i have a 75 vette i am in the middle of a frame off
my mechanic told me to try and get a later model evaporater core like a 79 or later he explained theat my year had some inherant problems
can i buy a new system for a 79 to replace mine or are there some i problems i may expect


thanks donnie

 

I have a 75 and it has A/C problems but it's not related to the evaporator, it's the VIR system and the valves inside that stick that cause the evaporator to freeze. There's some guys on there that have no problems with them at all and their system works fine, others like mine do not. In my opinion changing the evaporator will not solve inherent problems these things have. I'd love to get rid of the VIR and change the compressor to a Sanden with modern controls. There's some folks on here who've done that and seem happy with the results.

 

The reason why your mechanic suggested a 79 evaporator is because it does get rid of the vir and switches to a oriface tube. The virs' are better when working, but they are not made any more.

http://www.ackits.com/merchant.mvc?S...t79corvette5-7

If you have the a6 compressor keep it if you like it. It is one of the best ever.

 

That's good information Noonie, thanks for passing it along. I may look into it myself

Bill

 

Noonie, I hope I'm not hyjacking this post but this is related:

I'm interested in hearing about possible VIR problems. When I first got my car the A/C wasen't working so I charged it with R12, worked OK (nice and cold) for a few days then blew a hose. I bought and installed new hoses and while I was at it I thought I may as well replace the VIR. Worked but soon afterward started freezing up the condenser so the A/C guys (who are real old timers and very reputable) told me about the sticking POA valves and offered to swap it for me. They took the one from my old VIR and it does the same thing. So I bought a used VIR and removed both valves to replace them both this time. These used valves are very clean and seem to work fine by hand but I actually don't know if they are good either. I haven't changed them yet, do you think there could be some other cause besides this POA valve sticking, it seems pretty crazy that 2 of them would be bad.
I did have the dash apart to change the heater core last year and the condensor is clean as a whistle, no debris or anything.

Thanks,

Bill

 

If the temp bulb at the end of the Expansion valve capillary tube is not clamped snugly(not too tightly) and then wrapped with the gummy insulator,to insulate it from the outside air temps.The expansion valve will not function correctly.
Here's how it works. Capillary from the Expansion valve senses evap temp. As temp drops oil in capillary contracts and causes valve to close. as temp increases valve will unseat and let refidgerant flow into the evaporator.
If its freezing up the expansion valve is likely the culprit. It would help to know what your High and low side pressures are to accurately diagnose

 

Thanks for the reply. This system doesn't use the temp bulb. I'm only knowledgeable enough on this to be dangerous but I believe this system uses the POA valve to allow enough hot gas to bypass and keep things from freezing up. When it malfunctions or sticks, then the system goes out of control and the evaporator coil ices up.

 

When the POA sticks. it turn the expansion valve into an uncontrolled oriface tube, hence the freezing. Temporarily, it can always help to not use the Max air setting and depending on your comfort level crack the windows a little to introduce warm air into the cabin and try tapping lightly on the POA

 

Hi Noonie,

Thanks for reading the above. Did you happen to see my question to you in the previous post #5 regarding other possible causes??

Bill

 

Hey guys,

I recently got round to finlly fixing my ac in my 77. I charged it up with r 134 a as r 12 is to expensive. it worked okay but never that great, then my hose started leaking so I decided to fix it right.

I went to a place called AutoCool in atlanta, where I live, and they suggested that I convert from the VIR system to a modern style accumulater. I want to say that it was actually designed for a late 77 model, post VIR era. I put in the new accumulator, had to buy a new hose (similar, but it had a slightly different end on one end to mount to the accumulator), installed a thermostat swith into the evaporator coil, and installed a universal oriffice tube.

It all fit in the stock location and I did not have to modify anything to make it fit. It was a little tight and a bit of a pita, but it all turned out well. It now blows 40 degrees, even here in the hot georgia sun when my thermometer that I have in the car reads 110 when I get in, in about five minutes, I have nice cool 40 degree air blowing in my face. I couldn't really be happier.

That said, it all cost me about $350 for parts and I installed it my self, vaccumed out the system and charged it up with one 4oz can of oil and 4 12oz cans of r 134a.

I would recommend calling these guys and talking to them, they are real nice guys and helped me out no problem. Their # is 770-433-2665. I talked to fred, and he knew exactly what I needed to get it working right....

PM me if you need any more info. and I'll do what I can to help out.

Good Luck,

Will

 

It was common for the poas' to stick. You would have to disassemble the complete system, flush etc., new bag, refill r12 expensive etc. You should be able to take the poa to your old timers and they can test them for sticking.

Bottom line, though is that you are really better off to change to a o/t cycling system. Sticking with what you have can cost a fortune over time.

 

I thought that was a separate piece from the evaporator...

 

Thanks for all the good info and the offer!!!

 

You're welcome....And like I said, let me know if you need any more info...

Will ....

 

OK, thanks

 

Yes, late 77 uses the orifice tube A/C system & same evaporator used late 77 through 79.

Late 77 w/ the orifice tube A/C system.

 

I have a complete AC unit, except the hoses, from a 69. I never had it hooked up, don't know if it works...its unhooked from the motor and frame, can it still work if the compresser was spun, say like on a drill motor? or is there more to it??

 

It takes a bit more than a drill can do to spin it up and make anything happen. The spinning part is the clutch to a compressor that requires (I think) about 10hp to run at speed. Put a belt on it and turn it on, see what happens. Worse thing can be is if the compressor is locked up

 

You'll also have to apply 12v to the solinoid to lock up the clutch. Then hang on to the drill baby!