More A/C questions
 

Halfway into getting the original air back in service on my 64 vert but I had a few more questions.

1) dismantled the STV valve and found it to be quite nasty inside. I am not sure the piston assembly can be reused. I am now considering using the kit which guts the valve and cycles the compressor. Is there any downside to this other than appearance? With this conversion, can I still use either refrigerant?

2) I plan to use a pro6ten compressor. Am I correct in assuming it bolts in to the original A6 location without any changes? I finally have all the correct brackets in place. Also, will this compressor work well being cycled by the switch after converting the STV valve? Will the compressor work with either refrigerant?

3) when I installed the condenser, I went with a modern parallel design rather than the original serpentine design. Will this condenser work well without a fan? I hate the idea of using electric fans. I know it is preferred for r134, but will the parallel unit work well with r12?

4) Lastly, I am at a loss for refrigerant. I can get r12 easy enough. Any cooling advantage? I simply want the coldest most reliable cold air I can get.

I know there's a lot there so thanks for your input in helping me finish this off.

I've been using r134 for years in my 64 with a completely stock setup. Works fine, cools fine.

One possible downside to using a pressure switch instead of the STV is that the A6 compressor clutch may not have been designed for repeated cycling. I don't have any experience with pro6tem compressors. They should be able to tell you if the clutch is designed for cycling. There is no reason a parallel coil wouldn't work with a stock fan.

I've converted a few late 80s to early 90s R12 cars to R134a. The AC in all of them worked ok, but there was a noticeable drop in cooling performance, especially at engine idle. If you have easy access to R12 why not continue to use it. If you decide to convert to R134a, be sure to use polyester compressor oil and not PAG oil unless you are able to completely clean out the old R12 mineral oil from the entire AC system. My understanding is that PAG oil can react with mineral oil to form a really nasty, hard to clean sludge.

When I order my compressor, I'll ask their tech people if it is designed for cycling.

Many of the underhood pieces were missing when I bought the car. The evaporator was there but without hoses, it was open for years. One of my next steps is to spend some time flushing it out. The other components will all be new.

No problem with the older style compressor cycling. The magnetic clutch is on or off, and does not really slip. If anything, less wear on the compressor if it cycles. You WILL need a condenser fan to come on when the compressor engages to keep pressures from skyrocketing. Be it electric or a good HD fan clutch, you can not run without a fan.

Just ordered the STV elimination kit, pro6ten compressor and a new expansion valve. Spoke with the tech as well.

Just came across something else though. In cleaning all the little pieces, it occurs to me that I should replace both of the valve stems in the low and high pressure ports. I'd hate to find out later that they don't seal well anymore. They seem a lot like the ones from car tire valve stems and I see various sets on eBay. How can I be sure I'm using the right stuff? Any suggestions here?

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Before you spend the money for a Pro6Ten ,look at Four Seasons pt.# 58096. When I bought one several years ago it was half the cost of a Pro6ten. It was a new offering at the time and I compared it to the much advertised Pro6ten and the Four seasons unit is essentially the same thing. Direct bolt on replacement for the A6, except it wasn't painted black, everything I saw said the 58096 had the same internals including teflon coated pistons.
I've had it on my big block 390hp for about 5 years, using R 12. My system is original [52yrs old] except for the expansion valve and drier. Draws much less HP. my motor has it's stock 5 blade clutch fan , never overheats and the air temp at the center vent is 38 deg.
Don't know what the Pro6ten sells for now, but the 58096 sells for around $240, I paid $168 for mine and painted it black, it ships oiled for 134r but is easy to change

Just Google AC SCHRADER VALVES. NAPA should have them as well as most auto parts stores. Here is a link to ACDELCO ones, although most purchased from NAPA etc should cost a lot less.


Some have rubber o-rings for sealing, so HNBR is the best for both refrigerants. Teflon will also be good for both.

Your home AC guy probably has a jar full in his truck.........you can also ask him.

Larry

I have the elimination kit on my 62 Bonneville STV system substantially the same as yours, running R134 & the A6. I jumped out the thermostat because I found the cycling bandwidth to be too wide, resulting in a clammy car. This result is precisely what the STV was designed to avoid with a constantly engaged compressor. The kit guts the valve so that the system, already with serious capacity runs wide open. So I cycle the compressor myself to keep it from freezing. As much as I need the A/C it works for me.

I have the same setup on my 63 Impala only I skipped the thermostat and wiring. I run R12 and it cools extremely well. The rinky dink convertible weatherproofing puts enough of a load on the system that I don't often have to use "manual defrost mode."

