A/C for 81 Brat

[Lachlan]

I was thinking about pulling one of the many, many 2nd gen A/C systems laying around the pick n pull for my 81 brat. A couple of things were weighing on my mind, though:

 

1. What tells the compressor clutch to engage? I assume there is some electrical connection that I wouldn't have.

 

2. Will the evaporator fit in my dash hole?

 

3. Is it hard to convert to R134a?

 

Thanks to you A/C pioneers!

[superbrat84]

if you look at your dashboard it should have a sticker saying that this car has the option for a/c. so it should be pretty straight forward.

[Dogbone]

I was thinking about pulling one of the many, many 2nd gen A/C systems laying around the pick n pull for my 81 brat. A couple of things were weighing on my mind, though:

 

1. What tells the compressor clutch to engage? I assume there is some electrical connection that I wouldn't have.

 

Specifically, you'd either have to consult a shop manual or dissect a system from a donor vehicle or pick the brain of an expert.

 

But generally speaking, the compressor is "told" to engage when you push the A/C button on your dash. This activates a relay that closes, which sends 12volts to your A/C compressor clutch.

 

In series with this particular circuit to your A/C clutch is typically a high and low pressure switch (on my Loyale it this is combined as one switch called a "trinary switch") that will open, disengaging the clutch, when either your refrigerant charge is too low or too high.

 

Also in series with your A/C clutch 12 volt circuit is a temperature sensor that will open when it detects your evaporator is too cold. This prevents the evaporator from freezing, and is responsible for the normal COMPRESSOR CYCLING that occurs during normal operation.

 

2. Will the evaporator fit in my dash hole?

 

The real experts will have to answer this one.

 

3. Is it hard to convert to R134a?

 

No.

 

Despite what rumors you may or may not have heard, an R12 system will not explode or warp time during 134a conversions.

 

The biggest concern is the oil in the system, the oil that lubricates the compressor's moving parts. In your A/C system, this oil needs to be in suspension in the refrigerant to circulate and keep the compressor lubricated and happy.

 

R12 systems use mineral oil.

 

R134a systems use PAG oil.

 

Mineral oil will NOT combine with R134a, and therefore will not lubricate the compressor properly. The oil will typically puddle in a low point, and the compressor will eventually oil starve and fail.

 

Evacuate the system, and put in the proper amount of PAG oil, and you will be fine.

 

As well, you'll want to replace your drier, and put in the green R134a o-rings at the hose connections, and of course the R134a fittings on your charging valves.

 

 

Thanks to you A/C pioneers!

 

Good luck.

Edited July 7, 2011 by Dogbone

[mdjdc]

If you are interested, I have an entire aftermarket/dealer install system. It is new and has all of the parts in the box. PM me if you are interested and we can talk turkey.

 

Mike

[superbrat84]

i have looked at my system installing the evaporator is pretty straight forward just have to make sure it seals (might have to get cover for evaporator) i would get freeze 12 at o reilly autoparts it is as close to r 12 as you can get. as long as you're bogging the car down you might as well have it get as cold as you can get. in fact you can buy full r12 cans off ebay. my system is still running r 12 and gets as far down as 35 degrees F

[eulogious]

I would just use r134a. Freeze 12 is a blend of r134a and some HCFC's. It's 80% r134a and 20% HCFC-142b to be exact. And it's getting harder to source locally, while r134a you can buy in a can almost anywhere.

 

People knock r134a for not being as cold, but that is a misconception really. It just doesn't absorb heat as well as r12, so when people convert their system to r134a it doesn't get as cold because the condenser needs to be a bit bigger to dissipate the heat better, therefore cooling better.

 

Last time I got into my parents 2008 MDX with r134a, that car was blowing ICE cold. So to say that r134a won't cool as well is really not a true statement, since most cars on the road cool just fine. It's the conversions that don't cool as well, and that's because you just need more area on the condenser to make up for the lack of heat absorption in r134a. Upgrade your condenser when you do the conversion, and you won't notice any difference between r12 and r134a most likely anyways.

Edited July 15, 2011 by eulogious