VetteMed

Thanks for the thoughts... it's definitely a head-scratcher . Here's the thing -- I removed the blower module, and put the vent thermometer in the hole, and still could not get it to indicate less than 58-59 degrees.

I'm not sure that the IR readings on the core are accurate -- I held the trigger depressed and the temp kept dropping, down to below zero -- and I think that's impossible given the properties of R-12, as I understand it. This was with the blower motor connected, so I don't know if airflow can "confuse" an IR thermometer...

VetteMed

Finally had somewhat of a breakthrough today. I took the ZR-1 on a drive for a few hours, in the process of buying a new truck (2500HD Duramax -- wooo!), and I figured I'd BS with the dealership owner to see if he had any ideas... turns out he's got an 86 C4 and a few other toys, and he referred me to a shop in the area. One of the techs there came out to look at the car, eyeballed everything, felt the refrigeration lines, then got in the car for a few minutes. He figured out that the recirc door was not closing under any circumstances. I got home and dropped the hush panel and found the vacuum line leading to the recirc door was malpositioned on the actuator, and therefore the door was continually allowing fresh hot air into the cabin. I didn't test drive it again yet, but I was able to get 55 degree air from the vents, in the driveway, so I'm hopeful that perhaps 50 may be attainable at cruise. More to come...

VetteMed

Took it for a drive today, couldn't find my vent thermometer, but it was a very comfortable drive, even with ambient temps in the high 80s. I don't think it's really working at 100%, but it might be enough to do the job.

Tom400CFI

Weird. On all of MY cars, I get colder vent temps with the thing set in "vent/AC" than in recirc. I think that you SHOULD see the temps you think you should from the vents, even w/o the recirc door functioning. JMO.

This has been an incredible thread. One of the best I've ever read on the forums. Thanks for sticking with it and updating as well!

VetteMed

I'm glad that others can learn at my expense ... I agree with you, there's no reason why this thing shouldn't be blowing ice cubes out the vents, but I've got to take this as a small victory until I determine what else may be wrong. I would expect recirc to cause colder vent temps because it's using already-cooled air across the evap core, rather than hot outside air across the core. Not sure why your system seems to work differently

myk7

Perhaps with everything in the system being changed, the 2.25 pounds of freon spec is no longer valid... may be 2 or 3 ounces over or under? It's been a while since I worked on r12, but I seem to remember that I went for 32 pounds on the low side on a nice warm day at 1500 rpm.

Just throwing things out there..

VetteMed

I had considered that as well - but I don't know how I'd go about finding out if it's under or over-charged relative to the spec.

myk7

I'd try that again. Remove some freon to get the low side down to 32 and see if that makes any improvement on vent temp. You can always add more if it gets worse.

SunCr

You need it on recirc for the best vent temp Most coils can drop the inlet 20 to 25 degrees - a 40 to 50 degree drop is unheard of - if you start with 80, you get 60; once at 60, 40, etc, etc. Make sure everything in the box is sealed. Evaporator and heater core replacements along with aging ductwork (which is sealed with foam), makes for air leaks. If the car has been wrecked, these items (especially the outside air inlet) are often neglected.

VetteMed

I guess I can try that again once I find my vent thermometer. thanks for the input again!

VetteMed

Well, the car has never been wrecked, but I did replace the heater core and as such the possibility of leaks at the duct connections is a possibility. Now that I've got the hush panel removed I'm going to make more of an effort to rule this out. Thanks for the input!

VetteMed

One other thing:

As of July 6, 2011, the manufacturer and the vendor have become difficult to deal with in an effort to get a refund or replacement for an evaporator that was built defectively. Vista-Pro is the manufacturer, and Air-Parts (in Arlington, TX) is the vendor, I would caution everyone to avoid buying parts from these companies as obviously quality control is not a priority.

Tom400CFI

Neither is customer service, apparently.

Thanks for that update too.

VetteMed

Update: AC has been working adequately for several weeks now, however, I left the car sitting for about 2 weeks, drove it down the road last night, the AC "seemed" cool in the brief trip, parked it, drove it to work this morning, and the compressor won't turn on. Jump the low pressure switch, compressor runs. Checked the pressure, none -- system is "empty". SO it went from having enough refrigerant to at least blow cool last night, to empty this morning. I did notice after the brief trip, when I parked it, I heard what sounded like sizzling, I figured it was condensate dripping on to the headers somehow, so I didn't give it a second thought.

I can see oil all along the seam at the front edge of the evaporator housing (blower box), and on the frame rail below the housing. No other signs of oil near the other fittings in the system. I'm guessing that either there's either a blown-out o-ring in the high side right above the orifice tube (due to improper o-ring selection or installation), or there's been a component failure due to a design or manufacturing flaw. I'm hoping it's just my screw-up here, and I don't have to fight with yet another evaporator manufacturer.

I suppose one other possibility could be that the low pressure switch leaked, but I think it'd have to be a pretty major failure to lose that much refrigerant overnight. I don't see any sign of such failure on the switch.

-=Jeff=-

I would think a low pressure leak would be longer to deplete the system

My 99 GTP when I owned it had cold AC one night on the way home from work.. next day Nothing. turns out the condenser was leaking and it all leaked out. replaced the condenser and the system worked once charged

I am close on mine as well, I would like to find a Micron gauge but the system has been holding vacuum since I ran the pump on Sunday..

VetteMed

Yeah, this seems like a catastrophic failure to cause overnight loss of all refrigerant

I'm going to pull a vacuum later tonight to see if I can detect an audible leak, plus I'll pull out the blacklight to look for any dye leakage.

VetteMed

I may have found the source of my leak -- the o-ring at the base of the low-pressure cutoff switch may have been sealing poorly. I pulled a vacuum on the system, it was leaking 1 inHg about every 10 seconds, until I removed the cutoff switch. I swapped in a different switch, same problem. With the switch removed altogether, no drop in vacuum. New fatter o-ring, reinstall switch, it's now holding vacuum for a few hours so far....

VetteMed

I realize this thread is almost a year old, but I wanted to post a conclusion. The replacement o-ring sealed the pressure switch properly, and the system has been working well ever since. It seems to me that the biggest limiting factor with the system now, is the sun load through the windshield -- and that's even with the solar ZR-1 windshield! Driving on cloudy days, or on shady roads, is immensely more comfortable than in direct sun. When the sun load is low, the cabin cools off very nicely.

At some point, when I have some free cash (hah), I'm going to replace the stock windshield (which is now very pitted and in poor overall shape at almost 200K miles), replace with a plain C4 windshield, and have a tint shop apply AirBlue clear ceramic tint to it. Supposed to be very good for heat rejection.

dawghauler

just for gp air outlet temps in the non recirc mode (ie fresh air ) will generally run about 20 degrees lower than amibent temps. low pressure side pressures are related to the amount of heat removed from the air flow for which its cooling. high side pressure is the combination of fore mentioned heat plus the heat of compression. therefore hi amibent/ hi humidity will seriously increase all readings. Got to commend you on your dedication to solve your nightmare as most people view refrideration as Pure Magic