Questions for A/C Gurus

[ToughOldFord]

Okay, as mentioned in another post I'm building an A/C system for my old Plymouth. I bought one of these as a start:

http://cgi.ebay.com/ebaymotors/New-A-C- ... dZViewItem

In my bump I reassembled the system using used parts from a junk yard, mainly because they were easily available and my truck still had half the system in it. But I still don't have the bugs worked out yet.

With this car since I'm starting from scratch I'd like to use all new components, (except compressor mounting brackets.), and I'd like to do it right. I feel have a fair understanding of A/C systems, but hardly a professional. I have been reading up on A/C's lately and wold like to top it all off with input from guys that know.

1) Do any A/C components need to be matched? Compressor/dryer/evaporator/condenser? If so, how do I determine what I need? Or are the parts pretty much universal as long as you can hook then together?

2) I was reading that "serpentine" style condensers are better than the parallel ones as they can be efficiently flushed. Is the the only real benefit? Seems the parallel ones are the easiest to find.

3) How will I know what pag oil to use? Is this determined by what compressor I use? Or is the universal stuff fine?

3) Will I have to have custom lines made? Or does someone sell various assortments that I can pick from?

4) Anything, else I should know that I haven't asked? Don't want to overlook anything. I did buy a quality manifold and gauge set so I won't be doing the add a can 'till it works okay routine anymore. I'll be picking up a vacuum pump soon too.

TIA!

[kid]

Evap, condenser coil and compressor must match for best cooling, Line size smaller on high side larger on low side. Not the same like in car systems really makes it do better.

Even high end House units use parallel ones. The oil matches the compressor requirements. You need a TXV (Temperature expansion valve). It goes in the high side and and checks the temp on the low side and adjusts the orifices size. The dryer goes in the high side and can be as big as you want.

[ToughOldFord]

Thanks Kid, that's the kind of info I'm looking for.

So, is the line size the only matching I'll need to do for the evaporator, condenser, and compressor? Looking at the unit now I can see it is made with the small size on high side and large on the low pressure and the EV is already installed. So as long as I match my sizes I can run whatever compressor and condenser? Or is there anything else I should match?
Good to know about the parallel condensers too, I'm not finding a lot of availability on the serpentine style.

Thanks again.

[kid]

Line size is critical to maintain the Super Cool ratio. Use what it has and see what compressor they recommend. Super cool takes into account the amount of charge the system has. You compare the condenser inlet and outlet temp to the Evaporator inlet and outlet temp. But to do SuperCool charging you need a Supercool Chart and a wet and dry bulb Thermometer.

[ToughOldFord]

Thanks for the info Austin, I'm absorbing it all and will put it to use when I put this system together. My goal for this one will be next summer though, the old car hasn't been on the road for some years so A/C is just one of the many things I have to do to the ole girl. So right now I'm just gathering info and parts.

What do you guys think of freon filters? Worth the bother?



And I've never seen a dryer like this before, looks a lot like that filter:


Car Care part # AC2490.


Any idea? Wouldn't you have to mount that horizontally? Should I just stay away from it?

[ToughOldFord]

I've seen the dryers called filters, but these are something different, they're just very small filters that you add to the system.
Here's Supercool's

http://cgi.ebay.com/ebaymotors/R-12-R-1 ... enameZWDVW

[kid]

It is the same thing. A filter filters out water and and compressor carbon build up. To get rid of the water your filter has desiccant inside of it that absorbs and hold the water.

When my vacuum pump pulls for a long time it usually does not indicate a leak but water in the system.

[dablack00]

That filter is only for debris. The only time you are going to have debris is if you didn't flush your lines before installation or if your compressor dies a horific death. Either way, you are going to have to go back and flush your lines anyway, so I don't see a point in it. Just flush your lines and you should be good to go. There is a flush gun you can get that you put the solvent into, and pressurize the pot. Then you can spray the solvent through the lines. I think you can flush a condensor and evaporator too, but I need to check. You can't flush your filter/drier.

