A/C seized up

[kenw]

I'ver converted several cars and the only part to be changed was the accumulator/dryer.

Changing the orfice is usually claimed to be needed, but again I've never done it nor have I known anyone who HAS done it. Theoretically, if you do not change it, the capacity of the system (cooling-wise) will drop about 5-10%. In my book it isn't worth hassling with as most cars have cooling capacities larger than many houses.

Do not leave ANY old oil in the system as the old r12 oil is NOT compatible with r134a and will not dissolve, reamining liquid and "slugging" the compressor, a life-shortening thing for sure. You MUST evacuate the system completely, and a couple of partial refills and evacuations at ever-higher vaccuum levels is the best way to insure good results.

Oring changing is not necessary on most cars, they are compatible with both types and have been for many years. Again, I've never changed them (altho the new accumulator came with new o-rings, which I of course used.)

Most cars already have a high pressure cutoff switch, it is often built into the compressor or the output (small) tube. You will often have a low pressure cutoff, located on the inlet (large) tube).

 

[Gary Allan]

quote:

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The R-12 dessicant won't work with R-134a.

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This is something I always found interesting. In my auto AC class we had a R/D cut in half to show the internals. In the 60-70s it had nothing more than a bag of the purple tinted dessicant that I've seen everywhere else in my lifetime experience (some of the labs that I've worked with). My lab at work had a large glass container of the stuff (looked the same) and they used it to extract moisture from other substances. The regenerated it by putting it in the oven and heating it to release the moisture. In the confines of the AC system, vac'ing the system should purge the dessicant of moisture (vac dried).

What I can't seem to settle in my head is how moisture (suspended or condensed H20) is somehow magically altered in the presence of R-134a, requiring a different dessicant. This just hasn't been adaquately explained to me. In the absense of an authoritative reason ...I would tend to think that this is something generated by the reciever/dryer manufacturers to "tag along" on the retro fits as a "must do" type thing ...along the lines of swapping out your brake fluid on a bi-annual basis(wink-wink)

 

[brianl703]

I have R134a in my 1988 Mustang with the original accumulator. It's been like that for 3 years and 40,000 miles now, and no problems.

 

[tdi-rick]

Gary Allen, I'm with you on the drier front.

They use exactly the same desiccants between a CFC and HFC drier, a mix of activated alumina and molecular sieve.
The more modern driers possibly use a few more proprietary additives for acid control, that is all.
Some commercial/industrial manufacturers, such as Copeland, specify certain moisture holding capacities for their driers when using the modern refrigerants. Again this is for acid formation control.

BTW, that desiccant you saw back in the 60's was silica gel.

I have similar feelings to Chris142 re rebuilt refrig/air con parts. I just refuse to use them in my business as well (domestic/commercial/industrial refrig/air con) except on large semi-hermetic and open drive units, having been stung years ago with substandard re-builds.

 

[kenw]

replacing the dryer is usually easier/faster (ie, cheaper) than to super-dry one. The rule we used was anytime the system is open to the air, it got a new drier. Some of this was preventive simply to replace existing used dessicant. Granted this was industrial units, but the theory is the same.

When converting, the dryer is a tough thing to remove oil from, so replacing the dryer also helps rid the system of old insoluble oil.

 

[tdi-rick]

quote:

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In the confines of the AC system, vac'ing the system should purge the dessicant of moisture (vac dried).

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I missed this part of Gary's post. Kenw's reply is very good.
The old silica gel was easily rehabilatated by de-hydrating, the modern stuff less so.
You'll also find with the modern dessicants that they need considerably more heat than just reducing the boiling point in a good vacuum will provide to release their moisture.

 

[Gary Allan]

Lotsa good stuff here. As you can tell, I've bypass a few evolutions on AC. My Caravan luckily has a pilot valve having missed the evolution (it was one of the last R-12 systems) of the cheapness of the orifice tube.

It's like many things that we had a very good grip on at one time ...step out for 20 years and a new set of paradigms are formed and you just look at the intermediate terrain and scoff at it.

We see many evolutions of "preferred" practices that are about a 30/70% split between fact and mere market movements ...where the actual parts suppliers and the vendor have higher throughput ..but the bottom line to the vendor is about the same. Sorta like the mechanic who rebuilds a starter drive instead of throwing in a rebuilt unit. The mechanic, by throwing in the rebuilt unit helps the parts man more than he does his labor bottom line in the action. The customer pays the freight either way. We then see the next evolution where, since nobody bother to rebuild starters at the mechanic level...that quality starter parts are in limited supply to anyone but the rebuilder trade. Then the price of the inferior starter parts gets jacked due to real estate costs on the shelves. Hence the new "must do" is to throw in a reman.

Essentially I'm saying that there is a fine balance between "proper" and necessary ..and many of the practices that are "must do's" are very much a "cultivation" and evolution of the market more than they are required actions.

For example ..many here have routinely replace the receiver dryers for so long ...that they would never consider doing anything else ..yet I doubt the failure rate of retaining the old receiver dryer has ever gone more than one or two failures to test the alternative practice ...even if they only represented 1% of failures. Now a few more $$$$ are added to the basline costs of a retro fit merely for the sake of "doing it right the first time". Add 5 -10 years ..industry sponsored clinics and curriculums...and the thought on not doing it is heresy.

