Air con repair/R134 conversion

Hi guys.
Firstly this is on a 1991 Toyota Supra 2.5TT JZA70 MkIII with R12 air con. This might be better answered by someone who knows about air con
etc....
My air con stopped working, had it recharged, and it barely worked after the recharge. I got it diagnosed and they found no gas in the system.
I managed to come across all of the equipment necessary to recharge with R134a myself so I thought I would go along this route instead of paying a garage to sort it for me.
I found the condensor was corroded and had a leak so replaced that. I also replaced the receiver drier with an R134 compatible unit. I removed all pipework and replaced O-rings and cleaned internally. I also removed the compressor and fitted all new seals, and new reed valves at the same time as cleaning all existing oil.
So everything apart from the evaporator and expansion valve has been removed and pretty much overhauled.
Put the whole system back together, dropped down to a vacuum for a couple of hours, then charged with the right amount of Oil and R134 refrigerant.
OK, the system now blows cold air, however I still dont think it is up to spec.
When I turn the car on in the morning from cold, and set the blowers to max cold I get 4-5 degrees at the vents for about 20 seconds. This then creeps up to 9-13 degrees and hovers around there for the rest of the trip.
If I plotted a graph of temperature against time I would have a smooth wave, going up and down between 9 and 13.
At the same time, if I put the gauges on the air con, I get 30-40psi low side, 130-150 psi high side, and the pressure goes up and down at the same rate as the temperature.
At 9 degrees the gauges are on 30/150, and as it creeps up to 13 the gauges tend towards 40/130.
Once the car is warmed up the temperature fluctuations also seem to in time with the radiator fan coming on and off for some reason.
I had wondered that I may be experiencing a partially blocked expansion valve, perhaps due to freezing, as initially I get good cooling, then as it goes between 9 and 13 it is freezing, and then defrosting and then freezing etc...... I did leave it pulled down to quite a heavy vacuum for a long time, and would have though after a few weeks of running, any remaining water would have been pulled out by the drier.
If I feel the low pressure pipe coming back from the expansion valve to the compressor it feels slightly cold, but not so much it is sweating. The high pressure side is definately warm.
Does any of this ring any bells with anyone. Can expansion valves deteriorate so much they make freezing more prone. I cant imagine it is a blockage due to debris as it is too periodic for the blockage to be something floating around, but then again I'm not sure.
Perhaps its something electrical. Maybe the coolant sensor is getting bad, and this is throttling back the air con somehow, as it seems to be when my radiator fan comes on, the heat starts to creep up, then the fan goes off and the system starts to cool. Or then again, this could be normal behaviour as you would expect the air con to work less when blowing hot radiator air through the condensor, however I see exactly the same behaviour when I am on the road and cold outside air is running through the condenser (which is before the radiator).
On the radiator fan side of things, it is only since I removed the condensor and replaced this, that my radiator fan comes on at all. As far as I can remember, it has never come on, and the temp gauge used to suggest that everything stayed normal without the fan, even when stood still for a long time. Perhaps I have distrubed something, or even fixed a problem I didnt know I had with the fan, or sensor.
So, any clues, anything to try before I get the evaporator out and replace the expansion valve.
Thanks for your time.
Graham Wharton
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On Sun, 30 Sep 2007 15:36:02 +0100, Graham Wharton wrote:

I assume this is degrees centigrade. 3-4 degrees (F) would indeed be C-C-C-COLD!!!
I don't know how well the AC worked before the swap, but you did go from R-12 to R-134. Big difference. Most cars get around the inadequacies of R-134 by using a larger compressor or letting the compressor cycle longer.
The other side is, that model Supra is not known for its excellent ventilation. My '88 3.0 can get downright WARM in the summer in the footwells, and blowing 'fresh' air doesn't help a whole lot.
You can also try to help the AC along by keeping the system on Recirculate rather than Fresh. This will take the cool air from the passenger's foot well and cool it further. THis helps keep the air colder, but works best on longer drives. Don't expect a great deal of cold air on drives less than 10-15 miles.
I'm looking into something called Freeze-12 for my Supra and my Mazda. It's supposedly a direct replacement for R-12 and is supposed to be colder than R-134. It is not well advertised. Does it work? I dunno. But it's about the same price as R-134 and I don't have to swap out a lot of parts to use it...
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wrote:

