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DIY-AC install in an old car.

Cassius on Sat May 19, 2012 4:14 AM User is offline

Year: 1971
Make: Opel
Model: Manta
Engine Size: 2400cc
Country of Origin: Sweden


I'm researching putting an AC-system into my 1971 Opel Manta. I've planned to take a roadtrip through europe next summer or maybe the summer after that and with the interior being black an AC would be nice, therefor I'm looking in to the size of the project and how it's supposed to work together.

The mechanical aspects of the build isn't something I'm worried about. Fitting it to the car will probably give me a couple of grey hairs but shouldn't that big of a problem. I know the parts I need is a compressor, a dryer, a condenser, a evaporator, an expansion valve, a pressure switch and an On/Off button of some kind. Did I forget something? So like I said, that's not what I think is the difficult part really. And I've got a good grip of the overall function of the system, which is the same as a fridge or heatpump, I'm also fully aware of the costs

No, the thing I'm looking for help with is the coolness-control!

I've learned of one way to adjust this, and rear a little about two other's that I have my own theories about.

First. When the AC is activated, it blows "all out", full function and how cool the air getting into the car gets is controlled by adding heat with the normal heating system.
Second. To control the flow of the AC system, the compressor works more or less hard to adjust how cool the air blowing into the car is. This seems like the most complicated system?
Third. By adjusting the expansionvalve the pressure difference between low and high side can be adjusted and there by also the cooling effect. Now this one actually feels like something that could be done!

The thing is, I'm actually happy with having an On/Off system, but if an adjustable system can be built without it getting way complicated with electronics (I don't like electronics ) it might be worth giving it a try!

But would a system that adjusts the expansionvalve work? And what additional parts would I need? Is it something like this: that I'd need to adjust the expansionvalve?

I can't find any good info on the net from others that have done this so I hope you can help me out Most threads out there are about people taking complete systems from donor cars of the same brand and model. I could do that, but my car only had AC in a couple of cars that were sold in the states, and I'm in Sweden so finding one will be extremely difficult! And putting together a "custom" system in my mind should be too hard either

Dougflas on Sat May 19, 2012 6:10 AM User is offline

The expansion valve is not the item that adjusts the temperature of the system. Actually the expansion valve (TXV) is set to a predetermined superheat valve and does not change. The TXV actually controls the temp of the evaporator. In order to control the temp of the AC output, you'll need a thermostatic switch. This switch can be adjustable or preset. The sensing bulb is usually stuck into the evaporator. The switch contacks will open the voltage supplied to the compressor clutch. I would suggest that you do an internet search on some of the add on systems available (could be for any vehicle) and study the wiring diagram to learn the operating set up.

And yes, the part you are listing a link to will do exactly that.

Edited: Sat May 19, 2012 at 6:12 AM by Dougflas

Cassius on Sun May 20, 2012 4:00 AM User is offline


So in short, the termostatic switch when turned down to a lower temperature makes the compressor "start and stop" so that it only maintains a certain flow that's enough for the temp desired?

Sounds easy enough I'll take a look at some aftermarket systems and see if I get any smarter

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