The cooling power of my a/c has deteriorated over the years. Two years ago, I had the R134 refilled at a shop. It worked great again that summer, and the next. This summer, it has deteriorated again. I took it to a shop and they said the system has a slow leak and I need the hoses replaced. Total cost was around $450. No thanks.

I recharged/refilled the R134 and it works great again. However, I used all three cans of R134 plus the one can of oil. I'm afraid I might have overfilled it. The a/c seems to work well. I haven't noticed anything wrong.

What happens if there's too much R134 in the system? Is it like overinflating a tire where it's ok until it explodes? Or is it like overloading a truck where engine/drivetrain is overworked?

PS. The only pressure gauge I have is the one for the tire pressure.

 

Typically they will show how much needs to be in it on a sticker on the evaporator. I'll assume you have a retrofit. Then with R-134a you will want to use 85% of this number. So, if it said 2&1/2 lbs of R-12, you'd have 40 oz of R-12. This would mean 34 oz of R-134a.

I dont know how much yours holds, but I've seen some that only take 1&1/2 lbs of R-12, meaning 20.4 oz of R-134a. So with each can at 12 oz, and 3 oz of it with the oil, you added 39 oz. I dont know how much was still in there, either, but if only half of it was gone, you still probably overcharged it.

When you overcharge one, typically something on the high pressure side will pop. This can be a hose, or condensor, both costly items to replace.

Here's what I would do.

1. Take it back to the shop, have 'em evacuate it (take it to 0 psi). Have them credit you for any refrigerant they take out. Also have them remove any oil in the system. Between the refrigerant and the labor you should break even.

2. Go to the parts store, and buy the appropriate amount of R-134a you're gonna need, a can of oil, and a cheap gauge. Tire gauges DO NOT WORK!

3. Charge away, to the correct amount calculated off the sticker on the evaporator.

Have fun!

 

Can you expand on this?

 

There is a "safety valve" that will pop off at 425 - 450 psi I believe.

 

My 1970 F-100 didn't have a safety valve, and I just got done paying $40 for a new hose to be put on the fittings, and some fittings replaced. When that sucker blew, it was instantaneous. No warning at all. Those old hoses are like that I guess.

This spring, I had to replace a condensor on the '92 explorer. I had the system charged correctly with R-134a. The problem with the R-134a retrofits is that they run higher head pressures (high side pressure). This stresses components. They may not fail right away, if at all, but overcharging dramatically increases the pressure and the likelyhood of that happening.

You may be ok with a safety valve, I dont know what vehicle or year it is, or if it even has one.

Good luck!

 

Most R134 systems have a high pressure cutoff switch as well as some R12 systems.

 

High Pressre Cut off switch is stock on stock 134a, but if system was retro fitted by "shade tree" mechanic probably is not installed.

 

The truck in subject... 94 Explorer. It came with an R134 system when we bought it new.

 

It only takes about 1.75 lbs of freon in that system +or- 4 oz, so yes it is overcharged. This will cause excessive head pressures and will eventually blow something, shouldn't be getting even decent suction pressures as the low side is unable to drop enough to cool efficiently or cycle off the A/C. The hotter it gets outside the higher the pressures will get. Since it should have a high pressure cutoff switch it should not allow it to get high enough to blow the popoff. You should have noticed this nearly immediately as the cut switch should cycle off the compressor as the pressures get way up there.

 

If you put an extra can of oil in, that is way too much. Will affect your cooling. Use guages and adjust your freon accordingly. To get rid of the oil you have to dissassemble the system flush it and fill oil from scratch. This is the only way. Your choice on the oil. If it's cool enough for you, live with it. Shoot for around 25 on the low and 190 on the high at 1500 rpm depending on ambient temp.