I'm sure you already know this but some of the R-12 substitutes are really butane or LP gas, I forget which. It works and won't cause any problems until you puncture the AC system and then, of course, you have a fire hazard.
Jack
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On Mon, 01 Oct 2007 00:54:26 +0000, Retired VIP wrote:

Um...yeah...YEAH! I knew that Jack!
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My house mate is just about to order freeze12 for his soarer 1JZ, exact same engine and air con system as mine, so I will have a good comparision. Will let you know.
I'm pretty happy with 9-10 degrees celcius to be honest. It keeps the car pretty cool in great britains climate, however every time I start my car in the morning, I get a tantilising burst of about 30 seconds of 4 degrees cool air, which then fades, leaving me knowing that it can do better.
Graham
Hachiroku ハチロク wrote:

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When one turns the controller to "max" one is merely circulating the inside air, thus drawing the hotter air from inside vehicle. It is best to use the normal mode and draw cooler outside air when starting. After the air is blowing cold, one should then switch to 'max' to recycle the cooler, less humid, inside air.
mike

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Most conversions need to replace the condenser for proper performance.

hmm, my Supras a/c has always worked great. Even on river trips were 120f degree is normal in summer.

eeeeeeeeek! no,no,no... hold's up cross at the evil Freeze-12. LOL
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On Tue, 02 Oct 2007 05:13:08 +0000, Danny G. wrote:

Well, at least someone hasn't PLONKED me!! ;)
What's wrong with Freeze-12? Any useful anecdotes? I'm not familiar with the stuff...
And to think, 3 years ago I could have bought 30 LBS of R-12 for $80...
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That stuff is just asking for problems in the future.
For what it's worth, when my Supra a/c needs work I will just replace the oil, condenser with a parallel flow coil and use the 134.

I stock a few refigerents but would not have bought that either even though list price is like $1,700! URI: http://www.uri.com/is-bin/INTERSHOP.enfinity/WFS/PrcTransaction/en_US/-/USD/ViewCatalog-Browse?CatalogCategoryID=OLOsEEGSSZ8AAAEVIV3dKyLq&OnlineFlag=1
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Assuming the corrosion was external or the entire system would be.

The problem with conversions is that the condenser needs to be bigger with a R134 system or the performance suffers. If your new condenser is a "parallel flow" type they are more efficient (= bigger) and the a/c performance should be fine.

That is within the normal range for the controls to cycle the compressor so the evaporator does not get to cold and freeze up.

> Once the car is warmed up the temperature fluctuations also seem to in

Something sounds odd here but I dont have enough informatin.
But the a/c condensers electric fan should only come on when the high side pressure is much higher due to the tempature outside being very high. I would check the belt driven fan clutch, pressure switch and your guages/pressures.

Ohho I missed this part. But if you are freezing internaly (why dont the guages show it) then the system is wet. More likely would be the expansion valve has the same corrosion. But thats just a guess.

Poor condenser air flow?

No. The tempature and pressure controls prevent the evaporator from freezing up and a dry system can not freeze up internially.

Check for corrosion. And the evaporator.

That electric fan should almost never come on. A high side pressure switch controls it.

That is normal operation.
Perhaps I have distrubed something, or even fixed

Over charged, low condenser air flow, internal blockage, would be common causes.

Test/find the problem before taking it apart.

Hope that helps Dan
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Danny G. wrote:

The corrosion was external on the condenser. It was affecting one of the pipe flanges. The aluminmium had gone really soft, so much so that it was impossible to remove the pipes without damaging the condenser. So a new condenser and pipes went in. There was no evidence of internal corrosion.

Yeahh, thats what I though. The car is fitted with a 10PA17 10 cyclinder compressor. The same compressor is fitted to later model cars which come from the factory with R134a, so I am assuming (maybe incorrectly) that toyota thought the compressor was man enough. Are all 10PA17's the same performance (certainly there is only 1 overhaul kit for them all, which seems to suggest that they all have the same innards).

On the JZA70 supra there is only 1 fan which does the air con AND the radiator. It is a hydraulic fan.
I had thought about the pressure switch to be honest. I was expecting the high side to be a little higher, and when refilling, the air con kicks in at almost 0psi, I would have expected it to wait for a little more low side pressure before cycling the compressor (aain, maybe i'm wrong. I'm no expert).
Its a cheap item to replace anyways.

