| Re: Dash A/C recharge [message #88744 is a reply to message #88724] |
Tue, 15 June 2010 19:28   |
Bob de Kruyff
Messages: 4260
Registered: January 2004
Location: Chandler, AZ
Karma: 1
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""Duracool gives a little more cooling but a possible bigger issue is, because of the larger molecule it causes the compressor to build up considerably less head pressure, so less stress on it. I run 134 in my coach because its dash air is not OEM and has all new components. Its ice cold. I ran Duracool in my corvettes. ""
I'll probably switch at some point but I'm waiting for something to leak down or require attention before I go to the trouble 
Bob de Kruyff
78 Eleganza
Chandler, AZ
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| Re: Dash A/C recharge [message #88754 is a reply to message #88744] |
Tue, 15 June 2010 20:09 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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Bob
After I fixed the leak in my 4 runner I charged it with Duracool and while removing the gages I had a problem with a schrader valve causing me to loose some of the charge. I now had 20 lbs suction pressure and a not so cold suction line I also had no more Duracool so I just completed the charge with 134 out of my 30 lb jug to bring the suction to 25-30 lbs and a cold suction. I don't expect any problems and it's been awhile. I know some of you will say 20 lbs is where it should be but not in this case if the suction pressure at 20 lbs is not cold and sweaty you are under charged.
Roy
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Dash A/C recharge [message #88767 is a reply to message #88755] |
Tue, 15 June 2010 21:38 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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You are correct if the suction pressure is too low you will freeze up the evaporator coil with any refrigerant be it car,truck, house commercial etc. Pressure relates to temperature
there are close similarities between 12,134 and Duracool. I believe 134 is a tad higher then 12 and Duracool may be a tad lower then 12. If you were to charge your system and the suction line were cold and the pressure were say 25 lbs. Another system could be 30 lbs under similar circumstances. Assuming both expansion valves were good most likely the system with the lower pressure is moving less air thru the coil and it is going to be colder. What you need to keep in mind is if you don't have enough refrigerant in the system the suction line will not be cold and sweaty that means the coil is not cooling to its full capability and the pressure is going to be low and yes it will start icing up. In the GMC there is a thermostat in the evaporator section that cycles the compressor off when the air gets too cold then re-energizes the clutch when the air warms a bit.
I took mine out and installed a remote bulb thermostat with the bulb clamped to the suction line and set it at 33 degrees this way it rarely cycles the compressor and still prevents freeze up.
Roy
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: Dash A/C recharge [message #88794 is a reply to message #88426] |
Wed, 16 June 2010 04:58 |
Rusty
Messages: 197
Registered: October 2005
Location: Philadelphia Pa
Karma: 0
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Oh ok. I thought the larger molecule meant it was easier to pressurize but I fergot I flunked chemistry in kollege
Rusty
75 Glenbrook
Philadelphia Pa
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| Re: [GMCnet] Dash A/C recharge [message #88826 is a reply to message #88773] |
Wed, 16 June 2010 11:28 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Emery
I'm going to have to disagree on that one. There was no 12 or 134 in the system of the 4 runner it was all evacuated. 20 lbs suction pressure of Duracool in the system left me with an evaporator that was not operating at its rated capacity. In other words it was short of charge. If you check the vapor pressure chart Duracool is around 8 degrees coil refrigerant temp at 20 lbs. 134 would be around 12 degrees. At 30 lbs suction the temp is around 20 deg for the Duracool and 28 for 134 which shows the Duracool is more efficient as far as cooling goes but my 4 runner needed more charge to fill the coil to capacity. The small amount of 134 added to the Duracool only amounts to 2 or 3 lbs of pressure difference between all Duracool or a mix. The actual coil air temperature is definitely higher then the refrigerant temp depending on the amount of air moving thru the coil. It is generally not in ones best interest for the coil fins to be below freezing or the coil will start to ice up especially in humid areas of the country. This is what happens when people set there home or business thermostats below 68 degrees. Many times I had to add an evaporator temperature control like in the GMC so I wouldn't have to come back and defrost these units. I am sure when you charged systems to 20 lbs suction pressure the suction line was cold and sweating or you would have been under charged. We all know the GMC doesn't move a great amount of air thru the evap coil in stock form. This will relate to a lower suction pressure with a fully charged system. A fully charged 134 system would have a suction pressure higher then 12 and 12 would be a little higher then Duracool but the airflow thru all of them will have an effect on the final suction pressure and air temperature leaving the coil.
Roy
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: Dash A/C recharge [message #88859 is a reply to message #88742] |
Wed, 16 June 2010 15:16 |
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roy1 wrote on Tue, 15 June 2010 17:19]George,
If you want a set of gages I have a set you can have but they are not shiny new.
Roy
Good deal Roy, I'll give you a call and arrange. That is an excellent way to discourage me from buying Harbor!
Thanks very much.
geo groth '73 260 Sequoia
Carson City Nevada 89703
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| Re: [GMCnet] Dash A/C recharge [message #89065 is a reply to message #88773] |
Thu, 17 June 2010 22:06 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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Hey Emery I had a different one today I charged a Chevy Tahoe this afternoon that was fully charged with 134A at around 20-22 lbs suction this one had an orifice rather then an expansion valve.
Roy
Roy Keen
Minden,NV
76 X Glenbrook
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