Freon leaking in chassis AC

My daily driver is 14 years old but looks like new and only has 90k miles. I also have a very small leak that requires charging every year. No big deal to me to do so.

A freind fought something like this for along time with his Suburban. It turned out there was a screw poking a long metal line inside the vehicle.

I don't buy the tech's explanation at all. But these automotive systems do leak a certain amount of refrigerant per year. No seal or hose connection, or even the hose material for that matter seals perfectly. This can be as much as 25 grams of refrigerant per year! So if it's an older system (you don't tell us what it is) it could just need a recharge. What is the year and make of your chassis?

tompla wrote:
I am having to recharge my chassis AC every year. My class A MH has been checked for leaks using the dye/black light method and the "sniffing method". No leaks were found. WE live in a cold winter climate. The technician tells me that the leak is very slow and will be very hard to detect. He believes that temperature of the Freon determines when the system will leak. When the Freon is warm, it maintains pressure in the system. There is some type of little valve that seals the line at some place in the system due to the maintained pressure. When the Freon is cold due to winter storage in an unheated shed, it does not maintain pressure and hence the little valve does not seal tight and the system leaks. Have any of you heard of this? The tech feels it is better to spend $50+ to recharge each year than go any further in solving the issue. What the thoughts of you who have experienced this.

How old is the system? I'm assuming you have an R-134 system. (1995 and later) R-134 is a smaller molecule than the older R-12 refrigerant. It can seep out through O rings that have gotten dry or just shrunk from age. I've also seen it seep from the seals on a compressor as well as the low pressure switch assembly. $50 doesn't sound too bad as a grenade (12 oz can) of R-134 can run a good $15-20. You will probably spend several hundred dollars fixing the leak and even then you may not find that one little O ring that's seeping.

All refrigerants have a very defined pressure to temperature ratio as long as there is liquid in the system. At a given temperature (when not operating) there is a given saturation pressure. In the summer with the warmer temperatures the pressure will be higher. In the winter with lower temperatures, the pressure is lower.

A leak is nothing more than an orifice and at a higher pressure behind the refrigerant, the leak rate is higher. Lower pressure, the leak rate is lower.

Now back to finding the leak, the tech that told you about a "little valve that seals", you need to find a better refrigeration technician. There is not one thing on the system that is supposed to leak. The whole idea of a A/C system is to keep the refrigerant in the pipes and hoses.

If the tech uses the right equipment he can find a leak that is low as a couple of ounces a year. He probably does not have the equipment or does not know how to use it and look for a leak... again, time to find a new tech.

Refrigeration engineer and service since 1970 and I have found my share of leaks. Also see more than my share of poor technicians.

Ken

Freon is like a fart in church. It can be hard to keep in. Look for an oil stain anywhere. Freon is heavier than air and when sniffing, it's best to check under things. If the leak is in the evaporator, hidden in the dash it's difficult tp pin point it to that but sniff the vents and lower outlets. Doesn't seem that it's a bad enough leak to warrant spending a lot of money on.

Tompla, you don't say if that $50 includes any leak stop product. If you're having it done, I strongly suspect the answer is no.

IMHO you should add a can of leak stop first, then if required top up the system with straight 134A.

In northern climates if the unit is parked all winter the shrinkage of various components seems to aggravate the leaks.

JaxDad wrote:
Tompla, you don't say if that $50 includes any leak stop product. If you're having it done, I strongly suspect the answer is no.

IMHO you should add a can of leak stop first, then if required top up the system with straight 134A.

In northern climates if the unit is parked all winter the shrinkage of various components seems to aggravate the leaks.

I know nothing about leak stop for AC units but I know from experience how bad leak stop is for radiators and power steering pump