A/C Conversion Help

[The Critic]

Today, I had the A/C system on my dad's 92 Toyota minivan converted from R12 to R134A. I'm not sure if it was done correctly, but here's what my mechanic did.

- Replaced the receiver drier and the o-rings at the receiver drier.

- Flushed the system with A/C solvent and blew it dry with shop air.

- Installed new R134A fittings.

- Did a 15 min vacuum

- Added 4 ounces of Ester oil through the machine's injector. (Toyota recommended amount is 6 ounces)

- Charged with 2.5 lbs of R-134A (Toyota recommended amount for this vehicle when converting to R134A)

The system blows relatively cold, but not as cold as R-12. My mechanic was hesitant to use the full 6 ounces of oil as recommended; he claimed that it might cause the compressor to knock or severely reduce system performance.

The reason why the system was converted to R134A in the first place is because I have a leak somewhere that caused all of the oil to leak out of the rear evaporator. I had the rear evaporator replaced and the system recharged with R12, but it still leaked. That's why I had today's conversion performed. However, after performing the conversion today, we were unable to find any leaks.

So what should I do? Should I go back and have him add more oil into the system? Any idea on the leak?

Thanks!

 

[wirelessF]

How much did it cost? I'm planning to convert to R134a in my 90 4Runner.

 

[The Critic]

Originally Posted By: toytundranator
How much did it cost? I'm planning to convert to R134a in my 90 4Runner.

It was a special deal-- $220 parts and labor.

 

[TooManyWheels]

I can think of no reason to put less than a full charge of replacement oil in a system. I would have a conversation with him about this. If he claims that some of the mineral oil is left, be aware that it doesn't circulate, thus it doesn't contribute to lubrication.

A major oil leak should have left plenty of traces, unless it happens to be in the front evaporator (out of sight). It could also be on the radiator side of the condensor, or on a hidden portion of the line to the rear unit.

Fifteen minutes is not a long time to evacuate, especially if he was using a smallish pump, but you will probably get by with it.

 

[The Critic]

The oil leak was coming from the rear evaporator drain tube. He purchased a new evaporator from the dealer and replaced it, but this only solved the problem temporarily.

We tried to locate the leak today, but nothing could be found.

I'll bring the van by tomorrow morning to have him "inject" more oil.

 

[AzFireGuy79]

I did the same thing on my 91 suburban about 2 years ago. It took about three hours to fully convert. The R-134a does not cool as well as the R-12 being that its less efficient but I lucked out because the condensor on my truck is larger making it more efficient with the R-134a. I have seen quite a few where the condensor size is way wrong and people are always complaining about higher vent temps.

If it was fully flushed I would definately go with the full 6 Oz of oil. I under filled mine initially and decided to go back and fill it to spec. It has worked flawlessly here in AZ now for the past 2 years.

 

[HondaMan]

Mike,

I agree also that 15 min. was too short of a time .... plus how long did he hold vac. afterwards? If it truly has a leak, this would have confirmed.
Finding the leak is another story altogether.

 

[The Critic]

I'm going to drop by tomorrow and talk to him. I'm not sure what he's going to think about all this, but we'll see.

The leak is a bit odd. It can go weeks without leaking, then all of a sudden, I see a huge pool of oil on the garage floor and then the next day, it no longer cools.

 

[SlugGunner]

Originally Posted By: The Critic
I'm going to drop by tomorrow and talk to him. I'm not sure what he's going to think about all this, but we'll see.

The leak is a bit odd. It can go weeks without leaking, then all of a sudden, I see a huge pool of oil on the garage floor and then the next day, it no longer cools.


What main a/c component seems to be located above the area you are finding the oil on the floor? The molecules of R134 are much smaller than the molecules of R12 and can find 'leaks' that didn't exist with the R12. This is why on some older systems it is recommended that the a/c hoses be replaced also, especially if the hoses show any signs of deterioration. I'm wagering that it is the rotational seals on the compressor is where the 'leak' is located.

As far as 'pulling vacuum' on this system, it should be evacuated for a minimum of 20 minutes (30 minutes if the system was 'broken open' and flushed since you'll have more moisture in the system to remove). Then the external valves on the gauges should be CLOSED and the system LEFT UNDER VACUUM for 30 minutes to test for any leaks (also allows drier time to absorb any remaining moisture in system). Freon charge then hooked to gauges and all lines 'purged' so no atmospheric air remains in lines and contain only freon. If oil was added initially, it should be done (added to compressor) prior to closing up the system and 'pulling vacuum' on system. Actual charging procedure of adding freon into system can vary depending on type/brand of system involved and ambient temperature and humidity levels.

BTW:
Pressure levels for R134 are HIGHER than for R12 and gauges calibrated for R134 should be used.

 

[mechtech2]

Vacuum leak down testing does not always show pressure leaks.
Some seals leak with pressure, not vacuum, or visa versa.

