90 Ls400 Ac Out

[Novacaine]

Hi all I am new here so don't flame me too much

I tried the search but it wasn't cooperating at the moment so here goes

my AC stop blowing cold a couple years ago for my parents and the dealership told them it would be 2 grand to fix which they weren't about to pay for AC. This was mainly due to their need to convert it to r134a cause they wouldn't recharge the r12. I am now looking to fix it up for them cause the humid summer are just plain nasty in that car that sits outside to bake with its black paint. Now I know there is no reason it should cost 2 grand when all it needs is a flush and to replace the oil in the condensor and maybe the dryer?. I was wonder how hard this is to do and the cost, or if any one knows a reputable place in New Jersey to get this fix where I won't have to sell my organs to pay for it. Other option would be a replacement for r12 that is just a flush and drop in no prob. I have heard of people putting in r134a straight in but in a lesser amount to make up for the increased pressure. They said it worked just fine but that was in an 1990 mazda RX-7. It has been without AC for a while does that mean it needs new o-rings and hoses and crap too?

Sorry for the really long post and if some knowledgable people acctually read this thank you. The car is basically mint except for stupid LCDs alread read about that and the AC. so I am looking for people that have done this or know exactly what needs to be done.

[Novacaine]

cmon, I just want to know what is invloved in a conversion to r134a from r12. What needs to be done because there is a lot of misinformation about what a car really needs for this process.

[Rich Sweitzer]

No flaming, just my best shot at some practical information . . . but I have to say that I’m not an AC technician, just someone that’s had a few AC failures in my own vehicles.

First off there should be no need to convert the system to R134a. R12 is still available and still legal to use. (albeit mighty expensive, about $40/pound and, as the system is designed for R12 it will probably work better with it). Only the manufacture of R12 has been banned. (My ‘91 LS-400 requires about 2.1 pounds of R-12.) If someone told you it had to be converted to R134a they were trying to burn you for the cost of the conversion. And by the way, I believe that the LS-400’s AC system’s seals and “O” rings are already compatible with R134a and the associated lubricants (Viton being the material that has the bad reaction and I don’t believe that Toyota used seals/”O” rings of that material on the Lexus.)

R134a is not compatible with the lubricant typically used in R12 systems (mineral oil) in that R134a can't (due to its physical characteristics) move the mineral oil around the system well enough to provide adequate lubrication for the compressor (the only part in the system that needs constant lubrication). From what I've read, the chemical compatibility issue first feared with R12 - R134a conversions appears to be largely unfounded. In fact, it is now believed that if you remove at least 1/2 of the mineral oil and replace it with a compatible synthetic lubricant (PAG, Ester, ROC) you can achieve a satisfactory conversion, if you were so inclined.

There are functional "drop in" replacements for R12 available, all of which have issues (the EPA DOES encourage the development of drop ins, by the way). Most are either blends of R22 or R134 and some other "approved" ingredients or they are hydrocarbon based (ie. R290, propane). All are reported to work quite well, or rather poorly, depending on individual circumstance and who is doing the reporting. All but the hydrocarbons require the same license as R12 for purchase (R134a being the only other that does not require licensing so far as I’m aware). The hydrocarbon-based refrigerants are apparently not "street legal" as per EPA regulations and some of the individual states but there is some contention about that among the different parties involved. But if you only need a tad over two pounds of R12, why convert? (A friend of mine just had the AC system repaired and recharged with R12 on his Pantera and the total cost was around $400.)

You question the need to flush the system and replace the oil. There are a variety of things that can cause AC system failure but spontaneous system contamination (the usual reason for a flush) generally isn’t one of them. Unless a destructive compressor lockup has occurred (pretty rare in an LS-400 with its sophisticated compressor monitoring I would guess), or the system has been opened to the environment (moisture contamination) chances are the oil is just fine (I would replace it anyway if the system has been dormant for a while due to loss of refrigerant and/or has to be opened for repairs). The ECU for the AC system in the LS-400 can yield some very useful information about the system. Normally you can put the unit into diagnostic mode but your LCD display is dead so you won’t be able to read the information it’s trying to tell you. Your best bet at this point is to have the problem evaluated by a reputable and trustworthy automotive AC shop. Something to consider in keeping the repair costs down is to look for a shop that will use aftermarket parts rather than genuine Toyota material. (Yeah, I know; I’ve offended some folks by that statement but when I did my timing belt I used idler bearings from the local bearing supply house for about 1/3 the price and guess what . . . they were the EXACT same KOYO bearings that Toyota installed on the engine at the factory! Go figure . . .)

On my ’91 LS-400 the AC stopped working at the beginning of the summer. Green AC light was on like everything was OK but the compressor would not engage. It turned out the refrigerant had leaked out and the low-pressure interlock kept the compressor clutch from engaging. Found the leak at the manifold on the compressor. After replacing the manifold gasket and the receiver/dryer (a must if you open the system or it’s been at low pressure due to a leak), evacuating the system and recharging all was OK again. Cost of the gasket, less than $10. (I suspect that most shops would have charged for a rebuilt compressor).

Good luck with this. I suspect that you can get the system back up and running for quite a bit less than the 2k that the dealership wanted for the repair.

[Rich Sweitzer]

Oh, one other thought. I wouldn’t try to do a conversion to R134a using one of the aftermarket kits available at the local auto parts store. To do a conversion you first need to repair any leaks in the system, regardless of the refrigerant used. These kits don’t provide a means to detect a leak.

These kits also include new oil, either PAG or Ester. Both are very hygroscopic (they absorb water) so they need to be installed very quickly and the system sealed immediately (with a new receiver/dryer). (Both these oil types are major skin irritants, you need PVC gloves to handle them, and don’t breathe the vapors either.) Then a vacuum has to “be pulled” on the system for about an hour. If this step isn’t followed the system will have both air and moisture in it. The air will cause the system to perform even more poorly that it would with proper installation and the moisture will react with the other chemicals in the system to form an acid that will lead to very premature system failure (compressor lock-up, condenser rupture, expansion valve failure). If there is enough moisture in the system it can even cause freeze up of the expansion valve or worse.

If you want to learn more about R12 to R134a conversion Haynes has a good manual on the subject for under $20.

[Novacaine]

thank you, you are the man. I am not sure if there is a leak or not because the dealer refused to recharge the system and said they needed to convert it over to r134a and all that jazz. My famliy knows a reputable mechanic who said he'd have his friend look at it and more than likely cost a lot less to fix, but I just wanted to know what was involved so I could know if I was getting ripped off or not. Well thank you for your detailed response