Adding Freon DIY?

[MSHappyCampers]

Originally Posted by MRUSA14

If is is cold then it is fixed. Don't keep fixing it till it breaks.

Yeah, I know, "if it ain't broke don't fix it!". It just bugs me that the gauge doesn't respond as it should!

[Randy125]

I have to ask, you do have the engine running and the a/c on max cool with max fan when you are servicing the system?

[PushedAround]

Originally Posted by MSHappyCampers

It just bugs me that the gauge doesn't respond as it should!

Read post #41.

[BFlinn181]

Also see post #3 where I cautioned about using full manifold to read low and high pressures. For temperature reading, rather than an infrared I suggest old low tech temperature measurers like this:

1'' Pocket Thermometer

[MSHappyCampers]

Originally Posted by PushedAround

Joe, that is my point from my last post. There probably is nothing wrong with your gauge. The pressure may not get higher as the system is running in equilibrium (the easiest way to explain it) and any more refrigerant will only increase the high side pressure which you do not have the gauge on, not necessarily the low side pressure (where you are charging it from).

Larry, I missed this post. That would certainly explain why the gauge didn't go any higher, but that means the gauge is no working the way the instructions say.

You first rotate a ring on the gauge to set the outside temp. That places a "window" in the green area which is where the needle is supposed to be when fully charged. I'm confused!

[PushedAround]

I can't really answer your question without getting a little technical. When your system is running properly, the low side pressure (or suction pressure, evaporator pressure or back pressure) is in equilibrium between gas and liquid, and the pressure is determined by the temperature of the evaporator (the cooling coils). This relationship can be seen on a Pressure-Temperature chart for that refrigerant. It can also be etched in specific use gauges, like for your auto a/c. That's probably what they are doing with your sliding green window, and compensating a little for the outside temperature.

When your system leaks, eventually the amount of refrigerant will get so low that the equilibrium goes away, there is not enough to have both liquid and gas in the evaporator, and so the pressure will drop, regardless of how warm, the evap is. As you recharge it, the level comes back up and once the relationship is re-established, the pressure is again determined by the temperature of the evap. In fact, as the a/c starts working again and the evap gets colder, the pressure will drop in response to that. This is one of the reasons that you just can't dump some refrigerant in it and "fill it back up" with any certainty unless you have the proper a/c equipment. And it is really easy to overfill it, reducing the performance from optimal until it leaks down to the proper amount.

You would really need both the low side and high side gauges, a good thermometer and a few years of experience to get the charge exactly right just by adding more. In some vehicles they do have what is called a sight-glass on the liquid line which allows you to fill it with refrigerant until the glass clears (stops bubbling) and then you know that you have the proper charge. Most professionals will simply reclaim the refrigerant in your system, and then weigh in the proper charge as per the manufacturer. That is the best way.

[BFlinn181]

I didn't even mention the sight glass, they aren't a good indicator for R-134a, small bubbles can be seen streaming by the sight gauge even when properly charged. They were a better indicator in the R-12 systems.

[Pelledan]

I doubt if the system has a sight glass. If it did, it would probably be closer to the condenser which on MH's is not the easiest location to get to. With one 20 oz can and one 12 oz can in the system that totals 32 oz or about 2 lbs of refrigerant. The old rule of thumb in unit capacity was 2 lbs/ton of cooling. One ton = 12000 BTU's.

You need to locate the lable on the evaporator that lists the system's refrigerant charge. I really don't see it taking much more than another 12 oz can, but over charging can be as bad as under charging. That capacity information is on a label and it needs to be referenced to insure the correct charge is applied.

Dan

[brobox]

Put the gauge in your toll box and enjoy the cold air. Or as Mrac said, keep going until you break it.

[Dtwallace]

Joe & Annette,
I for am so happy you got your system working properly again. You can see there are so many differing opinions on how you should and should not deal with the issues at hand. Part of the confusion is created by your description of the problem and the system you're working with. Since you are not familiar with this type of repair, that's totally understandable. Then you have us guys out there trying to give you the best advice, based on our best an first hand knowledge. Some of us are refrigeration system professionals. I can recognize that from some of the recommendations. Others are not quite at that level but are knowledgeable. We even got into an area that is totally not within the scope of what you needed, azeotropic refrigerant blends. No such thing in automotive applications. Bottom line here is, you got your system up and running by using of the shelf R-134a from the auto parts store. That's totally acceptable given your circumstances. But I must add this, Please do some research on typical automotive A/C system so you'll have the knowledge to properly access future issues that my come your way. Some of the dangers listed by helpers here are real, with and R-12 system, lucky you don't have that, because with the R-134a, you can't high side charge out of the can and kit you purchased, the valves are different sizes. cutting this short now, if it's cold air coming from you system, you are done. No need to add more with out knowing exactly how much charge your system already has in it. Have a great day....