That's how you cultivate a market.

 

[Gary Allan]

I'm not arguing with you per se' ..but this evolution is more a function of decreasing manufacturing costs and higher labor rates ..much like repairing toasters. It's just not done anymore. I learned how to use a "grower" (spl?) tester ..cut commutators ...replace brushes ..drives ..etc. That was a skill at that "state of the art".

In the example of the replacement of the receiver/dryer situation, the cost to the consumer is higher ..and the practician doesn't pay for it. The customer is prepaying an insurance policy for the job to the main benefit of the technician.

If you came into the trade at a certain point ..I doubt that there would be enough statistical evidence in anyone's memory (the instructor or the technician) to say "Oh ..I tried that ...and got really burnt". It eventually becomes "just the wya you do things".


Again, I'm not saying that this is an "unwise" move or policy ...it just adds another mandatory cost to the job that I doubt too many, at this point in the art, question the necessity of it ..with or without bona fide evidence ...it is just "accepted" as an absolute truth.

It falls along the lines of doing wires, cap, plugs, and rotor all at the same time ...except MUCH more expensive.

 

[kenw]

I understand your point and guess we agree for the most part.

First learned of some of this when I had a CV replaced on a car. Mechanic offered to either:
1) press a new CV onto my axle
2) buy a new axle with CV already installed

"So what's it mean to me?" I asked.

"The end price to you is the same because the parts go up a lot but my labor drops; I give you a 90 day warranty on the labor, including the pressing of the bearing, but the new axle with CV comes with a 1 year warranty. Besides, I can use my mechanic for a lot of other things in the time it takes to press a CV off and on. I gotta use my higher $$ guy to do things like press a bearing, another guy can handle replacing the axle in the car. It's not like we are looking for work...

And I can get the axle with CV today because they are stocked locally, the bearing has to come from BFE and will take 3 days to get here...."

So yes, it had by then become accepted practice. But in a society that has so much specialized and very technical labor, this is a logical result and not always bad.

Of course, this is coming from one who HAS fixed a $10 toaster by spending 4 hours working on it....it's the thrill of the fix for me!

 

[Gary Allan]

I wanted to add that in industrial enviroments ..cost usually isn't a factor. There are many instances where an installation is performed by outside contractors at a tremendous premium as opposed to inhouse maintenance. This is the situation where a $200,000 installation costs $600,000 via the outside mechanical contractor. The sensibilty in this is that the process that they are installing represents $500,000/month in revenue and every day that it is not installed costs more money than the savings could ever compete with.

It's the same with the repair of any industrial utility component (compressors, blower, chillers, ice machines, etc.). Down time is far more costly than comprehensive repairs/replacement.

 

[kenw]

"The mechanic, by throwing in the rebuilt unit helps the parts man more than he does his labor bottom line in the action. The customer pays the freight either way."

actually, i prefer to use remanufactured parts, as does my mechanic. His reasons, which I agree with, are:

the reman part will be of more consistent quality due to the factory controls. This of course assumes a quality shop did the reman job. As a Manufacturing Engineer, factory jobs are almost always more consistent, again assuming a quality factory...The guys in the factory spend all day rebuilding the same thing. They will have a skill depth far beyond that of the guy who rebuilds one per year.

The reman parts usually have longer warranty. This is a plus for the customer certainly, but is a huge overhead reduction for the shop. Most would rather save the overhead costs of providing additional warranty and sorting out external material -vs- internal labor defects. Was it my labor that screwed it up or the bad material I bought? And then you have to convince the material provider, return parts to several suppliers....It's not worth the hassle to the average shop owner.

Using reman parts can acutally be more profitable since they allow more volume of customer billable labor. The time spent rebuilding can be spent replacing parts at a higher per hour rate, or at least a higher thruput rate. Many bookrates don't include a rebuilding factor, they are simply a parts swap rate.

 

[Chris142]

There's a big difference between installing a rebuilt axle and installing rebuilt A/C parts.
Most rebuilt axles cost less than $100 and take less than 1/2 hour to install.

I've never seen (not that it doesn't happen) a rebuilt axle cause damage if it goes bad. It may click or the boot may tear but it usually is confined to the axle itself.

Lets say aa rebuilt axle failed. I lost 1/2 hour of labor.....No big deal and the axle was under warranty so I get a replacement.

Not so with A/C parts. If a rebuilt compressor dies it will usually contaminate everything. Sometimes even the evaporator. Most evaporators are in the dash and may take many hours of labor to replace.

So say a rebuilt compressor fails and it's under warranty. Ok I get another one.

What about the condensor?

I eat that--$150 + labor.
Replace the compressor, lets say that it's a Caddy---3 hours labor @ $75 hour. I do for free.

$25 worth of flush solvent through the lines.

The evap must be replaced as it's too contaminated to be used.

My cost for the evap is $400

12 hours labor to install it!

Naw Theres no reason to install a rebuilt compressor to save the customer $100.

I just lost my *** on this job.

Now ya'll can see why sometimes it's better to install a new part instead of a rebuilt.

Axles= Go rebuilt.

A/C stuff= new.