And so it begins................

[highperf4x4]

Ok, I'm troubleshooting the A/C now so I'll have to get back to the body work later. For some reason it decided to stop cooling even though it isn't low on freeon. If anybody knows someone with experience in dealing with POA a/c systems let me know.

[70 Suburban]

i would start by layin hands on it.. realy grab the lines. make sure there is no sudden temp drop. do the same on the condensor. make sure that there is nothing blocking the evap.. thats where I would start. then leme know what your pressures are. Is your compressor cycling or is it staying off, or on...

[highperf4x4]

That's the thing with a POA system, the compressor doesn't cycle. It just stays on. I haven't been able to check the high side pressure yet but the low side was reading about 25psi

[70 Suburban]

the compressor will cycle if there is to little freon or if the pressure on the high side is to high it will shut the compressor off. pressure will drop then it will come back onl. It looks like cycle.

[joe231]

25 on the low side is pretty low, it needs to be at least 35-40...
BTW, what is POA?
oh wait....are you running R-12 or R-134? that makes a difference in pressures.
I have seen the compressor go bad and it would still run but it would not build any pressure on the high side.

[JohnC]

That's a Hyperism Joe. Guess he need's to have a quick guide for us!

Man I wish I knew more about A/C. Is it still the old R12 system, or have you converted to 134A?

[70 Suburban]

Poa should be about 28-30 max.. But you can update it to ccot

[70 Suburban]

If you are running 134 did you adjust the poa?

[joe231]

oh, found some info

Originally Posted by youracauthority.com

Pilot Operated Absolute (POA) Valve

Like the suction valve, the POA valve is a suction throttling device that is located at the outlet of the A/C evaporator and is used to control the amount of compressor suction on the evaporator.

The POA valve was used on some General Motors and Ford air conditioning systems through the 1970's. On these A/C systems, the compressor would run constantly whenever the A/C system was on. Under certain operating conditions, less compressor suction was required on the evaporator. The POA valve would then close off the flow of refrigerant, effectively reducing the amount of compressor suction.

Originally Posted by youracauthority.com

Cycling Clutch Orifice Tube - CCOT A/C System


General Motors introduced the cycling clutch orifice tube A/C system in the 1977 model year. The unique advantage to having a cycling clutch with a fixed orifice tube was that now, the only moving part on the A/C system would the A/C compressor. The fixed orifice tube, which provides a one size, fixed opening for the flow of refrigerant into the expansion valve had replaced the typical expansion valve or TXV valve that opened and closed to control the refrigerant flow into the evaporator.

The fixed orifice tube means that there is always a flow of refrigerant into the evaporator. In order to control the evaporator pressure and maintain the coldest possible temperature in the evaporator without freezing the condensation, the system was designed to cycle the compressor on and off.

The cycling clutch system meant that the typical normal pressure gauge readings of a properly operating system would have a wider range. Of course, the low side pressures would be at their lowest just before the compressor cycles off while the high side pressures would be at their highest. As soon as the compressor clutch disengages, the high pressures start to drop while the low pressures increase. That happens because the fixed orifice tube is always allowing refrigerant to flow through it, regardless of whether the compressor is on or off. As soon as low pressures began to rise causing a higher temperature in the evaporator, the compressor would cycle back on to pull the pressures and temperature down on the low, once again increasing the pressures on the high side. The cycle continues in a controlled manner that maintains mean or average pressures in the evaporator so that the A/C system can provide maximum cooling performance with the minimum number of moving components.

Understand that the CCOT or fixed orifice tube system is still slightly different than typical cycling clutch systems. In other system designs, expansion valves are still used to control the flow of refrigerant into the evaporator. Those typical expansion valves open and close to monitor refrigerant flow while the compressor cycles on and off to maintain proper evaporator pressures. The orifice tube system utilizes the fixed opening in the orifice tube which maintains a constant flow of refrigerant.

so it sounds to me like your POA valve might be malfunctioning?

[mrein3]

Originally Posted by highperf4x4

That's the thing with a POA system, the compressor doesn't cycle. It just stays on. I haven't been able to check the high side pressure yet but the low side was reading about 25psi

IF everything else is working right, and IF you are still running R12, you need to add some. You should be in the 28-30 range.