Whatever you do, remember that this kit guts the valve and runs the system wide open when it runs. GM systems were never meant for that so keep in mind that there is a risk of slugging (hydro locking) the compressor if the evaporator is allowed to turn to a block of ice.

Otherwise by all means carry on.

Dan

Thanks guys. I think I'm stuck using the bypass. The piston assembly inside the STV valve isn't looking so good and I doubt I'd ever find another. I can probably live with a wider temp band of cycling. Better that than freezing the system up running wide open. There could be times in the future when my wife takes it out so I need it to be reliable and user friendly.

I'll still have the old STV parts so if I came across a new piston assembly I suppose I could convert it back. Assuming the little vacuum switch at the bottom still works.

I had one STV restored and its piston hung up after a while anyway. The STV was a flawed design, it didn't last but from 62 to 65 or thereabouts, replaced by the pilot orifice absolute (POA) and was a big improvement.

Make sure that remote bulb on the T-stat gets a good solid contact with the evap line to get the best cycling action.

Dan

The A6 is a strong compressor and the clutch was not meant to be cycled.
The clutch is metal to metal and will be your problem as the pulley has a insert. The shaft is 1/2" at the clutch and when the magnet pulls the clutch hub to the pulley at high engine RPM's it can slide a bit and cause a balance problem. The clutch engaged at high engine speeds will actually throw sparks (metal to metal).
I try to engage my compressors at a low RPM as to save the clutch. I can point out one possible problem one of our members had that we think was caused by cycling. The pulley bearing started seeping oil from the slapping of the hub to pulley.
Good news is that the repo pulleys ARE made differently than the original A6 pulley, it is solid and does not have composition holding the pulley together.
Don't worry about the pulley causing damage to the hood when it de-laminates, the clutch hub clearance will not let the metal ring escape.
Just something to think about.
The newer compressor is most likely built to take cycling. The original looks the best under the hood (if you are going original).

Dom

here is a pic of a pulley that came apart.

Have you contacted David Sokolowski to see if he has a NOS STV. I know he has a lot of hard to find AC items and may possibly have one. 310-329-5334 Pacific Time and his prices are quite reasonable

Well my new pro6ten compressor is already on the way as well as the bypass kit so I'm going to give it a try. According to the tech guy at Old Air products, this compressor has a different clutch design made for cycling and the other internal components are supposed to produce less drag and not affect idle rpm as much.

As cool as it would be to maintain the original look, I'm already running a 1968 327 which is noticeably different than the 1964 design. There are a number of underhood things that make it stand out as non original so might as well add ac compressor to the list.

Got my new schrader valves at the local auto parts place. I'm glad it was that easy. They seem to seal up nicely.

One thing that I am still up in the air about is the electric fan in front of the condenser. The tech guy at Old Air didn't think it was necessary but some of you guys think it is. You guys obviously have a lot more expertise with C2 vettes than the tech guy though. What are the consequences of not using an electric fan? Poor cooling or is my condenser going to rupture from heat and pressure? My car runs nice and cool idling on the hottest day. I've had other cars with electric fans and they tend to create blockage when not spinning. I'd rather not run an electric fan unless it's absolutely necessary. I took your guys advice on sealing the condenser and shroud really well. I'm also running the seven blade fan with a heavier clutch so air flow is quite good.

STV piston/diaphragm is not unobtanium
 

If you ever go back to a stock STV configuration, the original piston & rubber diaphragm assy can be found. They pop up from time to time.
I've bought and sold maybe a dozen over the years. Anything under $80 is a good price. Several auto A/C parts companies offered them back in the day. Obsolete GM parts sellers used to have them regularly.

I'm holding on to the other inner parts and it seems simple enough to put it back if I found the piston assembly. I doubt the vacuum switch at the bottom is still operational but I never checked it out once I realized I'd be converting the valve.

I managed to get a couple bottles of the r12. I suppose I could just stick with that to avoid the idea of electric fans but then I'd have to change out the oil in the new compressor. If I change compressor oil, does it need to be flushed to remove all traces of the other oil? I'm already flushing the evaporator but I don't want to chance hurting the new compressor.

In your New Yorker and Bonneville, are you still using the stock condenser without additional electric fans? In an earlier post, I stated that I'd be fine with r134 but if it meant adding electric fans, I'd prefer r12 since it supposedly operates at lower pressures. All I want is nice cold air in the end without having to jury rig in aftermarket electric fans.