Man, It's hot.
Thread Starter
Racer
Joined: Nov 2011
Posts: 274
Likes: 12
From: Louisburg NC
AC pressures
Can anyone tell me what the AC system pressures should be in my '94?
Current readings are 160/30. Ambient air temp is 84.
Current readings are 160/30. Ambient air temp is 84.
Last edited by oilyfishhead; Jun 30, 2012 at 09:29 AM.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
I'd imagine it's low and pulling down at speed and cycling off or maybe the Low Pressure Switch needs to be readjusted for R134 - but get operating pressures with the engine at 1500 rpms, Main Fan running, system set to MAX. If it cycles off, note the low side when it does. Repost.
Thread Starter
Racer
Joined: Nov 2011
Posts: 274
Likes: 12
From: Louisburg NC
I'd imagine it's low and pulling down at speed and cycling off or maybe the Low Pressure Switch needs to be readjusted for R134 - but get operating pressures with the engine at 1500 rpms, Main Fan running, system set to MAX. If it cycles off, note the low side when it does. Repost.
BTW, '94s were R134 from the factory
Drifting
Joined: May 2005
Posts: 1,336
Likes: 12
From: Chicago Executive Airport, formerly known as Palwaukee
No-IL Events Coordinator
St. Jude Donor '12-'13-'14-'15-'16-'17
Why do you need to know pressures?
Are you feeling a lack of cooling in the cabin?
What is your temp in the middle vent?
Are you feeling a lack of cooling in the cabin?
What is your temp in the middle vent?
Thread Starter
Racer
Joined: Nov 2011
Posts: 274
Likes: 12
From: Louisburg NC
Center vent shows 58 degrees @ 86 degrees OAT. The AC doesn't work very well when it's 105 outside. 
I'm just trying to make it work better. The car has 120K on it. I suspect the orifice valve may be clogging up.
I'm just trying to make it work better. The car has 120K on it. I suspect the orifice valve may be clogging up.
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Drifting
Joined: May 2005
Posts: 1,336
Likes: 12
From: Chicago Executive Airport, formerly known as Palwaukee
No-IL Events Coordinator
St. Jude Donor '12-'13-'14-'15-'16-'17
I would not condemn any parts at this time.
When was the last time the system was recovered and recharged?
If done many years ago, the following would be my recommendation:
Find someone with an A/C recovery/charging station. Have them recover your freon and recharge the system with the EXACT amount of freon.
IIRC yours should take EXACTLY 2.0 lbs. You can check this against your A/C sticker which can be found on the Evaporator case underneath the radiator coolant expansion tank near the passenger side windshield area.
BTW, not relevant to this particular discussion, but another question. Is this the manual or electronic A/C system? Just wondering.
When was the last time the system was recovered and recharged?
If done many years ago, the following would be my recommendation:
Find someone with an A/C recovery/charging station. Have them recover your freon and recharge the system with the EXACT amount of freon.
IIRC yours should take EXACTLY 2.0 lbs. You can check this against your A/C sticker which can be found on the Evaporator case underneath the radiator coolant expansion tank near the passenger side windshield area.
BTW, not relevant to this particular discussion, but another question. Is this the manual or electronic A/C system? Just wondering.
Drifting
Joined: May 2005
Posts: 1,336
Likes: 12
From: Chicago Executive Airport, formerly known as Palwaukee
No-IL Events Coordinator
St. Jude Donor '12-'13-'14-'15-'16-'17
I bought my CE new. I have the same system you do. C68
I had to replace the high side pressure switch many years ago. I have replaced no other A/C parts.
I have over 128,000 miles.
A month ago I located a very, very small leak in the main hose assembly from the compressor. My system was recovered and recharged a month ago. I am going to order the hose I need when the system loses some of it cooling. So far it has not.
Been in the 90s in Chicago all month. Went to Bowling Green in the middle of June and temps were in the mid to upper 90s.
A/C has been blowing so cold that I could make ice cubes if I had a mind to!
I am telling you all this for a reason. My vehicle has the identical system as your Vette.
I believe your pressures are a little lower than they should be pointing to a lower amount of freon in the system than is needed.
With a total recharge you should have temps in the middle vent in the 40s.
In the old days in my repair shop, we charged systems by the can looking at the pressures as we did so. Now, with the new equipment, the EXACT amount of freon can be used. The EXACT amount of freon will cause any A/C system to work perfectly.
I had to replace the high side pressure switch many years ago. I have replaced no other A/C parts.
I have over 128,000 miles.
A month ago I located a very, very small leak in the main hose assembly from the compressor. My system was recovered and recharged a month ago. I am going to order the hose I need when the system loses some of it cooling. So far it has not.
Been in the 90s in Chicago all month. Went to Bowling Green in the middle of June and temps were in the mid to upper 90s.
A/C has been blowing so cold that I could make ice cubes if I had a mind to!
I am telling you all this for a reason. My vehicle has the identical system as your Vette.
I believe your pressures are a little lower than they should be pointing to a lower amount of freon in the system than is needed.
With a total recharge you should have temps in the middle vent in the 40s.
In the old days in my repair shop, we charged systems by the can looking at the pressures as we did so. Now, with the new equipment, the EXACT amount of freon can be used. The EXACT amount of freon will cause any A/C system to work perfectly.