Pilot Operated Absolute (POA) Valves are the Suction Valves that were used on most mid 60's to mid 70's GM vehicle air conditioning systems and on some 70's Ford systems.
"Suction Valves are air conditioning valves mounted to the Evaporator's suction (top) outlet to regulate air conditioning system pressures and prevent the Evaporator from freezing".
Frequently Asked Questions
What does a POA Valve do? [more]
All air conditioning systems have something built into the system to prevent the Evaporator from getting so cold that it freezes. In some systems, this mechanism is a thermostat, but in most mid 60's to mid 70's GM vehicles and some 70's Ford vehicles, it's a POA (Pilot Operated Absolute) Valve.
A thermostat prevents the Evaporator from freezing by cycling the compressor on and off based on Evaporator temperature. A POA Valve prevents the Evaporator from freezing by by-passing excessive system pressure. Note that in a POA Valve type system, the Compressor runs constantly whenever the air conditioning system is operating.
As long as the Evaporator pressure remains above a predetermined level, the POA Valve remains open, allowing Refrigerant to flow freely out of the Evaporator. When Evaporator pressure drops below that level, the POA Valve closes and the Refrigerant flow out of the Evaporator is restricted. The pressure in the Evaporator then increases, which increases the temperature in the Evaporator and prevents the Evaporator from freezing.
Most POA Valves also regulate Evaporator pressure through a pressure equalization line connection back to the Expansion Valve that balances the pressure of the Refrigerant entering the Expansion Valve and thereby regulates the amount of Refrigerant the Expansion Valve allows into the Evaporator.
The POA Valve also aids circulation of oil to the Compressor through an oil bleed line connection to the bottom of the Evaporator through which oil that collects at the bottom of the Evaporator is forced by Evaporator pressure back into the Refrigerant loop.
A POA Valve operates independently of atmospheric pressure and is not affected by changes in altitude.
How does a POA Valve fit into the air conditioning system? [more]
The POA Valve mounts directly to the Evaporator's suction outlet, with normal flow of Refrigerant right through the valve's female end fitting and out the male end fitting. Some Ford POA Valves have two or four additional fittings but most of them and all the GM POA Valves have three additional fittings:
(1) A male charge fitting (for connection to an external manifold gauge);
(2) a male oil bleed line fitting (which connects to the long skinny line from the Evaporator Coil); and
(3) A female pressure equalization fitting (which connects to the male nut on the Expansion Valve capillary tube).
Are there different types of POA Valves? [more]
Depending on the model, General Motors cars & trucks used one of three different POA valves, all of which were made in Frigidaire, then Delco versions. Depending on the model, Ford used one of nine different POA valves, all of which were made only in Delco versions. Delco valves cannot be rebuilt, but we may be able to recondition yours or offer an NOS replacement.
Any POA Valve issues when restoring car? [more]
If your air conditioning system has not been operating for a while, it is probably best to test your POA Valve as part of the restoration of your vehicle.
Also, if you are converting to 134a Refrigerant, your POA Valve will need to be recalibrated to by-pass at a different rate than it did with the old R12 Refrigerant.
You can send your POA Valve to us and we can test it for you. If it passes a series of tests, we can recondition and recalibrate it for you. If it is a Frigidaire Valve and fails any of the tests, we can completely rebuild it. See the Recondition and Rebuild questions below.
Is my POA Valve failing? [more]
To find out, most customers choose to send us their POA Valve and let us test it. If it passes a series of tests, we can recondition and recalibrate it for you. If it is a Frigidaire Valve and it fails any of the tests, we can completely rebuild it. See the Recondition and Rebuild questions below.
Alternatively, you or your mechanic may be able to determine if your POA Valve is failing during system evaluation using gauge manifolds. A POA Valve will generally fail in the open position, letting high pressure vapor into what should be the low pressure side of the A/C system. If the POA Valve is failing, you'll have little or no cold air coming out the vents when the air condition system is operating and the high side reading will be normal but the low side reading will be high. (Because the failing POA Valve is letting high pressure vapor into the low side of the system).
A properly functioning POA valve equipped system with R12 refrigerant will have a low side readings on POA valve of right around 30psi, while systems using 134a refrigerant should read right around 20psi, once calibrated.
High side readings can vary depending upon the refrigerant, outside temperature and humidity but should generally fall within the following ranges:
|High Side Readings
|Outside Air (Ambient)
|High Side Readings
|Outside Air (Ambient)
Suggestions for a failing POA Valve? [more]
If your POA Valve is failing, first determine if it is an original Frigidaire. See "Are there different types of POA Valves?" above. If it is, send it to us and we can either rebuild it and return it to you or send you a rebuilt replacement. See "What is POA Valve Rebuilding?" below.
If it is not an original Frigidaire, it cannot be rebuilt and you'll need to order a replacement from us.
Any POA Valve issues when converting to 134a? [more]
If you are converting to 134a Refrigerant, your POA Valve will need to be recalibrated to by-pass at a different rate than it did with the old R12 Refrigerant.
You can send your POA Valve to us and we can test it for you. If it passes a series of tests, we can recondition and recalibrate it for you. If it is a Frigidaire Valve and it fails any of the tests, we can completely rebuild it. See the "What is POA Valve Reconditioning?" and "What is POA Valve Rebuilding?" questions below.
What is POA Valve Reconditioning? [more]
POA Valve Reconditioning is the restoration service we perform on a POA Valve that passes our initial tests. We can perform these services without having to cut the POA Valve open. POA Valve Reconditioning includes:
- Initial tests
- Flush clean
- Calibrate for R12 or 134a
- Zinc plate
- Final tests
What is POA Valve Rebuilding? [more]
POA Valve Rebuilding is the restoration service we perform on a Frigidaire POA Valve that fails any of our initial tests. To perform these services, we must cut the POA Valve open in order to repair it. (We then weld it back together, pressure test and zinc plate it once repairs are finished).
Rebuilding is only available on original Frigidaire Valves. It is not available for Ford Valves or Delco replacement valves. To understand the difference, see "Are there different typed of POA Valves?" above.
POA Valve Rebuilding includes:
- Initial tests
- Cut open
- Clean and repair or replace damaged parts
- Replace seals
- Reassemble and weld back together
- Test and calibrate for R12 or 134a
- Zinc plate
- Final tests
What's a Core Charge? [more]
Since many rebuilt & reconditioned parts are no longer made, our ability to provide them on an outright basis depends on our ability to maintain inventory known as cores. The sale of a rebuilt or reconditioned part often carries a "core charge," which is a form of deposit that is paid until your original part can be returned, or as a means of purchasing a part without returning anything if you don't have the core to return to us.
For example, let's say you want to buy a rebuilt POA valve, but you haven't removed the old valve from the car yet. You pay an additional core charge up front when you buy the valve. Once the old valve is removed from your car and replaced, you return the old valve with your receipt (which includes the core charge), and as long as the old part is in acceptable condition, the core charge is refunded.