I've been considering installing the VIR elimination kit do upgrade my A/C. Does the kit do away with the old-style POA valve completely? Would there be any advantage to using the 77L-79 two-tube evaporator with the kit, rather than the three-tube 73-77E evaporator? Would it even be possible to use the later evaporator?

These older A/C systems give me a headache...

 

Second question - is there any way to modify the 77 HVAC vacuum controls so that the hot-water shutoff valve cuts off flow in every A/C position, not just "MAX?"

 

The four main components of the A/C system are the pump, evap, condenser and some type of freon throttling device. In the POA system, there is the added complexity of the POA valve that regulates the evaporator pressure, and a TXV (thermal expansion valve) that throttles the freon and takes it's throttling queues from the evap's outlet temp.

The expansion tube system uses a fixed orifice to throttle freon, and along with a low pressure switch that cycles the pump, it maintains the ideal evap pressure. I converted my A/C to the 78-82 system using the year specific evap and never looked back.

The old POA system always froze up on me during humid days, and instead of learning exactly why the added valves and resultant complexity was necessary in this system I just simplified to the same basic system found on new cars today.

The POA systems runs the pump continuously, the expansion system cycles the pump based on the heat load.

IMO converting to the expansion system is an upgrade.

Do you really want to learn A/C theory?

 

Shafrs3,

If you had to do it over again would you consider the after market system like Vintage Air or Hot Rod Air?

I'm in a position where I have a 73 that was not an original A/C car but the previous owner added all the components for air. Not a totally perfect install but it was not a complete rigged up set up either. It worked years ago but after the heater core started leaking and the compressor froze, little by little most of the components got removed instead of fixed or replaced. I just bought a bunch of old OEM parts to try and rebuild the system again starting with the A/C inside heater box and all the correct duct work. But after reading up on all of the under the hood parts which most are still there, I understand I will likely need to replace everything under the hood to get my A/C working again. This adds up to near or exceeds the cost of the after market systems.

After reading more details about systems like Vintage Air, I understand everything gets ripped out and you start for scratch. Before I though the original duct work was still used.

For now I put this on hold and need to determine do I cut my losses and go with after market or do as you've done and use the OEM duct work for my year with upgraded under the hood components.

Do you have any pics of your set up?

Thanks

 

Thanks for the info. I understand the basic A/C theory, I'm just iffy about which parts work together. Besides the evaporator, what parts would be needed to convert to the 77L-82 setup?

 

77L-82 you will need

1 R-4 compressor and brackets
2 hard line from the evap. to condenser
3 main hose set off the compressor
4 New dryer/reciever

 

Ecklers carries a "VIR eliminator kit" which contains all of the parts needed to do the conversion (oriface tube, receiver.dryer and pressure switch to cycle the ac compressor.

I spliced in a manual water shutoff valve in the hose supplying the heater core. The heater never sees hot water during warm weather.

 

im not sure about question 2 myself.

 

Yes I would because:

1) I understand some of these kits locate the evap inside the cabin and due away with the evap box in the engine bay, obviously a good thing.

2) They replace the dampener vacuum controls with modern methods.

You might post a new thread here asking for anyones experiences with these products, I'd like to hear them myself.

I have a pic of the general engine bay, not much to see or different except the Sanden compressor. My system is OOC due to a slow leak, another project scheduled for this winter.

 

You'd need the receiver/dryer also, I'm not sure if your system would require any hose changes, mine did and NAPA was able to help me out there. You can use your existing compressor.

 

I also need some info on this,I have 73 that has the GM serpentine pulleys and I'm going to use the r4 compress and was considering changing out the evap. for the 2 line off a later 77-79,or buying a aftermarket assy.and using the r4 comp.
Batman didn't you switch to the serpentine belt?


Could I just swap in a 77-79 2 line evap., and drier and lines and call it good or is there more too it!

 

I'm going serpentine, so the existing R4 is going to be changed out for a serpentine R4. What switches and the like do I need?

