A/C question

OK got that one answered now I would like to see a temperature chart of the center register discharge temperature versus vacuum drawn on your typical fixed orifice tube auto AC system.

From No vacuum pulled in five degree steps to 29.903 which is almost a perfect vacuum.

I personally believe that what you will see is a straight line or two straight lines with anything between these two temps being OK and that vacuum is not related to the temperature output on your typical auto AC at all. The size and condition of the system, the fixed orifice tube and the amount of oil in the system will set the output temp.

Please prove me wrong on this because if a super vacuum will get my AC 20 degrees cooler here in Phx, AZ I am for it.

I did see yesterday that there is a new fixed orifice tube that is really not fixed but variable that is claiming 12 degree better cooling at idle of course I found this after I filled the system with a new charge. If I had a recovery tank I would be installing one of these.

The purpose of drawing a vacuum is to get the moisture out of a system that will cause corrosion and I real believe that is all. Right or Wrong ? I need hard facts or a website that explains this in detail if a vacuum will really drastically improve cooling.

Thanks Ron

tom already did, last night.

if you have moisure or non-condensables in your system it cannot possibly work as efficiently as it would if it were pulled down into a proper vacuum.

nobody said 20 degrees. if you pull a vacuum with a pressure gauge and a refrigerator compressor you might see a difference of 8-10 degrees. if you use a better vacuum source the difference may only be 1-2 degrees...but there will be a difference. we within the industry dont spend $300 for a decent 2 stage vacuum pump for the hell of it. we do it because as professionals we want to give you the best service possible and that means doing it right. if the cheaper alternatives were "ok" we would certainly use them (i got dozens of compressors of all types and size that it ok off jobsites in equipment being replaced) and same some money.

and non-condensables which hinder cooling and can be fatal to compressors and metering devices.

Now that sounds a lot better 1 to 2 degrees is not worth my money as a home repair do it yourself person unless I can find a good suction pump used really cheap. When it 120 ambient and the inside of the car is in the 160 degree range 1 to 2 degrees will not be detected. 10 to

12 maybe but questionable. I have no problem with a professional using the best possible tools if they understand them and aren't just using them for show. I am afraid most do not understand them though and might not even use them most of the time.

I turned my AC on this morning. I installed a new compressor yesterday. The air was so much colder I turned the fan down to low and all of a sudden got smoke that smelled like wood burning coming out of the vents. I thought about it for a while then determined there must be something in the resistors that control the fan that got burned. Sure enough it was packed with leaves. I did get a good look at the evaporator and could see that it was really packed with stuff also so off with the sides to see if I could wash it out. Got the garden hose with a high pressure nosel on it and now it looks like it will pass some air. I have no doubt that it was almost 50 per cent restricted. Just about ready to reassemble and see now much better it will be.

So how do all these other non-condensables get into a closed system ? Moisture I understand and metal parts for things breaking but if the system came from the factory with a good charge and then a seal started to leak I would not expect to have anymore non-condensables in the system after I replace the compressor than before I replaced it other than mybe some moisture from having the system opened.

Back to work (I guess a retired person shouldn't use the word work so back to my fun project)

R>>vacuum is not related to the temperature output on your typical auto AC at >>all.

bear in mind that its also an issue of compressor/metering device damage. it may only shorten component life by a little, but it will shorten component life.

its no longer a closed system once you open it to replace the compressor or other components. you also have component disentigration, minute particles left from machining the new components, etc. where you have moving parts, you have wear.

Now don't confuse Gary with the facts :-)

New question ?

How long is the meant time before failure of your typical auto AC system and what is the normal failure ?

I have 4 vehicles with AC systems that have a combined mileage of around

750,000 miles. I have replaced three compressors. One was an old York piston unit on a 1969 auto that broke a rod at about 200,000 miles. The other two where new style compessors and both were replaced because of seal leaks. The fourth unit is an original York piston unit that is still working great and is 36 years old. I seem to have more problem with seals going bad than compressor blowing apart so I would have to say seal failure is the big failure mode. How off normal am I ? I also never buy spark plugs and find very few bad spark plug wires. I laughed the other day when I was in an AutoZone store and saw a complete wall full of spark plug wires and all I could think about was all the good wires that were being thrown away.

i really dont think there is a realistic way to answer that question. you _should_ be able to expect 10 years of trouble free operation, but ive seen many go much longer, and many only last a couple years. id guess the most common failure is seal failure.

"TBone" are you in michigan? Local bendix plant unloaded a bunch of vac. pumps about 5 years ago.

It depends on the usage of the unit and the climate you live in too. If you live in Teaxs and use it a lot, it will not last as long but I have gotten 200k out of a few compressors and my 89 burb had its compressor replaced at 45k under extended warranty because of quality problems with compressors that year but its replacement is still doing fine 130k miles later.

Nope, from NJ and now in NC. My vacuum pump came from Bendix aerospace in NJ many years ago. My dad worked there and picked it up when they moved the division that used them to PA.