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You need to have someone test the pressures and put in some dye.
Did you replace your accumulator (good source of leaks)?
Did you replace the orifice tube? If not maybe it has debris clogging it.
Simply a few more things to check.
I had mine at the A/C shop five times before I got it right. Leaks and more leaks. So I feel your pain.
I went to Autozone today and rented a set of AC manifold gauges to check the pressures.
- Before starting engine the static pressures on both the Low and High sides were 100psi and checking a second time later after the system was off for 5 minutes 115psi on both sides
- Initial startup of system Low 60psi and High 290psi
- After 5 minutes of running the system at idle Low side 60psi and High side 340psi
- During ~5 minutes of 2000 RPM the Low side read 50psi and High side 350psi
The compressor did not cycle during the testing and the pressures stayed at the readings above, the Low side never dropped and the High side stayed consistent.
I did some research and it looks like these pressures are normal for R134a?
Am I correct in assuming these PSI readings are normal?
Can anyone make heads or tails out of these reading or why the compressor does not cycle or pressures do not come down?
Still stumped as to why the AC temperatures are not as cool as expected inside the cabin? Could the radiator seals not being installed cause this? Does this sound like the evaporator could be clogged?
I am thinking maybe my next step should be taking the car to an AC repair shop and have the system evacuated and recharged with proper levels of oil and Freon?
One more thing to check. Is the pressure cycling switch for R134? The switch is different for R12 and R134. Just another thing to check.
I don't know about the pressures as I let my A/C man handle that. The pressures on the high side seem high though.
Taking it to a reputable shop is the best option now imo.
Edit - You can connect the the two prongs on the pressure cycling switch together and see if it comes on or not. Don't leave it that way though. Just use it to test things.
Last edited by Street Rat; 08-24-2016 at 07:58 AM.
Reason: add info
One more thing to check. Is the pressure cycling switch for R134? The switch is different for R12 and R134. Just another thing to check.
I don't know about the pressures as I let my A/C man handle that. The pressures on the high side seem high though.
Taking it to a reputable shop is the best option now imo.
Edit - You can connect the the two prongs on the pressure cycling switch together and see if it comes on or not. Don't leave it that way though. Just use it to test things.
Well I took the car in and had the system evacuated and recharged. The AC shop said the compressor, AC Hose, accumulator, orifice, o-rings and possibly the condenser needs to be replaced. The system will not bring the pressures down on either the high or low sides, nor does the compressor cycle. When checking the system they found the oil/system had a red substance in it. The only other time the technician said he saw that was when a leak sealer was injected in the system. Now I know what the engine builder did to stop the seal leak in the AC hose.
Now, they are saying they would also recommend replacing the condenser as well since they don't know how contaminated the system is with the unknown red substance. Then vacuum, pressurize with Freon, check for leaks and test the system. This may not take care of it all according to their technician and the evaporator may also need to be replaced due to unknown contamination. Well that would mean the whole system would be replaced at that point.
Can the evaporator and condenser be flushed? Is it something I can do at home and using what cleaner?
One good thing the owner said if I wanted to buy my own parts, do the work at home and then bring the car back to have the system vacuumed and recharged, that he would have no problem with me buying all the parts and installing. That would save a considerable amount of money on labor and I have no problem doing the work myself.
The question I have is, how do I know if the condenser and evaporator need to be replaced if they are not currently leaking?
Would it be due to the leak sealant?
Anyone have recommendations?
How about where and what are the best parts to purchase. I see a lot either NEW, Re-manufactured or Rebuilt. AC Delco, Four Seasons, and others, but AC Delco and Four Seasons seem to be the most available.
Any recommendations on where to purchase all the parts? I have been looking at Zip, Ecklers, Corvette America, Rock Auto, locally etc.
You can buy flush kits from four seasons etc. But if you are bucks up you might take this opportunity to upgrade to a new system. The evaporator core might be a little tough to get out with the engine in the car but I see people here that do it all the time.
