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Hi, I had the compressor replaced on my '85 C4 with glass top today. The outside temperature here in Kansas was about 95 and I am sure the humidity was pretty high. The output temperature coming home was about 50 degrees. It was cool in the car but it wasn't running me out. That is a drop of 30 to 40 degrees from outside temperature so I am probably okay but thought I would check in with others. The shop owner also said he didn't think my fan output was up to par so I will probably change that out tomorrow.
Did you happen to ask the shop owner what the gauge reading were at the time of re-charge/Service?
For quick reference (Rule of Thumb) if low pressure side is averaging 30 PSI--out let temp should be very close to 30 degrees F (32-35 or so)--measuring generally on left center vent (closest to evap core)
Many things can affect this reading, blend door not closing properly, blend door mis-adjusted, browden cable mis-adjusted, blocked evaporator core, list is long.............................--has dash been apart?
Next, lower blower speed/air flow will give a lower temp from the vents--think about moving your hand quickly over a block of ice or slowly moving your your hand over the ice--hand feels colder if held over ice longer---(slower)
Faster air speed/volume will cool quicker as warm air is moving out, which "feels better"--yet, lowest outlet temps will result by lowest fan speed (less volume)
If the compressor is cycling off the pressure switch my need to be replaced or adjusted if it is the adjustable type. The fan output was never great on the early c4's due mainly to the small thick evaporator coil. Replacing the blower motor didn't help me. My evaporator was very dirty and partially clogged with leaves and pieces of the original foam filter which disintegrated from age. You can't really clean them good in place so I replaced mine. Unless you want to spend a lot of money, 50 degrees is not bad.
If the compressor is cycling off the pressure switch my need to be replaced or adjusted if it is the adjustable type. The fan output was never great on the early c4's due mainly to the small thick evaporator coil. Replacing the blower motor didn't help me. My evaporator was very dirty and partially clogged with leaves and pieces of the original foam filter which disintegrated from age. You can't really clean them good in place so I replaced mine. Unless you want to spend a lot of money, 50 degrees is not bad.
Beat me to it. This was my exact thought. Faulty pressure switches will cause it to cycle on and off, much of the time without you realizing it. I replaced mine on my Tahoe last summer and now my AC freezes me out in Arizona when it's well over 100 degrees outside.
Was it changed over to 134a? What happened to old compressor? Were orfice tube and accumulator replaced? Manual or automatic ac? Is condenser clear? c4s can act like a vacuum cleaner.
Thanks for all the responses. I am assuming the pressure switch is the port on the high pressure line about even with the middle of the motor. If that is the pressure switch I may see the problem. That switch is unplugged and the connector looks like it has been jumped together. I will do some reading. Now for the newest problem. Nothing is easy. I pulled the blower motor to replace it and the high blower relay wiring is toast. The relay has obviously gotten hot but the female 5 terminal connector has really gotten hot. I haven't check it with a ohm meter but I think it needs replaced. Any good source for the connector that I can then splice it. Nothing is ever easy.
Thanks for all the responses. I am assuming the pressure switch is the port on the high pressure line about even with the middle of the motor. If that is the pressure switch I may see the problem. That switch is unplugged and the connector looks like it has been jumped together. I will do some reading. Now for the newest problem. Nothing is easy. I pulled the blower motor to replace it and the high blower relay wiring is toast. The relay has obviously gotten hot but the female 5 terminal connector has really gotten hot. I haven't check it with a ohm meter but I think it needs replaced. Any good source for the connector that I can then splice it. Nothing is ever easy.
I believe that's a very unusual connector if still original. The connector attaches to the blower housing and the relay plugs in? GM/Packard original I believe would have been #12010179. There's very likely connectors that you could use but they would have no retention options to the blower housing. A GM# 12102684/ACD PT351 (obsolete also) or equivalent would do the correct terminal. The terminals are very straight forward Packard 56 Female and should be a local buy.
4 Seasons shows a GM style connector but you are correct it doesn't have the mounting points. I may have to do without the mounting points. It really can't go anywhere down there. I am worried as one review showed the working a bite lighter gauge. As bad as the connector itself was burned/melted I don't know if that might be a good thing. The other issue is the high pressure switch. I am still working on that connector.
4 Seasons shows a GM style connector but you are correct it doesn't have the mounting points. I may have to do without the mounting points. It really can't go anywhere down there. I am worried as one review showed the working a bite lighter gauge. As bad as the connector itself was burned/melted I don't know if that might be a good thing. The other issue is the high pressure switch. I am still working on that connector.
What wire colors and which circuit numbers for the switch connector? Do you have the FSM?
** A GM# 12085503/ACD PT124 (still available) or equivalent should do the switch you mention. I assume you're talking about the gray (likely) on the AC line? The switch is GM# 14078970 or an equivalent.
*** 7/06 This is of course incorrect information for the switch and connector you need.
I usually switch from the transparent top to the painted top when the temperature starts getting higher . My first Corvette was a 96 base LT1 coupe . I thought the system on that car worked pretty well . It came with just the painted top . I bought a transparent top to have an option . Still AC performance was better with the painted top .
My other two Corvettes have been 91 ZR1'S. The LT5 produces higher temperatures under the hood. They went with a compressor that was 10% smaller to get it to fit under the LT5'S plenum . They added the solar coated windshield to help the AC system performance. If you go to the ZR1 specialist website you will see a section on improving AC performance under the heading of presentations.
What Marc Haibeck found was he could increase the blower motor speed 23 % by making some modifications to the wiring and replacing the cars 124 Amp alternator with a 200 Amp model. It seems by running several wires in parallel to existing wiring can keep the voltage up going to the AC and blower motor . It's a good read . Question is can these mods also improve AC performance on other C4's .
I have found the wiring connector and the relay and have both on order. The switch on the right in the picture is I believe the high pressure cut out. Everything seems to work with the broken switch plugged into the damaged connector. That is the way I found it so I am not sure what happened. If you know for sure that is the right switch let me know and I will get one ordered. The old blower motor seems to run just fine so no sure if I should replace as a preventative maintenance or leave alone. Thanks Bob
I am still chasing my AC woes. I drove the car yesterday and with the temp in the mid 80s outside it was marginally cool inside. I have a couple of problems I am chasing that may be connected. I removed the entire FI system a couple of years ago to replace a broken thermostat housing bolt. I thought I had everything back together right but when I started looking today I have an open port and not sure where it goes. The other issue is I have a broken switch. The lower body of the switch is still connected to the AC system but the upper half is stuck in the somewhat melted electrical connector. Not sure which switch this one is. Manual isn't much help. To add another one it the cruise control isn't working after my top end reassembly. Any ideas?
Well I found part of my problem. Low pressure in the system. I added about a pound of 134 and the compressor clutch is engaged about 50 percent of the time then the pressure drops and it kicks out. I didn't have my high pressure gauge set so I didn't want to add any more. I added some leak detection but a quick review didn't show anything. I ordered what I think it s the one switch that is broken so I will change it out tomorrow and I have a new pressure cycling switch so I will install that. I installed a new compressor last year and accumulator. The technician said he thought the hoses looked good so we didn't opt to replace those. I will see after some updates what is happening. I have also replaced the blower motor and the high fan relay with new wiring connector so that part is good and I can hear the various fan speeds so that is good.
AC temp output