You obviously have a leak, so what is the problem determining the next step?

 

[SlugGunner]

Originally Posted By: mechtech2
Vacuum leak down testing does not always show pressure leaks.
Some seals leak with pressure, not vacuum, or visa versa.

You obviously have a leak, so what is the problem determining the next step?


You are entirely correct.... but if it can't sustain the 'leak-down test' for 30 minutes, it definately won't hold 'pressure' during normal operation. There is also a substantial pressure difference between the 'vacuum leak-down' vs. the normal operating pressures, especially on the 'high-pressure side' of the system when using R134.

What methods or 'leak-detecting' equipment have been used so far to determine the source/location of the leak? Was a vacuum 'leak-down test' ever performed BEFORE CHARGING THE SYSTEM? How many times has he 'recharged' the system KNOWING THAT A LEAK EXISTED?

 

[AcuraTech]

Conversion to 134 is a PITA, not only because it never cools as well as 12, but because you're dealing with a system that is over 15 years old and because of that prone to leaks. Add in the major costs associated with conversion, it's really a roll of the dice. Sure, it might work fine, but it also may not.

My car originally came with r-12, I replaced a bunch of o-rings and filled it with r-414b(Hot Shot) last summer. It worked great for awhile, then slowly went back to nothing. My condenser is getting rotten, the compressor seals are leaking slightly, so I'm done. It's windows down for me this summer!

That's good though, because when I'm sweating like a pig this summer, it will inspire me to keep saving for a new(er) car!

 

[Chris142]

When doing a retrofit the standard oil amount is 3.5 oz of oil for every pound of refrigerant used. Since the van used 2.5 lbs of refrigerant it should have gotten roughly 9oz of oil.

What Mr. Critic failed to mention is that the system has a rear unit too. A little bit of extra oil needs to be added because some will tend to stay in the lines that lead to the rear evaporator.

If I had done this retrofit I would have added 10-11oz of oil. Yes too much oil can affect the cooling performance but 10oz when it's split between 2 evaporators, lines etc wont affect the cooling any.

Generally when a system works ok then suddenly goes flat overnight it has a leaky front seal on the compressor. When the system is turned off and the compressor stops spinning it may stop on a spot that lets the refrigerant leak through the seal.

Other times it wont because it stopped in another position.

Critic and I had a short discussion about this job and the fellow that did the work and IMO this guy should not be working on an AC system at all. From what I was told the "mechanic" needs to go back to A/C school or find a new career in fast food.

15 minutes is not nearly enough time to boil any moisture out of a system, especially on a cool day. To remove moisture the system needs to be evacuated for atleast 45 minutes at a temperature greater than 85F. Any temp below 85 and the moisture won't boil.

The "Mechanic" also flushed the system then used moisture contaminated shop air to purge the solvent from the system.

Critics system is doomed. No oil and lots of moisture in the system is not a good thing. If the compressor doesn't grind it's self to death soon the moisture will begin to attack the system from the inside out.

 

[mikey12]

Converting an old R12 system to R134A is expensive if you do it right. All those R12 refrigerant hoses should be changed out, not just the orings. R134A molecules are much smaller than R12's and will leak through the hose linings over time. If you have leaks with R12, you will have more with R134A.

If the compressor has a sump, all oil must be removed. Ester oil is the best oil to use on conversions as PAO will get interesting in a hurry (got milk?). Flushing is good and using shop air is not a problem as long as it is very clean. Moisture will get boiled out under the vacuum. 30 minutes minimum once the gauge needle is pegged.

 

[Nyquist]

I agree. The guy who did it is an idiot and should not be trusted. Those driers can only handle a couple drops of real moisture, and I guarantee that by installing the drier before he "purged" the system with shop air he's exceeded that already. If I were you I would go back to him and say that you want him to pay for a new drier and recharge before your condenser starts sending shavings out into the whole system.

 

[RH+G]

While that was not the ideal way to do a conversion it was better than most shops were doing in the past. ALso make sure u check that lines to the rear evaporator and the condenser. Changing the condenser to a newer style will help bring down the temps

 

[The Critic]

Sorry, I've been busy and haven't had a chance to give an update.

The system was flushed and "blown out" prior to installing the new receiver drier.

I took the van back and he grudgingly agreed to add another 3.5 ounces of oil to the system and recharge it with 2.5 lbs of refrigerant. So at least now, I have the correct amount of oil in there.

Also, the compressor cycles about four times a minute. I don't think it cycled before. My Saturn's compressor never cycles, it just stays running all the time. Any ideas?

Thanks!

 

[hal]

remember that R134a runs at a higher pressure than R12. I've done the conversions before and always put about 1 pound less refrigerant in than it's spec'd for otherwise you could blow a seal, especially if the compressor is older. it will still get good and cold.

 

[The Critic]

2.5 lbs is the amount that Toyota recommends for R134A conversions on this particular vehicle.

 

[hal]

was it 3.5 for R12?