[JohnC]

Great info Joe!

[TheSebring]

Trying breaking off the line to the condenser and see how long it sprays everywhere. If it sprays for over a minute, you HAD plenty.

[joe231]

that method is not for the feint of heart

[highperf4x4]

You guys are killing me........

[highperf4x4]

Originally Posted by 70 Suburban

the compressor will cycle if there is to little freon or if the pressure on the high side is to high it will shut the compressor off. pressure will drop then it will come back onl. It looks like cycle.

Mine has never shut off on it's own. I turned it on empty after I installed the compressor and it engaged, I had to shut it off and add the oil charge before I turned it on again. You got any idea where the low pressure shut off should be?

Originally Posted by joe231

25 on the low side is pretty low, it needs to be at least 35-40...
BTW, what is POA?
oh wait....are you running R-12 or R-134? that makes a difference in pressures.
I have seen the compressor go bad and it would still run but it would not build any pressure on the high side.

I'm running 134 in it. I don't even get 35-40 on my 4x4 though and it's r12 unless you're talking about after it cycles off and then it climbs to about 55. However, the 72 doesn't cycle.

Originally Posted by JohnC

That's a Hyperism Joe. Guess he need's to have a quick guide for us!

Man I wish I knew more about A/C. Is it still the old R12 system, or have you converted to 134A?

I wish you knew more too!

Originally Posted by 70 Suburban

Poa should be about 28-30 max.. But you can update it to ccot

I"m thinking about making the switch. Have you done it before?

Originally Posted by 70 Suburban

If you are running 134 did you adjust the poa?

It was a redneck adjustment. I took the valve out and turned it counterclockwise a half turn! I know, ..... don't say it.

Originally Posted by joe231

oh, found some info





so it sounds to me like your POA valve might be malfunctioning?

me thinks so too.

Originally Posted by mrein3

IF everything else is working right, and IF you are still running R12, you need to add some. You should be in the 28-30 range.

Not running r12 but it was reading 25 even before I adjusted the POA. I won't know what it is now until I charge it again tomorrow

Originally Posted by TheSebring

Trying breaking off the line to the condenser and see how long it sprays everywhere. If it sprays for over a minute, you HAD plenty.

Stay away from my truck.

[JohnC]

Originally Posted by TheSebring

Trying breaking off the line to the condenser and see how long it sprays everywhere. If it sprays for over a minute, you HAD plenty.

Not everyone has your method of trouble shooting!

Originally Posted by highperf4x4

I wish you knew more too!

That's why I'm here is to learn. Teach me grasshopper!

[highperf4x4]

I will just as soon as I figure it out. New compressor just locked up so you may want to learn from someone else.....................

[joe231]

ouch, that sucks

[scotts62]

Originally Posted by highperf4x4

I will just as soon as I figure it out. New compressor just locked up so you may want to learn from someone else.....................

Scream WARRANTY!

[TheSebring]

I'll tell you what, it may be an unorthodox way of trouble shooting, but I figured out that it had plenty of freeon. So it works.

[JohnC]

that you did Blake that you did.

[highperf4x4]

Originally Posted by TheSebring

I'll tell you what, it may be an unorthodox way of trouble shooting, but I figured out that it had plenty of freeon. So it works.

The only thing you flippin figured out is where the SECOND leak is. Now go polish some wheels!

[JohnC]

Ah those priceless Father Son moments!

[TheSebring]

Priceless my butt.

Price of 4 barrel intake:200

Price of 4 barrel Edelbrock carb:300

Price of a new spare because the old one was used to try and tighten up new lug studs(and the old one was the FACTORY):100

[highperf4x4]

Originally Posted by TheSebring

Priceless my butt.

Price of 4 barrel intake:200

Price of 4 barrel Edelbrock carb:300

Price of a new spare because the old one was used to try and tighten up new lug studs(and the old one was the FACTORY):100

oh bull crap. Go to a flippin mopar forum and tell them you need one of the old 5 lug 14" wheels and they will give 10 of them for free. I threw the other 4 from this car in the trash years ago.