A/C Pressure Isssue?
Thread Starter
Heel & Toe
Joined: Oct 2020
Posts: 24
Likes: 0
A/C Pressure Isssue?
I have a 1980 Corvette with an A/C question. The new Delco A/C Compressor works great, air is about 40 degrees on an 80-degree day. However, my a/c manifold gauge will not read over 50 PSI on the high side fitting of the compressor. I swapped two compressors, a new evaporator, a condenser, and a receiver. Still shows 50 PSI or less. Help me keep my sanity. Since it works, just leave it alone. A/C Ninja is appreciated!
Team Owner
Joined: Jan 2007
Posts: 53,648
Likes: 878
From: Southern Cal Ca
St. Jude Donor '22
if low side is reading right and it cools, then high side must be "high pressure"
double check your gauges valve settings and make sure the low side isn't
bleeding into highside gauge.
I have 2 sets of gauge and hoses.
1 set physically by design doesn't allow high and low to mix.
1 set has valves to separate them.
double check your setup
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,095
Likes: 4,449
From: Marlton NJ
Must be a gauge problem.
If you are getting a 40* drop on an 80* day, it works great.
Leave it alone.
To really get an AC cold, like yours, it is the low side that you need to watch hard, and it needs to go as low as possible. Lower = colder vent temps.
Then it cycles off. Or the POA valve opens/closes.
It really needs to hit below 40# before it cuts off, ~29# is ideal. That gets your evap core down to right around 34*.
Sorry pics will not load today.
If you still have the original POA system, not a cycle switch system, they monitor evap temp and modulate the low pressure by opening or closing the orifice. Totally different system. And pressures. Keep it original as long as it works good, but the POA valves often jam up.
Then convert it to R134 & a cycle system. Almost no one will ever know and you can tune the low psi cutoff / vent temp.
If you are getting a 40* drop on an 80* day, it works great.
Leave it alone.
To really get an AC cold, like yours, it is the low side that you need to watch hard, and it needs to go as low as possible. Lower = colder vent temps.
Then it cycles off. Or the POA valve opens/closes.
It really needs to hit below 40# before it cuts off, ~29# is ideal. That gets your evap core down to right around 34*.
Sorry pics will not load today.
If you still have the original POA system, not a cycle switch system, they monitor evap temp and modulate the low pressure by opening or closing the orifice. Totally different system. And pressures. Keep it original as long as it works good, but the POA valves often jam up.
Then convert it to R134 & a cycle system. Almost no one will ever know and you can tune the low psi cutoff / vent temp.
Melting Slicks
Joined: May 2002
Posts: 2,717
Likes: 121
From: Sulphur LA
St. Jude Donor '05-'06,'11,'13-'14,'16,'18,'19,'24, '25
If your getting 40* air at the vents then either your gauges, service port or hose is not functioning correctly. Can you take a picture of the service port and its location in the system, the high side service port should be between the compressor discharge and the orifice tube, usually after the condenser.
Where is the service port located that you are using to see the high side pressure?
Neal
Where is the service port located that you are using to see the high side pressure?
Neal
Le Mans Master
Joined: Jan 2001
Posts: 6,743
Likes: 1,385
brg1
I concur. If you have 40°F at the outlet vents leave it alone. You might want to spring for some new gauges though.
I would suspect faulty gauges or operator error since you have such nice cold temperatures.
I concur. If you have 40°F at the outlet vents leave it alone. You might want to spring for some new gauges though.
I would suspect faulty gauges or operator error since you have such nice cold temperatures.
Must be a gauge problem.
If you are getting a 40* drop on an 80* day, it works great.
Leave it alone.
To really get an AC cold, like yours, it is the low side that you need to watch hard, and it needs to go as low as possible. Lower = colder vent temps.
Then it cycles off. Or the POA valve opens/closes.
It really needs to hit below 40# before it cuts off, ~29# is ideal. That gets your evap core down to right around 34*.
Sorry pics will not load today.
If you still have the original POA system, not a cycle switch system, they monitor evap temp and modulate the low pressure by opening or closing the orifice. Totally different system. And pressures. Keep it original as long as it works good, but the POA valves often jam up.
Then convert it to R134 & a cycle system. Almost no one will ever know and you can tune the low psi cutoff / vent temp.
If you are getting a 40* drop on an 80* day, it works great.
Leave it alone.
To really get an AC cold, like yours, it is the low side that you need to watch hard, and it needs to go as low as possible. Lower = colder vent temps.
Then it cycles off. Or the POA valve opens/closes.
It really needs to hit below 40# before it cuts off, ~29# is ideal. That gets your evap core down to right around 34*.
Sorry pics will not load today.
If you still have the original POA system, not a cycle switch system, they monitor evap temp and modulate the low pressure by opening or closing the orifice. Totally different system. And pressures. Keep it original as long as it works good, but the POA valves often jam up.
Then convert it to R134 & a cycle system. Almost no one will ever know and you can tune the low psi cutoff / vent temp.
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