[ToughOldFord]

Couple more A/C questions.

1) Way back when I first charged an A/C, (ancient late 1980's as I recall. We were still buying the good stuff, R-12, for .69 cents a can at the local department store), the procedure said that after you open the can of freon to the system to run the engine at 2,000 RPM for a couple of minutes. I've never seen this said since. Is there a point to this? Is it old school for old compressors??

2) Also, the procedures back then said to empty the first can in the upside down position for the liquid freon then the rest in the upside position for the gas. This also isn't mentioned anymore although I've been doing it for many years with pretty good success. Also my Cherokee will not take any freon unless the can is upside down. Always been like this in the 6 years I've owned it. It used to leak a can or or a year and that's how I've done it every time and AC would work great until it leaked off. Last couple of years it's gotten worse so I just now finished putting a "new" compressor in, (the old one was leaking at a seam, I used the dye to find the leak), and this time I had the manifold and gauges to do it correctly, but it was the same thing, it would not take freon unless I held the can upside down. System is charged and working great now, but what gives???

[rjewkes]

i thin some brands only charge as a gas and some only as a liquid. som can go either way.

[Wes]

I myself avoid Pag oil, I use ester oil in both r12 and r134a systems. Pag oil is a nasty carcinogen, esp used.

[kid]

Couple more A/C questions.

1) Way back when I first charged an A/C, (ancient late 1980's as I recall. We were still buying the good stuff, R-12, for .69 cents a can at the local department store), the procedure said that after you open the can of freon to the system to run the engine at 2,000 RPM for a couple of minutes. I've never seen this said since. Is there a point to this? Is it old school for old compressors??

We don't run them during the initial charge anymore as there is no oil in a rebuilt system to lubricate the pump. It leaked out with the Freon.

2) Also, the procedures back then said to empty the first can in the upside down position for the liquid freon then the rest in the upside position for the gas. This also isn't mentioned anymore although I've been doing it for many years with pretty good success. Also my Cherokee will not take any freon unless the can is upside down. Always been like this in the 6 years I've owned it. It used to leak a can or or a year and that's how I've done it every time and AC would work great until it leaked off. Last couple of years it's gotten worse so I just now finished putting a "new" compressor in, (the old one was leaking at a seam, I used the dye to find the leak), and this time I had the manifold and gauges to do it correctly, but it was the same thing, it would not take freon unless I held the can upside down. System is charged and working great now, but what gives???

When the can is upside down you get the liquid first. If the system is empty and under vacuum the liquid flashes off the vapor instantly. Once the system has a little charge the liquid will stay that way and a slug of liquid hitting the compressor will break the pump. (If the pump is running) So on partial refills or topoffs use the can right side up. I have done enough that I learned to tip the can and let liquid in but I listen for the sound of the liquid converting to gas and if I don't hear it I stop tipping in the liquid.

Don't run the compressor until the system is half full.

When I build the system in Yellow Brute I am going to make it like a modern system with R-134, Sight Glass, Filter and low pressure cutout and Wide open throttle cutout.

[kid]

The Blue cap is your low side service port and the Red is the high side. The silver caps are for the valve stems that have to be opened on the Supply side to fill and the high side to test.

Your Freon can might not have had enough internal pressure to fill the system.

[Fake Name]

When I build the system in Yellow Brute I am going to make it like a modern system with R-134, Sight Glass, Filter and low pressure cutout and Wide open throttle cutout.

Something else to consider (although you probably already thought of it)- if you're going with electric engine fans, be sure to install an over-pressure switch to kick the fan in. After installing my Classic Air System, I was lucky enough to take it to a AC specialist for the evac/fill. He caught the problem right away. It's possible for the AC to get hot without the electric fan (engine temp switched) running. No fan=no cooling for the AC condensor=high pressure and possible seal/compressor failure.

Conventional fans are not a problem, as they are always turning with the engine.

Now, back to the original problem....


fn

[kid]

Actually I tie my 10" fan to the AC Pressure switch and to a 190 degree thermostat.