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Old 10-11-2018, 04:46 PM   #26
rsgt
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Re: Reading A/C gauge

Quote:
Originally Posted by Jrainman View Post
YOU can test the POA in the truck
TO test it idle at 1500 rpm
Use a fan and put it in front of condenser (radiater)
unplug the blower motor
gauge on low side reading should be between 28-30 psig

the POA factory setting should be 32 .

there are other things to check also , Air in system
make sure your heater core is not bleeding by
also spray water on the condenser and see if the lowside pressure drops.
Hey, Thanks. I did that and the reading did not change so I guess the poa is bad.
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Old 10-12-2018, 11:03 AM   #27
randy500
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Re: Reading A/C gauge

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Originally Posted by rsgt View Post
Thanks Randy. So if I have a poa valve sitting on the bench I could cap off the discharge hook up my gauge and blow 60 lb on the inlet. Will this let me know if it is free inside?
Don't cap off the end of the POA valve when testing, If you did that the pressure would rise since the POA valve is a pressure regulator, it regulates the pressure inside the evaporator. It keeps the pressure in the evaporator at whatever it is adjusted to.
You adjust the POA using temperature pressure table for the refrigerant used. You want the pressure to be such that the evaporator temperature is just about 32 degrees.
For R12 temperature of 32 degrees the pressure is 30.1
For R134a temperature of 32 degrees the pressure is 27.8
If the evaporator pressure is less than the above figures the evaporator will freeze up, if the pressure is more (such as in your case) the evaporator will not be cold enough to provide cooling.

The POA valve is isolated from atmospheric pressure so you compensate for altitude on your gauge which is affected by altitude.
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Old 10-12-2018, 11:19 AM   #28
randy500
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Re: Reading A/C gauge

Quote:
Originally Posted by Jrainman View Post
YOU can test the POA in the truck
TO test it idle at 1500 rpm
Use a fan and put it in front of condenser (radiater)
unplug the blower motor
gauge on low side reading should be between 28-30 psig

the POA factory setting should be 32 .

there are other things to check also , Air in system
make sure your heater core is not bleeding by
also spray water on the condenser and see if the lowside pressure drops.
I will explain the above tests...

Unplugging the blower motor puts a high refrigerant load on the evaporator without airflow across it, the POA valve should not allow the pressure to fall below the POA set point. If it were to fall below the set point the evaporator would freeze the condensation in the air forming ice on the outside of it which would prevent air from flowing through the evaporator which would cause a no cooling condition.

The factory POA setting is not 32, it is as I previously explained.

Heater core bleeding means the core is getting hot water when in the AC mode which hinders vent temperatures. Test the hot water valve or pinch off the heater hose. This is not your problem at this point.

Spraying water on the condenser is a test for condenser capacity. Your high side pressure is normal so this test is not necessary. High side pressure does not affect low side pressure in a POA valve system with a properly functioning expansion valve. Your expansion valve at this point does not seem to be a problem.
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Old 10-12-2018, 11:22 AM   #29
randy500
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Re: Reading A/C gauge

I have assumed you know how much refrigerant is in the system...
When was it charged and what type of refrigerant?
How much refrigerant is in the system?
What does the sight glass look like, nothing, bubbles or clear. Or bubbles then clears up with rpm increase.
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Old 10-13-2018, 05:22 AM   #30
Jrainman
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Re: Reading A/C gauge

Quote:
Originally Posted by randy500 View Post
Don't cap off the end of the POA valve when testing, If you did that the pressure would rise since the POA valve is a pressure regulator, it regulates the pressure inside the evaporator. It keeps the pressure in the evaporator at whatever it is adjusted to.
You adjust the POA using temperature pressure table for the refrigerant used. You want the pressure to be such that the evaporator temperature is just about 32 degrees.
For R12 temperature of 32 degrees the pressure is 30.1
For R134a temperature of 32 degrees the pressure is 27.8
If the evaporator pressure is less than the above figures the evaporator will freeze up, if the pressure is more (such as in your case) the evaporator will not be cold enough to provide cooling.

The POA valve is isolated from atmospheric pressure so you compensate for altitude on your gauge which is affected by altitude.
I Apologize ,I was just trying to give some examples of some general test procedures to someone with limited refrigerant backround can do when having a no cooling issue , My post in no way said to the OP this is your issue . I will make sure never to post anything here on the subject of Dichlordifuoromethane again since you seem to be the authorty on the subject Here.
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