Pete76Shark

I am by no means an expert on this but I have done a fair amount of reading on the subject of A/C and I found that the VIR unit does not have the POA valve adjusted properly for R134a.
It is set for R12 and as such the Evaporator pressure will not be low enough for optimum R134a performance. Now you can put R134a into a stock VIR system and it will work, but not the best.

Since there are a bunch of us with the old VIR system I suggest you read this link and then decide.

I had both R134a and now R12 in my system and I noticed a big difference when I went to R12.

Only reason is the VIR is calibrated for R12 and not R134a.

http://www.autoacforum.com/messagevi...AR_MSGDBTABLE=

PhotoVette1

Yes, I discovered the same thing. I tried R134a, R414b (Hotshot), and R409a. R409a works incrediably well.

Pete76Shark

If you want to purchase R12 legally you must have a 609 certification.

To get one you need to take a 25 question open book test and pay $20.
Here is a conversation about that:
http://www.autoacforum.com/messagevi...AR_MSGDBTABLE=

Now as far as the cost is concerned, well, I cant help you out with that. I purchased (after I got my certificate) a 30lb can of R12 and I have enough for life now.

If you want to charge your A/C system with an alternative refrigerant then you might want to read the following. I am not saying selecting something other then R12 or R134a is a bad thing. You just need to make an informed choice is all.
http://www.autoacforum.com/messagevi...&threadid=9241

Chopper Larry

I've heard you can change the valve, but I doubt it still workds as well...plus the r134 is more corrosive.

Pete76Shark

If you open up the VIR you can change it and adjust it. Nobody seems to know exactly how many turns to adjust the POA valve to make it work well with R134a.

I was looking for a LARS caliber A/C guy that did the research and could report what was needed to be done exactly but never found it.

zwede

I have a 71 with the separate POA valve (not VIR). I adjusted mine 1/4 turn CCW and it dropped my vent temp from 52F to 44F. This is with R134a. Don't know if the VIR POA is the same as mine but maybe a place to start?

Wrencher

I repaired and converted a '73 with a VIR system and the valve we got from Mid-America was set up for R-134A. we got vent temps that varied between 38-42 degrees on a 85 degree day. Worked for me!

Hans

jbs75

It's 1/4 turn ccw also on the VIR; got this about 5 yrs ago, and it worked for me.

Rockn-Roll

I'm not an expert, but I bought a new VIR/POA unit several years ago for my original OEM A/C system and the valve was already adjusted for R-134a and came with the green seals. My vent temps are in the low 40's...I just wish the fan would move more air.

zwede

I recently installed the C4 blower & cage and it moves alot more air. The big pile of leaves I dug out from the front of the evaporator didn't hurt either.

Pete76Shark

I also installed the C4 (I think it was a 1996 Vette) blower motor with the cage. Made a spacer and now she blows real good.

Corvette ED

I installed a new compressor, hose, and vir in my 75 last year and charged it with 134 and it blows 39o on a 85o day.

I didn't adjust anything.

87bob

Have you got any pictures of your C-4 blower and cage conversion?

zwede

I couldn't even see the damn place the blower mounts at, much less photograph it!

It's a simple conversion. You need to make a 1" spacer as the C4 squirrel cage is 1" deeper. I used two 1/2" kitchen cutting boards (polystyrene plastic, $5/ea at bed, bath & beyond). I cut the shape with a jigsaw. Used RTV for sealing. Electrical connectors are the same. There's a vent hose from the blower motor to the evap housing. My old one crumbled when removing so I made a new one out of some common rubber hose. A short piece of 3/8" hose into the blower motor hole. 5/8" over it and to the fitting on the evap housing.

PhotoVette1

I put a C4 fan/motor in mine. What I used for a spacer: I got a 6" PVC slip coupling at Home Depot and cut 1 1/4" length section off, then drilled the holes--it fits perfectly.

Corvette ED

How much difference did it make with the C4 blower motor? Did you use the plug connector from a C4 and just splice it in?

zwede

Well, how do I quantify the change? It went from blowing air to [/B]really[B] blowing air. It blows the same amount of air as your typical new car now. On a 100F day I run the AC on max, blower max for the first 5 minutes. After that I switch it to a lower blower speed and go to AC norm.

The C3 connector fits on the C4 motor. No splicing.

carl a

--------------------here's the spacer i made out of a ''stove pipe cap"" i bought at menards for $4, i traced the outline of the fan on the top of the cap and cut it out with tin snips , it was 2'' wide ,so i cut it down to 1 1/2'' and used a vaccume line slit lengthwise for a gasket ,,,then bought 2'' long mounting screws ,,,painted black and it looks better than the ones the guys on this forum made outta wood--- i couldnt see using wood------

TXredc3

I also bought a 1995 c4 motor and squirrel cage. Made the one inch spacer and sealed well. I can only tell a slight difference in the amount of air that is blowing through the vents. Not sure what to check next. Any ideas?

zwede

The box may be plugged by leafs and debris. You can get most of it by removing the two things that bolt to the side of the evap box (close to the blower motor). The holes let you fish out the junk. I also found debris in the passage between the motor and the box, accessible (barely) after removing the blower.