I called Classic Auto Air and purchased a kit for my car. It comes with a Sanden compressor which is more efficient than the factory compressor. All brackets and hoses are included. What is not included is the parallel flow condenser, the evaporator core, and accumulator. Reuse your metal line from the condenser to the evaporator core. You have two hose ends that would need to be crimped after the hose length is determined.
I did the upgrades to mine and it will freeze you out on a hot day. My car is black and has glass T-tops as well.
I talked to a man named Ron at CAA 866-352-4678. You won't see your year model listed so call them.
You can buy flush kits from four seasons etc. But if you are bucks up you might take this opportunity to upgrade to a new system. The evaporator core might be a little tough to get out with the engine in the car but I see people here that do it all the time.
I called Classic Auto Air and purchased a kit for my car. It comes with a Sanden compressor which is more efficient than the factory compressor. All brackets and hoses are included. What is not included is the parallel flow condenser, the evaporator core, and accumulator. Reuse your metal line from the condenser to the evaporator core. You have two hose ends that would need to be crimped after the hose length is determined.
I did the upgrades to mine and it will freeze you out on a hot day. My car is black and has glass T-tops as well.
I talked to a man named Ron at CAA 866-352-4678. You won't see your year model listed so call them.
I was just going through the parts list, the cost as well as where I can purchase all the parts and then getting ready to add up what it would cost me to replace all the current system parts.
The shop did say they were able to bring down the low side a little bit after flushing, replacing the Orifice Tube and re-charge, but high side pressure is still too high and the system is not cooling. They believe it is clogged up in either the condenser or evaporator and said I could replace all the parts myself and try flushing out the condenser and evaporator. But they are also recommending changing the evaporator to be safe. Then bring it back for vacuum and re-charge.
I tried to find a place online for Classic Air, but as you said they do not list a 1981 Vette. I will give them a call.
I am going back to pick up the car this afternoon. The shop I found was very open to working with me as well as lending tools if I needed
A/C systems are not as complicated as folks make it out to be. I am using my original compressor with original hoses and condenser converted to 134a.
The biggest issue in the conversion is getting all the mineral oil out since it is not compatible with PAG oil used in 134a. It sounds to me that the folks who did your conversion did not do this if red dye was found in the system.
As an alternative Ester oil can be use in conversion to 134a as it is compatible with mineral oil used in R12 systems.
The freon itself does not care other than R12 is not too effeceint at carrying PAG oil. Ester oil however is good for either system and is what I use in my system.
You could flush your system out. This would entail disconnecting the condensor and the evaporator from the system to effectively flush them individually using a flush fluid followed by compressed air. As a follow up denatured alcohol can be used to finish the flush as it readily evaporates and will carry much of the flush with it when you use it as a follow up flush. Just remember to add in the appropriate amount of oil once a system has been flushed. I put 1/2 in the compressor and the other 1/2 in the accumulator/ filter-dryer.
Here are some flushes for example. https://www.amazon.com/FJC-2032-Flus...c+system+flush
A/C issues will rise up again and again over time, not neccesarily on the same vehicle but over time on your vehicles. I found the best way to handle it is to do it yourself, or at the very least diagnose it yourself.
You can vacuum down and charge your own system saving you many $$ and much time vs taking it to a shop.
You can learn a lot from going to an a/c forum. Those guys, some professionals, can teach you plenty even if you only read posts.
You may need a new orfice tube. If I was in there I would replace it as well as the filter-dryer/accumulator.
The pressures you posted before were really high on the low side. 55 psi is pretty much the max for any 134a system regardless of the outside temp.
Here is a chart that includes duct temp and humidity in the mix. Some charts out there ramp up the pressure too fast which results in overcharging your system. Use the lowest pressures that provide the best duct temps. More freon does not make it cooler after it's full.
One more thing I forgot to add is that vacuuming all of the air out is very very important. This step not only removes air but moisture as well. With the pressure reduced the moisture will boil off anf be removed from the system. Leaving the hoses connected with the vacuum pump off and guage valves closed, is also an effective way to check for leaks. The system should hold the vacuum pretty much indefinitely if left there.
Excellent post!
I wish I would have purchased the tools now. Mine was in and out of the shop five times before we finally got all of the leaks fixed. I could have done it myself.
