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Topic: Service of Air Conditioning freon (Read 960 times) previous topic - next topic

Service of Air Conditioning freon

How much freon  does the 40' U300 (6v92) require.

I am having trouble getting the temp below 60* F.
I just switched to R134A, new compressor, receiver/drier and Ternary sw. Will hold 30" vacuum for over 3 days, so no leaks.

Only small infrequent bubbles in sight gage, fan are cycling, but cannot observe the compressor clutch to check cycling.
1993 U300, 6v92
build 4366
USAF retired, Flight Engineer, C124, C130
 ATP, A & E.  & ex AI

Re: Service of Air Conditioning freon

Reply #1 –
Bill, What pressures are you seeing on your gauges ?  It is possible to overfill with R134 which will cause expansion valve to not work properly. I would rely on gauge pressures more than amount of refrigerant.  You should see on the low side somewhere around 35 to 40 PSI which will translate to about 40 degrees at the evaporator. You can see the coompressor is cycling as the gauge pressures vary or to see if compressor is cycling hook up a test lite at the tri switch and watch it cycle on and off.  Also you have either a freeze stat or thermo type switch at the evaporator, you can bypass it with a jumper to make the compressor run continuously.  Don't try to add refrigerant til there are no bubbles, R134 will most likely show some bubbles when working correctly.  When I charge mine I watch bubbles and just as they start to not appear I quit and then watch gauges.  This is not a simple process and with our coaches the long run of refrigerant line can complicate things.
Finally, Trying to analyze the cooling system in outside temperatures of less than 75 or 80 degrees is hard to do.
Gary B

Re: Service of Air Conditioning freon

Reply #2 –
Quote from: Bill Chaplin –
How much freon  does the 40' U300 (6v92) require.

I am having trouble getting the temp below 60* F.
I just switched to R134A, new compressor, receiver/drier and Ternary sw. Will hold 30" vacuum for over 3 days, so no leaks.

Only small infrequent bubbles in sight gage, fan are cycling, but cannot observe the compressor clutch to check cycling.

Per Mark Harvey Foretravel Director of Warranty Services
Dash Air Conditioner Refrigerant and Oil Capacity
If your dash air system requires maintenance, find a qualified automotive AC repair shop. They will have the specialized equipment and knowledge to make a proper repair. You are likely to find one of the first questions you will receive from your qualified AlC repairman is: What are the manufacturer's recommendations for the refrigerant capacity?

Beginning with Year model 1994 the refrigerant (R134a) capacity for all coaches is 5.0 Ibs or 80oz.

The typical recharge method is to initially fill the system to approximately 90% of capacity and finish the filling process according to monitored high and low pressures along with evaporator intake and output temperatures.

If your system needs to be evacuated for repair, the amount of oil that is recovered during evacuation should be added back into the system at recharge. On a system that may have been flushed or due to severe leaks, has lost all of its refrigerant charge, it is recommended to add 1 oz. of synthetic PAG 10 or PAG 20 oil per 10ft of coach length during the refrigerant recharge process in addition to the oil that is in the compressor. (Example 40 ft. coach length =4 oz. oil)

Most compressors have a data tag indicating the oil capacity for that particular compressor. This is the compressor oil capacity only.
The selected media item is not currently available.Barry BEAM #16014
2003 U320 40' AGDS
Beamalarm, Foretravel technical help and specifications
"Whatever the mind can conceive and believe, it can achieve"

Re: Service of Air Conditioning freon

Reply #3 –
Bill,

This past summer I recharged my dash AC.  It had already been converted to R134A by the one of the prior owners.  I kept filling the system ( at the low side) until I reached about 50 psi and the gauge was almost in the red.  The compressor then kicked on and the fans in the front started working. It started cooling and everything was okay. Not "ice" cold but comfortable when driving.  If your controls are like mine, make sure sure the compressor button is pushed in.  I also noticed a hose had become disconnected under the dash blowing air inside the dash! It took at least 4 12oz cans to do the job as the system was completely leaked down.  Today the outside temp is 70 and I measured 64 degrees at the vents.  The gauge shows no leakdown and the system has stayed charged for almost 6 months.
 
In the minnie winnie I still own,  there is a privacy curtain that can be  stretched across the front just behind the pilot and co-pilot seats that I would use on very hot days when driving that would keep the cab much cooler rather than having all that air flow towards the back.  I think this could be easily accomplished with a couple of curtains and some button snaps or velcro strips to help recirculate much less warm air up front. Maybe someone has done this already.

Jerry
The selected media item is not currently available.
Jerry and Cindy Maddux
1993 U300/36WTBI DD6v92TA
build 4271  "Miss Lou"
1995 suzuki sidekick 4x4 toad
Gulfport, Ms

"Pride of Ownership"

Re: Service of Air Conditioning freon

Reply #4 –
Bill,
I had same , caused by dead fan fan motor on condenser.  Replaced fan, temp went to 48f and all is well.
Dave M

Re: Service of Air Conditioning freon

Reply #5 –
Quote from: coastprt –

In the minnie winnie I still own,  there is a privacy curtain that can be  stretched across the front just behind the pilot and co-pilot seats that I would use on very hot days when driving that would keep the cab much cooler rather than having all that air flow towards the back.  I think this could be easily accomplished with a couple of curtains and some button snaps or velcro strips to help recirculate much less warm air up front. Maybe someone has done this already.
Jerry
We made some curtains for this purpose. Bought an expansion pole to put between the cabinets on either side. My wife sewed the top of curtains so the pole would slide thru. We can take it down and stowed when not in use. What a difference it made to the cooling up front.
The selected media item is not currently available.Barry BEAM #16014
2003 U320 40' AGDS
Beamalarm, Foretravel technical help and specifications
"Whatever the mind can conceive and believe, it can achieve"

Re: Service of Air Conditioning freon

Reply #6 –
Quote from: coastprt –
I kept filling the system ( at the low side) until I reached about 50 psi and the gauge was almost in the red. 

The low pressure switch normally turns off compressor when pressure in the system is too low. When system is empty of refrigerant, it is important to bypass the low pressure switch so compressor will run while filling with refrigerant. It is not normal to fill until pressure switch turns on compressor.

Shorting the low pressure electrical contact will allow 12-volts to bypass the low switch when ignition and AC switch is turned on. Another ways is to unplug the compressor and connect 12-volts directly to compressor. These temporary bypass methods are used until enough coolant is 'sucked' into the system to keep the low pressure switch closed on its own.

Re: Service of Air Conditioning freon

Reply #7 –
With some R12 to 134A conversions the system will not be as efficient due to the condenser being to small. We have done several conversions on older R12 systems and have done good to get 50 degree discharge air @ 90 degrees outside temp. Make sure your condinser coils are good and clean.
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Service of Air Conditioning freon

Reply #8 –
Bill, last year I had over filled my freon, if a little is good, too much is better!!!. The guys at Foretravel reduced the freon level to the right amount and dropped the output temperature of the A/C an additional 10 degrees.
The selected media item is not currently available.Kent Speers
Locust Grove, OK
1993 U300 SSE 40' (Restored at FOT 2009) Build 4323
720 watts Solar
6V92TA DDEC Silver Engine
2014 Subaru Outback