It would be nice if someone would create an electrical control kit to get rid of the C3s vacuum controls...

 

Depends on what you want to controll, I have a set of electrically actuated vacuum controll solenoids to run the various dash pots in my HVAC system, and a custom controll panel...it's the blue **** that selects between a/c, heat, def-heat....another switch to the left controlls compressor on or off, heat controll is to the right, main power is upper left, and 2 speed fan is upper right....pick your 2nd gear, you certainly don't need 4 of them....I run a C4 blower, and my install there is 12 years old, so not too clean anymore....
the vacuum/electric solenoids are from junkyard GM cars of newer types........

none of mine is a plug and play, you gotta solder wires right, and know WTF you doing...no way around THAT fact....

 

I am now rebuilding my original '71 A/C and so far I have around $700 of parts and I am still not done yet! besides I am doing all the work myself. I expect to end up spending close to a $1000 before having a cold air in the cabin. If the time will go back I would get a Vintage Air with no second thought.

 

Just that one low pressure switch, available at Autozone. You use the existing compressor power feed, run it through the switch and you're good to go electrically.

You'll also need the orifice tube, various O-rings, the appropriate oil, can't remember the misc little parts, not that there would be many, but nothing out of the ordinary.

Since you're replacing virtually everything you might consider a horizontal flow condenser, it'd save you from flushing your old one, and they're suppose to be more efficient. PM Zwede for a source on these, I used it and got one for around $115.

Also, it'd be a great time to do that C4 blower fan upgrade.

 

Yes, I'm just not sure about the specific hose ends.

 

C4 blower upgrade is definitely in the works. I might actually work on it tonight - I have a complete evaporator/blower case salvaged from Durango's A/C delete. My evaporator case has a big-azzed hole in it, anyway...

I have a parallel-flow condensor from a Dodge van in my garage, I'm just trying to figure out a good way to route the lines.

 

I'll throw my $.02 into this topic. I've converted my 74 from a VIR system to a cycling with the eliminator kit. I'm not real thrilled with the outcome and might go back to the VIR. Here's the reason. The A6 compressor used on my 74 requires quite a bit of HP and Torque to get spinning. On a VIR system this isn't a problem because once you get it going it runs all the time. Using a cycling system the compressor cycles on and off depending on the demands of the system. I find it annoying to feel that big compressor cycling on and off pulling the engine power down as it does so, not to mention the associated belt slippage which sometimes causes a shriek when the compressor kicks on. If you notice, most new cars and aftermarket AC companies use the smaller Sanden type compressors which do not require very much HP or Torque to get going so you feel almost no change in engine rpm when they kick on or off. If you want to feel what a cycling system feels like just drive your car and switch the AC on and off about twice a minute. When you switch it on you'll drop 3 to 5 mph if you don't compensate with the gas pedal. As far as cooling goes the cycling system doesn't seem to cool any better than the VIR. In all honesty I think I should have gone aftermarket given the amount of time, effort, and money I've put into my system. YMMV.

 

I have had minimal cycling w/ both the R4 & ND compressors (late 77 w/ orifice tube A/C system). Maybe a different pressure switch would help some. In fact the pressure switch can be jumped w/ no ill effects w/ the later orifice tube systems as long as no leaks. (Probably one should be sure system is not overcharged to try this.)

I replaced the R4 with a ND 6P (similiar to Sanden 508) which uses less HP & works great. Compressor, custom brackets & hoses to stock original A/C system w/ R12.
I modified Max. A/C High only to have adj. speeds like Normal A/C in the 70s. Also changed Low to Off.

 

+1

My centiments exactly.

Old systems are not designed to cycle and you will definetly lose efficiency and cooling. And yes, it would be very annoying for that big A6 to be kickin on and off.

Either put it back to its factory design or go aftermarket. If you go aftermarket, you won't have the heating of the AC system that plagues factory C3 systems. On the aftermarket kits, the evaporators are in the cabin, not the engine compartment and that helps them immensely.