Last edited by Street Rat; 08-30-2016 at 01:27 PM.
I picked up the car today and they vacuumed the system down until I can order and replace the parts. I am looking for the parts at various Vette vendors, Rock Auto and locally. My plan is to remove everything and flush out the evaporator, install all the new parts and take it back for vacuum and recharge. They will also check for leaks and correct any if found. The AC shop (Viking Electric and AC) is very accommodating installed a new Orifice tube at no charge during troubleshooting and even gave me a can of flush to use. They also recommended replacing the condenser with a Parallel Flow condenser to help the temperatures and pressures to come down as Street Rat also recommended. I called Classic Auto Air and spoke to Ron, they have a custom direct fit Parallel Flow condenser for the 81. Thanks for the recommendation Street Rat, they mentioned the PF condenser will help cool things down.
Hopefully I don't need to go back and forth too many times and not many leaks show up or they are able to find them at the time of vacuum and recharge.
I thought about buying the tools mentioned and was on my way to pick up at HF last week until I found this AC shop that was willing and open to work with me. I also found I can rent the gauges, AC Flush Kit, and other tools from AutoZone down the street for free, just leave a refundable deposit.
Just an update. I had time this past weekend to take out all of the A/C system components except for the evaporator. I'll be flushing out the evaporator this week before installing the new components. I have picked up and ordered the rest of the new replacements parts for the system. The new Parallel Flow condenser arrived, it is much lighter than the old tube style and looks very nice. Hoping it makes the difference in the cooling as much as everyone recommended from the A/C shops, others that have completed the retrofits and classic A/C shops, along with keeping the AUX fan running when the A/C is turned on.
I also had a chance to test wire the relay to allow the factory AUX fan to come on when selecting Normal or MAX A/C. Works great, just need to permanently mount the relay on the engine bay firewall and solder a couple wires!
I did find some interesting information online as well as discussing with a local mechanic that suggested the installation of a Flyback Diode between pins 85 and 86 to prevent the switching device, in this case the A/C Low Pressure switch from burning out it's contacts prematurely due to each time the fan is shut down an arc is created. Not sure of anyone else has done the same for fans, lights etc.?
Well I got all the new A/C parts installed and the car taken back to the A/C shop for vacuum and recharge. The shop called and everything is working great with 45 degrees being produced in the evaporator box. But the problem they are seeing after the car warms up the inside vent air temperature climbs up to 68 degrees and stays there while the evap box stays at 45 degrees. The tech can feel one heater hose to the heater core lukewarm where the vacuum valve is inline and the other hose hot. That sounds normal, but the air is getting hot between the evap plenum and the inside vents. The tech said he also checked the evaporator plenum for debris and it is clean as a whistle. He also said the blower and valve doors are operating as normal. The blower itself is the strongest he has seen on a corvette. He has an 82 vette in the shop also and it does not blow as well as my 81
From reading on the forum other members had similar issues and found if they shut off both heater hoses with ball valves that solved the issue? Does that sound what is possibly happening?
There is a vacuum switch behind the glove box. A cable under the right console cover can be adjusted to close the heater damper all the way. It sounds like the cable is not closing the heater damper.
OR
The vacuum operated switch is not working correctly. Possibly not shutting off your hot water valve in the engine compartment when the lever is in the cold position.
There is a vacuum switch behind the glove box. A cable under the right console cover can be adjusted to close the heater damper all the way. It sounds like the cable is not closing the heater damper.
OR
The vacuum operated switch is not working correctly. Possibly not shutting off your hot water valve in the engine compartment when the lever is in the cold position.
Thanks Street Rat.
I played with that vacuum switch and cable a few weeks ago and thought I had it set up for factory settings and it was working correctly while testing with my hand vacuum pump. Maybe it is not working 100%.
Well the Tech just called back and said the A/C is still cooling great down to 40-45 degrees in the plenum, but he did find the heater core is getting hot causing heat transfer inside the vents. So looks like I need to replace the water shut off valve or get a couple of manual ball valves.
08-23-2016, 10:20 PM
Low and High side Pressures
