the Parkomat.

Does anyone have any information on how it works mechanically. There is a fan speed dial with Off, High, Medium, Low in a clockwise arrangement. Then a series of buttons with the following settings left to right: Off, a series of 3 unlabeled push buttons and then Precool (left to right). Lastly on the far right a thermostat control dial starting with defrost, then 1, 2, 3, 4, 5, 6, 7, 8, 9, 0 then manual.

It’s hard to tell if the choices are independent of each other and the user opts for the buttons or the thermostat dial to choose an a/c temp. Or do they all act in some integrated fashion?

Any help greatly appreciated, an original manual would be the best. I’ll try and load some photos.
Thanks?
Andy

[JohnHere]

As far as I know, the Parkomat system was primarily designed to cool the sleeper cabin of a tractor/trailer without the engine running to minimize noise and fuel waste. The compressor, I believe, was electrically driven by an integral motor and powered by a lead-acid battery. Other than that, the refrigeration system was about the same as one would expect, except for the refrigerant, which in 1955 would have been R-12.

Your pictured unit shows only the evaporator and controls. I think the rest of the system was located either in the tractor's engine bay or mounted on the sleeper's roof.

I suppose you could mount a belt-driven compressor on the engine and drive the compressor in the usual way, and then operate your evaporator and control unit inside the truck, similar to how the Mark IV units were configured.

The controls are as follows: First, the Manual Blower Control turned Off the blower, and then turned it on to Hi, Med, and Low; next, the series of five unlabeled pushbuttons controlled which vent(s) the air came from, and selecting the Precool button would direct ambient air to, I think, all six of the vents; lastly, the Thermostat Control regulates the temperature of the air from warmest (Defrost) to coldest ("0" or zero).

Pretty clever design, although the original system was limited obviously to how long the battery charge lasted.

[Andy_napco]

My goal is to run it off a belt driven compressor, I’ve plumbed all the lines but have not yet tried to draw a vacuum and/or charge the system. Taking my time so I don’t make a co$tly mistake.

In your experience would the hot lead be the black and operate the fans speed control as well as the buttons and thermostat? They’re all interconnected on the back of the panel.
The orange lead with an inline fuse would be for the clutch on the compressor I’m thinking.

I’ve attached a photo of the wiring on the back side of the panel.

[JohnHere]

My goal is to run it off a belt driven compressor, I’ve plumbed all the lines but have not yet tried to draw a vacuum and/or charge the system. Taking my time so I don’t make a co$tly mistake.

A belt-driven compressor should work.

If you haven't already done so, I would remove the TXV, inspect it, and if it passes inspection, clean it up. It's probably one of a kind. Also, I'd recommend thoroughly flushing the evaporator coil. Never know what might be crawling around inside.

In your experience would the hot lead be the black and operate the fans speed control as well as the buttons and thermostat? They’re all interconnected on the back of the panel.
The orange lead with an inline fuse would be for the clutch on the compressor I’m thinking.

I'm unsure about the wiring, and I can't tell from the photo. It appears, though, that everything is hooked-up together, as you said, and gets power from the orange inline-fused wire. By chance is there a 15-amp or 20-amp fuse inside the fuse holder?

Since all the controls appear to be powered by direct battery voltage, it looks like the Thermostat Control would power the clutch and, in turn, operate the compressor, turning it on and off according to the set temperature "read" by the capillary tube. For safety's sake, I would also install at least a binary switch somewhere on the high side of the system (usually on the R/D). Or, if you prefer automatic fan control, install a trinary switch.