dash air charge

[pashir]

I think the dash air in my diesel pusher need a shot of r134a. what are the optimum pressures on the low and high side?
thanks

[dougrainer]

J-Rooster wrote:
Paul, I sent you a PM today, and here is a follow up on my dash air system that was charged today. It took 2 gallons of R134a refrigerant, my mechanic put a temperature gauge in the dashboard vent and it was reading 46* on the psi and he said that 200 was high and 60 low. Good Luck with your system. Take Care, John

2 GALLONS?????? I think you made a mistake on the amount:h Doug

[J-Rooster]

Paul, I sent you a PM today, and here is a follow up on my dash air system that was charged today. It took 2 gallons of R134a refrigerant, my mechanic put a temperature gauge in the dashboard vent and it was reading 46* on the psi and he said that 200 was high and 60 low. Good Luck with your system. Take Care, John

[JumboJet]

There are cans of R134a that include oil, sealant, and freon. The 12 ounces on the can will not be 12 ounces of freon.

I finished a re-charge of my system yesterday. I used a real set of gauges and charts available for my chassis.

I saw refill cans in the auto parts store that have the gauge with the green zone and psi up to 55. This will be the suction pressure - the blue hose. R134a systems will not let you connect the hoses incorrectly (fittings are sized differently) unless you are using old R12 gauges and R12 to R134a adapters and are color blind.

[rgatijnet1]

You only need a vacuum pump if your AC system is completely out of freon. If that is the case, then you need to replace the dryer also, as well as completely evacuate the entire system. You will also probably need oil as well. But first you would have to find the leak.
If there is still freon in the system, then you can add freon without the gauges, by using just a thermometer in the dash outlet.
Add the freon slowly while watching the output air temperature, with the AC fan on high. Once the temperature reaches it's lowest temp, and starts to increase, then stop adding freon. The little bit of freon that you lose when disconnecting the hose will probably get it just right.
I've used this method for years, in all kinds of outside temperatures, and started using it when the shift was made from R12 to R134a.

[J-Rooster]

pashir wrote:
J-Rooster
thanks and I'll be watching for that report.
I'm a career do-it-yourself.
Paul

Paul, I'll send you a PM when my coach is finished on Wed. and let you know what the mechanic said!

[pashir]

Thanks to all of you for your answers.
I don't have an IR temp gun.
I didn't know about the loaner vac pump at autozone, but I'll sure use it.
The approximate pressures should be a good start.
I really appreciate the help from all of you.
Paul

[dougrainer]

azpete wrote:
as teachers pet noted, his unit had a 30 foot line in the system. there is the main problem with using weights for recharging motorhome systems. the hoses are added by the manufacturers, and some have no idea how long they are. and they vary from model to model. so weight numbers supplied are a hit or miss situation.
if you have partial cooling, there is a 95% chance of no leak. just add some freon with a dye and check it with a uv light days later.
if there is a leak, repair it, evacuate the system, and recharge it, using the pressures as a guide. you can get a vacuum and the guages,at autozone on loan.
when the pressures are near what they should be, check the sight gauge if present. keep adding till it clears up, or the a/c cools to suit you.
i know this is a backyard mechanics approach, but is works for me, and i have used it with much success on all my coaches. just dont over do it with the freon. moderation in all things.
having said all this, most of you know that the dash air does a poor job of coolng the whole coach.
i use the generator and run the basement air on my meridian dp. it doesnt affect the mileage that much. no more than running the dash air. all of it takes fuel.

1. As I stated, 134a systems will ALWAYS have bubbles in the sight glass when fully charged
2. A COMMON misconception, when comparing Motorhome (rear engine) systems with Auto's is somehow there will be a LOT more coolant needed because of that 30/40 foot hose runs. NOT SO, there will be at most a .5 lb difference due to the run.
3. PRESSURES will NEVER be different between a Motorhome due to the length of the AC lines front to rear.
4. ALL Automotive systems Leak. It just may take years to finally show up and not cool. You then recharge as long as the leak is not severe.
5. The Oz's (lbs/weight) of 134a/12 for motorhome Dash AC systems is determined for the specific chassis and includes the length of any hoses used on that chassis. Doug

[azpete]

as teachers pet noted, his unit had a 30 foot line in the system. there is the main problem with using weights for recharging motorhome systems. the hoses are added by the manufacturers, and some have no idea how long they are. and they vary from model to model. so weight numbers supplied are a hit or miss situation.
if you have partial cooling, there is a 95% chance of no leak. just add some freon with a dye and check it with a uv light days later.
if there is a leak, repair it, evacuate the system, and recharge it, using the pressures as a guide. you can get a vacuum and the guages,at autozone on loan.
when the pressures are near what they should be, check the sight gauge if present. keep adding till it clears up, or the a/c cools to suit you.
i know this is a backyard mechanics approach, but is works for me, and i have used it with much success on all my coaches. just dont over do it with the freon. moderation in all things.
having said all this, most of you know that the dash air does a poor job of coolng the whole coach.
i use the generator and run the basement air on my meridian dp. it doesnt affect the mileage that much. no more than running the dash air. all of it takes fuel.

[dougrainer]

A/C System Operating Pressures
Ambient Air Temp (F) Entering Condenser Suction Pressure (PSIG) @ Evaporator Outlet Discharge Pressure (PSIG) @ Compressor Outlet
50 5-15 75-125
60 5-15 100-150
70 10-20 125-175
80 10-20 150-225
90 15-25 175-250
100 15-25 200-275
110 15-30 225-325
Doug

[dougrainer]

APRSRVer wrote:
Most times there is a sight glass in the liquid line. It should be clear. Clear would mean it's fully charged and all liquid is passing by or that is completely empty. If you see bubbles, it may need more Freon especially if it is nearly all bubbles. If only a few bubbles, the system probably has enough.

134a systems will NEVER have a clear sight glass. Freon 12 systems will. Doug

[rgatijnet1]

If your dash air is still putting out cool air, meaning that the system is still intact, just low on freon, I would buy one of the recharge kits at an auto supply house and charge it yourself. The kits come with instructions and usually include a gauge that gives you a green area that indicates when the charge is sufficient.
If you take it to a shop, they will probably say that you have a leak, which you obviously do have, and they will start listing all of the laws/rules, that they claim will not allow them to recharge your system without first repairing the leak. The facts are that 99.9% of all AC systems will eventually lose some small amount of freon through the years. The simple addition of a can of freon may be sufficient for several years of good AC service.
If your system does not have any freon at all,and only puts out warm air, then by all means take it to a shop, have the leak repaired, the system evacuated, and properly charged.

[wa8yxm]

Alas, the proper pressure varies with conditions and make and model. The service manual for your rig will show the proper pressures for the current conditions. Any answer I can give would be "Generic" and most likely wrong.

[Teacher_s_Pet]

Lost our dash air when coming out of Texas this spring, had it checked out in Elkhart, IN, on our arrival. Turns out it was a 30' plus AC line, running from the engine forward, that had "rubbed through" on the frame, after 8 years of service. The AC tech put in a 6" piece of line, 2 couplings & charged the system. Net result for us was cold, cold air and $168 for him.

[Vet_Man]

Go to a department store, buy a can of ref. 134 costs about $40. Follow the directions on the can closely, the ambient temp is adjustable on the can and also gives the high and low press. Add to the low side of the compressor, it will have an L on the cap that you will need to remove and will be the larger of the 2 lines. It will not fit on the wrong line, it just snaps on. Takes about 5 mins to recharge the system, on need to evac the system. Even I did it no problems., cold now.