RLXXI

If it were my 2 year old truck with a problem it would be the absolute 1st thing I would do but I also have all the equipment in my garage to do so.

Really need to hook a set of gauges up and do a performance test just to be sure there are no blockages etc.

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Crab Balls

So, you're saying we can't rely on Ford's quality control? But, yes I agree it is good practice to eliminate that variable. Not sure many shops do this regularly without good reason.

RLXXI

The ones that built our trucks are just as human as you or I. Mistakes happen and when you have to do something while in motion the odds go up for failure. Then there is equipment failure on some scale, so many factors and things that can and will go wrong ask (Murphy)

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All Hat No Cattle

Please, I'm not trying to barge into a spirited discussion, , but maybe trying to interject some real world suggestions.

The label on my 2010 hood says the R-134 charge is 24 ounces. Not 22 oz., not 25 oz., but 24 oz.

Any manufacturer assumes that you are working with a factory clean system that leaked a little refrigerant, so they put out a pressure/temperature graph that says to put in R-134 until the pressures meet the chart. On a factory-perfect system.

On an 8 year old truck, with an unknown history, the only sure way to know how much is in there is to recover (pump out) the freon, clean it up, and put it back to the proper specs, adding some as necessary. That handles the vacuuming, and brings the level to factory specs.

If you have to do that every couple of years or less, you have a problem.

Not saying that you can't just throw some in and watch your gauges, which I've done, just saying what you have to do to be sure.

wolfy53

This is exactly it! So glad to have a AC guy here on the forum! I am sure you have seen many times where people have just thrown in a can of that 134a and caused big big problems.

I have heard that if the system is low on 134a that it can't carry the compressor oil through it as well. Is there any truth to that? Just curious

As stated I am not an AC guy. I am however a mechanical engineer for the last decade or so. And to do this the right way I know you must evacuate the system! Hold the vacuum and evaluate from their. If the leaks are outside of the acceptable range then you have a problem. Then you must refill with the proper level as well as oil.

I understand your reasoning. But my "leak" is within the acceptable rate. I know this because I had it properly evacuated and a vacuum held. But you are right if I have a true leak I could have much larger problems with my system.

However you are making a lot of assumptions about the system. By just putting in the 134a yourself you are assuming you don't have a leak. You are assuming that you don't have any moisture and or other gases such as air in your system. You are assuming you have the right amount of oil still in the system. And most importantly without a proper set of manifold gauges you are assuming that the little gauge on the can of 134a is giving you the right information, which it isn't. Thus you are assuming you are putting in the right amount of 134a, which you really have no idea.

I bought my truck 1.5 years ago it was already 6.5 yrs old with 98k miles on it. I have no true idea how it was taken care off. If say someone hit a rock and took out the condenser and then just replaced it and "filled" it up with a can of that 134a at walmart. And just a little gauge on that can of stuff you buy at walmart is not providing you the proper information.

This is exactly it as well. Very well put! You can do a lot of damage to the system by overcharging the system. Also with those cans you don't have compressor oil!

Just to clarify, my system was "working" as even when the heat index was over 110F and temp was 100F it would keep my cabin very comfortable even on fan speed 3 of 4. It was not however working at top efficiency. My mechanic did the evacuate and recharge basically because I asked him to As I bought the truck used. Now I know what is in the system. Also this cost me $105 bucks. So not much more then a simple can of 134a, sorry I can't remember the name it. I know R12 was freon...

RLXXI

e

Typically a normal mobile a/c compressor has about 6oz of oil in it, then 2 ounces for the evaporator, 2oz for the condenser, and 2oz for the accumulator. Refrigerant and oil transfer at different rates depending on which side of the system, high/low but the Freon and oil are indeed mixed as the system operates.
You can have the right amount of refrigerant but not enough oil and the system will not perform properly.
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Crab Balls

Sorry, but "acceptable rate" is something I find amusing when I hear somebody say that, as there really isn't such a thing. You might want to talk to the tech that did the work and ask him how many microns he vacuumed the system down to. If he looks at you funny and starts scratching his *** you got your answer.

You still might have a substantial leak and won't find out for several months.


I've learned to never assume anything. I've been doing this for more years than I would like to mention, working on commercial units that can hold up to 120 pounds of freon so I don't casually hook up the recovery machine to pull out the freon because it is fun to do. Got the gauges and all the equipment to get the job done. Before I evacuate a system I make damn sure I need to. There's the usual visual checks, temperature and pressure readings and a little bit of math mixed in to see what I need to do. Other factors come into play as well.

Of course, auto A/C is another animal. As you mention, too many people do crap they shouldn't do. I'm just saying, a lot of stuff gets done unnecessarily because people either don't have the equipment or knowledge to use it. As said earlier, it is good practice to get a system evacuated if you aren't sure of its history or are sure how to determine if it needs it or not.

That said, would your tech, assuming he knew what he was doing, deliver the same results without evacuating the system? I say he probably would have going by the info you stated. But,since your only dealing with a couple pounds of freon it is easier to hook up the machine and pull it all out. Beats the hell out of thinking and you get to sell some freon too.

RLXXI

An automotive refrigerant system is not sealed like a stationary, be it home or commercial, that compressor front seal has have, is designed to, and will continue to seep a certain amount per year for what the engineers call acceptable lubrication for said seal.

Ask an automotive a/c tech how many microns he vacuumed the system to and your likely to get looked at like your some sort of idiot because we measure it in Hg" most good vacuum pumps such as the one I have will pull close to 30" Hg.

I get where your thinking is coming from but you are trying to compare oranges and grapefruit, they are both citrus and both have a rind but that's where the similarity stops.

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wolfy53

Both great points fellas. Remember Crab I took my truck to him My system by most standards was working just fine. Even on 110+ days it would keep my truck more then comfortable without having the fan on high. I just felt it could be better. And doing my research I found that automotive AC "leak" And I do have the results to show that "whatever" he did my system performs better. No I don't have any thermostat readings or anything like that but I do know that when the heat index was over 115 after my AC fix it worked much better, as I had to turn down the fan to speed 2 of 4. My wife even noticed and asked what I did. I trust the guy as he's an independent shop owner that has been in business for 20+ years.

Did he have to evacuate my system... No. He could have just topped off the 134a. But that in my opinion is not the correct way to do this. It is a short cut and a half way job. Would it of worked probably. But I don't know what else is in my system. Like our other car that I bought new I know its history, not so with my truck.

As you said you have seen people just throw stuff in their systems. I don't have the proper equipment to do this. I know I don't know what I am doing with these systems. I do however know the theory and how they work and why. I know enough to know I'm not an expert. So I turn to the experts. And at a price that was $35 more then just a can of 134a, it's a no brainer! Get it done right

I can understand not evacuating out 120lbs of freon! In those situations it makes sense to dig into the issue much more. For my trucks lil ac, naw.

wolfy53

Just to update. Trucks ac is awesome. My buddy borrowed my truck yesterday and said man your ac is cold! Good to have another opinion.

Wish I would have taken thermo readings before and after now...