A/C question

It sure sounds like it works for a few of use and I personally have never had a problem and have always had cold air when it hits 120 F outside.

ollier wrote:

Reply to
user
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Not hardly. That was in jest, guess you didn't see the gbfg

Hmmm.. wonder where you live that all these self taught folks have all this expertise. Also wonder on who's equipment they screwed until they got it right.

Reply to
Roy

its clicking on and off on the low pressure switch.

Reply to
Nathan W. Collier

as previously stated, you need to pull a vacuum to at least 500 microns in order to properly evacuate the system of moisture and non-condensables.

done it _many_ times with any type of compressor you can name. having used a micron gauge on it i can tell you with authority that youll never achieve

25% of your target 500 microns.

it depends upon what you mean by "really failed". a minor leak is nothing. most of the charging products contain leak stopper and ive found it very effective in the past (if its a seal issue).

Reply to
Nathan W. Collier

Because the fluid in my pump is getting old and is about due for a change. Do you know of any retail places here in NC in the Raleigh area.

Reply to
TBone

you dont change it after each use, or its just been sitting or what?

i would recommend johnstones, although they may require you have an account with them.

Reply to
Nathan W. Collier

This is an industrial vacuum pump and nowhere does it say to change the oil after each use. Probably because it was not built for the sole purpose of air conditioning service. Actually, it used to live at Bendix with about 5 of its brothers running 24/7 to test flight control systems.

Ok, I will check that out.

Reply to
TBone

if they tell you that you need an account, use mine.

Reply to
Nathan W. Collier

You mean your bank account :))), I could use some Dale

Reply to
Dale Yonz

I just did a compressor change out on an 1989 F-250. I used a commercial vacuum pump that pulled a vacuum of around 27. What I want to comment on is that my FORD service manual states pull a vacuum of at least 25 for a max of 30 minutes if the whole system had been replaced. Now 25 is not that great of vacuum and far less than someone on this group has been saying is required. So far I did everything that the FORD manual stated and everything seems to be working OK. What I also found interesting is that the FORD manual said after you disconnect the vacuum pump make sure that the system will hold that vacuum for at least 5 minutes. Now I do have a problem with this statement. I would probably be bringing the new compressor back for a refund it is only held a vacuum for 5 minutes.

Ron

TB>

Reply to
Ron

you pulled 25Hg. thats not the same thing as 500 microns.

youre reading it wrong. it means to wait at least 5 minutes to make sure it holds the vacuum. if it will hold vacuum for 5 minutes it will hold vacuum indefinately.

Reply to
Nathan W. Collier

It states (the FORD service manual) at least 25 inches of Mercury and as close to 30 that you came get. You are right that is not the same as 500 microns. So how does microns relate to inches of mercury ?

So what is so magical about 5 minutes why not 2 minutes or 10 minutes or

24 hours ? I help a vacuum over night on the last job with no problem but the compressor seals would not work in reverse so the vacuum test was basically worthless as far as telling me the seals were good ?

Nathan W. Collier wrote:

Reply to
Ron

Reply to
Steve Scott

Micron is really almost a useless measurement to almost anyone that is reading this newsgroup. It cannot be measured with the equipment available to the service or home repair person. Vacuum pumps are specified in volume/sec and inches of mercury. Volume is not important to us because we are working in a closed system if we had a hole in one end and were trying to keep a vacuum inside then volume per minutes would be very important now I sure hope everyone knows that you must have your AC system closed before you start drawing your vacuum. So now all we need to do is determine what the min vacuum we need to pull and from what I understand now about this subject almost anything that will draw a vacuum will work just fine on our AC systems if it can acheive a certain ?? inches of Mercury. So now lets get off this micron issue and on to something that we all can measure. If a manufacture of a specific vacuum pump states it can draw 50 micron then at what inches of mercury are they talking because then any vacuum pump that can achieve that pull will do that same thing, volume again is not important.

Thank you, Ron in Phx, AZ where AC is required.

Ron wrote:

Reply to
Ron

Micrometers... 1 millionth of an inch. 1" of Hg = 25,400 microns of Hg. However, the scale is inverted. In other words, a perfect vacuum (29.921" of Hg at sea level) is 0 microns. Therefore, 500 microns is about 29.903" of Hg.

Reply to
Tom Lawrence

microns are smaller incriments of measure and are much more "sensitive" and accurate than Hg.

its just a guestimate. i typically do something else for 15 minutes and check back.

if thats the case you should charge the system with nitrogen and make sure it maintains pressure.

Reply to
Nathan W. Collier

.....if you dont care about doing the job properly that is.

?? i paid less for my micron gauge than i paid for my pressure gauges.

if it can pull 500 microns it will work just fine in your a/c systems. if it wont (and it wont) its _not_ "ok" to use it. sure it will make the system run and cool but it will NOT cool as efficiently as it would if it were done right. the suggestion that it will is irresponsible at best.

Reply to
Nathan W. Collier

No, any self respecting residential service tech has a micron gauge. I don't have a clue how often they're used in automotive AC but I suspect not often.

A micron is 0.001mm. There are about 25400 microns to an inch. A gauge set simply doesn't have the resolution to measure a 500 micron vacuum.

BTW, a perfect vacuum would be 0 microns. 500 microns is 0.5mm.

Reply to
Steve Scott

will someone please answer the question that was asked a couple posts ago:

what does '500 microns' equal in inches of mercury ?

Reply to
TranSurgeon

I thought I did... 29.903"

Reply to
Tom Lawrence

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