Freezing internally, according to my books would give me a 0psi reading on the low side gauge right. Well I did see this when I first filled up the system. It wasnt working at all. I discharged and refilled a couple of times with no difference. I let it sit overnight and then ran it in the morning, when it cooled briefly and then stopped and the gauges went to 0psi low side. So i dicharged and did a very long deep vacuum, and recharged, which seemed to get rid of that.
So looks like my first attempt at filling, had moisture in it. I guess I could have saturated the receiver/drier, and it cant pull any more moisture from the system and I have a little bit left and it is freezing, but then again, I would have expected to see very low low side psi readings wouldnt i?

Not sure what to try there. The condenser has been replaced and all pipework removed and cleaned. I did use leakblock on the threads when refitting the pipes, perhaps some of this got into the pipe and is restricting (doubt it though, i was pretty careful)
The new receiver/drier i fitted wasnt a toyota item. It was a cheaper unbranded item bought from an air con shop. It was listed for the supra, and had R12/R134 compatible stickers on it. If this is poor I guess it could affect flow through the condenser.

Like I said before, there is no condenser fan. The only fan is the main engine/radiator fan, which I guess it can turn on if it needs to. Like I said, that engine fan never used to come on, and it is only since I removed and replaced the air con piping, and pressure switch, that it now comes on regularly. Also replaced the condenser, so I could have distrubed the radiator temp sensor too.

I have got a compressed air powered, ethanol based, air con flush kit. Would you recommend disconnecting hooking that into the system and doing a full flush, then vacuum and recharge oil/gas. I'm not too sure where to disconnect though if I do that. i.e would running the flush through the drier be ok.

What I might do is give the system a good flush. Replace the pressure switch and the expansion valve. Get a new toyota drier put on. Then put it all back together. drop to vacuum overnight. and regas.
Like i said, 10 degrees C cooling is fine for me. If it was normal to get a 20 second 4 degrees burst and settle back to 10 degrees when you first turn the system on, then I would be happy to settle with that, however if it should go to 4 degrees and stay there, then I will do more work on it.

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Thinking about this a little further, and looking at the layout of the system, there are no bypass pipes around the expansion valve (not that I can see anyway)
So presumable there is no way, other than turning on/off the compressor to regulate the air con system electronicaly.
When the gauges are fluctuating up and down (130-150 on the high side), and the temp cools and rises again, the compressor is full on 100% of the time and revs remain constant.
So the only thing i can think of is the expansion valve area and some sort of periodic blockage.
Correct me if I am wrong here....... my assumptions.
1. With the compressor on 100% you would reach a stable pressure and stable cooling effect.
2. No electronic control of the expansion valve, or any other valves in the system. Only electonic control is switching the compressor clutch on or off.
3. The effect of cooling air in the blower assembly, and this heating up the air post expansion valve, would not affect pressure in the system to any great extent.
Graham
Graham Wharton wrote:

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Under almost all normal conditions the controls cycle off/on the compressor because it is so oversized the evaporator coil would go below freezing and ice up. If that happens the ice would block the air duct and no air would come out the vents.

I doubt this is the problem

No, driving down the highway the compressor must cycle off to keep the evap from freezing up even when it's close to 40C degree outside.

True
No
This link to the 1990 TSRM may help. http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S &P=1 It has system test procedures and you can find links to parts pages there also.
a couple thoughts: Adjust the refrigerant charge on a 134 system using the sight glass (clear, no bubbles) will be over charged.
You can test for a condenser air flow problem by directing a large fan at the condenser or running cool water over the fins and checking gauge pressures.
On my Supra the compressor cycles off at about 4C degree when measured at the inside air vent.
GL Dan
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Danny G. wrote:

Thanks Dan,
All useful info. Just a point to note though, if I let my car warm up fully, air con on max cool, the compressor never cycles off. It is on 100% of the time. Is this because it is never reaching the ultimate cooling, and thus is never being shut off the the evaporator temp sensor.
Graham
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Your welcome.
Keep in mind there are a lot of things that would cause those symptom's so it may be cheaper for you to pay a technician to trouble shoot the problem for you.
For example check out #1 - 8 (especially #4) here: http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S &P
This do-it-your-self link may be more helpful: http://www.vintageair.com/DownloadsSection/Documents/Troubleshooting%20Guide.pdf
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