Video of my AC gauges after work

[jcrubin]

Running 134A at about 70 degrees ambient temp today. Looks within spec and blows cold. any thoughts.

http://www.youtube.com/watch?v=U--NIh1OdlM&feature=c4-overview&list=UUuN48bg_NnD7kMXBkII7aUw

[DMCMW Dave]

Running 134A at about 70 degrees ambient temp today. Looks within spec and blows cold. any thoughts.

http://www.youtube.com/watch?v=U--NIh1OdlM&feature=c4-overview&list=UUuN48bg_NnD7kMXBkII7aUw

High side seems low but if it's working. . .

Belts are noisy, check the idler bearings too.

[David T]

High side seems low but if it's working. . .

Belts are noisy, check the idler bearings too.

I did not hear the compressor cycling, and your pressures are too low. You probably need to add a little more refrigerant and adjust the low pressure switch. Stick a thermometer into the center vents and get at least a 20 degree delta T against ambient. That means you need to see at least 50 degree air at the vents (with an ambient of 70). Is it making water? Set the fan speed to 4, temp to cold, mode to NORM. You should also use fans in front of the radiator for testing purposes. Doors closed and idle at around 1,000 RPM's.

[DMCMW Dave]

I heard it cut out at the end


Sent from my phone

[Bitsyncmaster]

The high pressure is probably low because it's only 70 deg. air temp outside. Try it in the summer.

[jcrubin]

I did not hear the compressor cycling, and your pressures are too low. You probably need to add a little more refrigerant and adjust the low pressure switch. Stick a thermometer into the center vents and get at least a 20 degree delta T against ambient. That means you need to see at least 50 degree air at the vents (with an ambient of 70). Is it making water? Set the fan speed to 4, temp to cold, mode to NORM. You should also use fans in front of the radiator for testing purposes. Doors closed and idle at around 1,000 RPM's.



Yes there was a lot of water coming from under the car.

[DMCMW Dave]

Doors closed .

Why?

[David T]

Why?

I test with the doors closed. If you do it with the doors open you are pulling in hot, humid air and not recirculating. Under certain conditions you might be lucky to see a Delta T of 20. The fact that it is making water is a good sign. Did you zero the gauges before using them?

[lindbergh]

Your low pressure switch is fine, it is cycling at 20psi on the low side as it should. You have pressures about what I have at 8 degrees cooler ambient and mine gets down to the cycling pressure a little quicker than yours without high revs but that's probably because of the colder outside temp. You may be an ounce or 2 low on refrigerant at most but I would not do anything until it gets warmer out and see what the pressures are doing then. I also have the VOV replacement for the orifice tube so that may be making things slightly different as well. I replaced my entire A/C system (everything) over Thanksgiving week. Yours is looking good.

[David T]

Your low pressure switch is fine, it is cycling at 20psi on the low side as it should. You have pressures about what I have at 8 degrees cooler ambient and mine gets down to the cycling pressure a little quicker than yours without high revs but that's probably because of the colder outside temp. You may be an ounce or 2 low on refrigerant at most but I would not do anything until it gets warmer out and see what the pressures are doing then. I also have the VOV replacement for the orifice tube so that may be making things slightly different as well. I replaced my entire A/C system (everything) over Thanksgiving week. Yours is looking good.

20 psi on the low side with R-134 is too low. 150 psi on the high side (remember this is BEFORE the condenser coil which is not really where you should be reading this but that is where they put the high side service port!) is too low also and that tells me you do not have enough refrigerant. On just about any other car I know, the high side service port is AFTER the condenser coil, not on the output of the compressor. A convenient but dumb place to put the high side port. What this means is you are reading the pressure of a hot gas NOT a warm liquid. Big difference, much higher pressures. If the compressor is cycling it is not cycling often enough. Adding gas will only make it worse. You need to adjust the low pressure switch to a higher cut-off pressure so it will cycle more. If you are reading the pressure through the shrader valve maybe the hose is not depressing the pin enough to fully open it so you are not seeing accurate low side pressures. I like to use a core extractor (on the low side) so I do not go through the core during service. On the high side, if you do not use a damping gauge the pulsations and vibrations from the compressor will damage even an expensive gauge quickly. The fact you are blowing cold and making water says you are close. To get all of the capacity the system has you need to fine-tune the pressures by adjusting the amount of refrigerant and setting the low pressure switch. If you do not cycle the compressor eventually you will freeze the evap coil especially when you run the fan at lower speeds.

[DMC5180]

Low Side switch should be set to cut out at about 26-28 Psi with 134a.

[Ron]

20 psi on the low side with R-134 is too low. 150 psi on the high side (remember this is BEFORE the condenser coil which is not really where you should be reading this but that is where they put the high side service port!) is too low also and that tells me you do not have enough refrigerant. On just about any other car I know, the high side service port is AFTER the condenser coil, not on the output of the compressor. A convenient but dumb place to put the high side port. What this means is you are reading the pressure of a hot gas NOT a warm liquid. Big difference, much higher pressures. If the compressor is cycling it is not cycling often enough. Adding gas will only make it worse. You need to adjust the low pressure switch to a higher cut-off pressure so it will cycle more. If you are reading the pressure through the shrader valve maybe the hose is not depressing the pin enough to fully open it so you are not seeing accurate low side pressures. I like to use a core extractor (on the low side) so I do not go through the core during service. On the high side, if you do not use a damping gauge the pulsations and vibrations from the compressor will damage even an expensive gauge quickly. The fact you are blowing cold and making water says you are close. To get all of the capacity the system has you need to fine-tune the pressures by adjusting the amount of refrigerant and setting the low pressure switch. If you do not cycle the compressor eventually you will freeze the evap coil especially when you run the fan at lower speeds.
+1

===================

70F is where the pressure characteristics of R12 and 134a are the same. Pressure readings are to be taken when the clutch cycles out. It looks like it cycled out at ~19psi (low side) and 140psi(high side). The manual calls for 25-32psi (low) and 125-150 (high) at 70F (measured in front of the condensor).

$.02:
You need to turn your cycle switch in (it's cutting out too late & not cycling properly)...THEN you will probably see that you need to add refrigerant to get it back into the 125-150psi (high) range (go for low end since you are using 134a which has higher pressures than R12 as temp rises....).
Ideally, you should set this during higher temps using the charts...at least check it the first time it gets toasty out to avoid over-pressure (not needed when using R12).


Refrigerant/Pressure/Conversion here (http://dmctalk.org/showthread.php?1244-Refrigerant-Temp-Pressure-Chart&p=13935&viewfull=1#post13935)

Manual's chart here, N:09:01 (http://dmctalk.org/showthread.php?7921-AC-Pressure-Charts-Reading-Gauges-(R12-and-Retrofit))