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87 Supra AC efficiency low (pics) Pages: 12Last

CyFi on Mon August 16, 2010 9:06 PM User is offline

Year: 1987
Make: Toyota
Model: Supra
Engine Size: 3.0
Refrigerant Type: R134a
Ambient Temp: 122
Pressure Low: See pics
Pressure High: See pics
Country of Origin: United States

Well its summer again and i am yet again having AC problems. The system is converted to R134a a while ago. I took the entire system apart, replaced the receiver, flushed all lines, drained compressor, installed a new TXV, flushed evap/condenser and replaced all the seals. Then i refilled the system with R134a. The AC works fine most of the year, but come summertime in AZ it really struggles, especially at idle. Driving around town the AC gets *cool* but not cold (~65 deg) and on the highway it gets better (~48deg). I will let the pics do the talking...

Ambient temp in deg F

This is where i placed the probe

About 15 mins after a hot shutdown

Engine started, AC off

AC on high, recirc, engine idling after about 5 mins

Vent temp

Condenser inlet temp

Condenser outlet temp

Raised RPM to about 1500, left for about 5 mins, then took pics

Vent temp:

Condenser inlet temp

Condenser outlet temp

After spraying in front of the condenser with cool water: (about 50psi drop in high side pressure)

No change in vent temp...:

This entire time the suction line is barely cool, any water on the line is from my spraying the condenser, no water condensed on the line on its own:

I am really at a loss, pressures seem about normal but vent temps/suction line temps are terrible. I have bypassed the heater core as well, so that is not a possible cause. The engine also has a brand new OEM (from toyota) fan clutch(1 year old). I also experience minor overheating with the ac on at low speeds especially after exiting the highway. Thanks for any help you guys can give me, i have tried my best to figure this one out myself but im not a professional and have come to the point where i dont know what else to try. Thanks.

Edited: Mon August 16, 2010 at 9:16 PM by CyFi

Dougflas on Mon August 16, 2010 11:43 PM User is offline

Do you really expect us to convert metric measurements? Your gauges are tough to read.

1stbscout on Mon August 16, 2010 11:56 PM User is offlineView users profile

Without much more than looking at the temps at the condenser I can tell you a couple of things.
Either the temps shown are not accurate OR.... the condenser is not doing a very good job.
This is either a airflow issue or ?? The temp drop between the in and out is not enough. The high side pressures indicate a lack of cooling at the condenser.

The low side pressure at 1500 RPM is very low assuming the fan is on high, re-circulating air, Doors open ...... the 60 degree temp at the vent is not as bad as you think. Still at 20 psi on the low the evap core should be at a -4 or 5 degrees. This would cause icing on the evap core and limit air flow. It is highly unlikely, if your low side is at 20 that you have 45 or 50 degrees of superheat.

This would lead me to believe you are not at a full charge yet. Or you are having a problem with the expansion valve.

Either way in order to attain proper cooling you are going to have to find a way to get the condenser outlet temp closer to ambient temp.

1stbscout on Mon August 16, 2010 11:58 PM User is offlineView users profile

One other question.... Is the core I see in the photos a intercooler?

CyFi on Tue August 17, 2010 12:32 AM User is offline

Thanks for the tips. If you look at the center black scale, it shows it in PSI.

Im not sure what more i could do for air flow because it has a brand new fan clutch (yes, the fan was roaring like a semi truck) and everything is stock. Yes that core you see is an intercooler, completely stock system. All fins are strait and clear for good airflow. Could it be that my condenser has internal damage not allowing it to release enough heat? Is it just that the stock condenser is not cut out for R134a? Only thing is many have had success with converting with the stock system. The 60 deg vent temp was sitting in the shade as well, out on the highway in traffic in full sun there is no way at idle that i would be at 60 deg vent temp. I have taken many cars out on the road and sitting idle the ac is so cold it hurts my hands, i see no reason why my system shouldn't be able to do the same, but it never has.

And also i cant see the evap freezing as the low side line coming out of the evaporator is barely even cool. Thanks a lot for the tips again.

mk378 on Tue August 17, 2010 9:17 AM User is offline

Search for some of NickD's old posts about his Toyota Supras. I think the bottom line was that they just don't work with R-134a. Convert back to R-12.

iceman2555 on Tue August 17, 2010 10:09 AM User is offlineView users profile

Agreement to return to R12. The entire AC system is set to work with this refrigerant and will perform much better. Noticed that there is a thermocouple attached to your DVM...why not use this for your temp measurements instead of the infra red. Infra red's are not the best for use in severe heat laden areas.
The discharge temp seems a bit high....almost near the point of a condenser restriction. However, the drop is not sufficient to indicate a condenser restriction. It is possible that the temp readings are contaminated with surrounding heat sources. Prefer the use of a thermocouple over the infra red.
The pressures and vent temps indicated...considering the ambient temp (122 degrees) and engine PRM are sufficient for a 134a conversion. The condenser in this vehicle seems to be a serpentine flow unit. This was the first 'hi performance' condenser that employed multiple flow paths for enhanced cooling performance. Unfortunately, this was the first condenser that could have severe restrictions and not be able to be thought cleaned.
First suggestion would be to return to 12. Secondly insure that the system is properly recharged with 134a. Unfortunately, the use of pressures is not a true indication of proper recharge. This is exacerbated by the operational pressures of 134a vs the pressures of 12, combined with the use in a system that was never designed to operate with 134a.
One other issue....was the TXV an OE Toy unit or was an aftermarket valve used? Have seen many instances where the aftermarket unit did not match the heat index of the OE unit.

The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
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NickD on Tue August 17, 2010 1:50 PM User is offline

Have an 88 like yours, still has the original R-12 charge in it, oil capacity is 5.6 oz, believe the refrigerant capacity is 28 ounces, but would have to recheck the manual on that.

Recommended means of charging is at 86-95*F, doors open, AC on, blower at max, with a cleaned system, to charge via the sight glass with an engine speed at 2,000 rpm until you get a clear sight glass, I may leave a bubble or two. Toyota says to use the manifold gauges for a general check, but specify 28/206 L/H psi at 86*F.

With a clear sight glass, you are pouring in pure liquid from the receiver into the expansion valve. Have to say the AC system on this car kicks butt, even use it occasionally with the removable top in the hatch for an ice cold breeze on those super hot days.

Did you know its a mortal sin to put anything but R-12 in a Supra? If you do, can experience hell, but maybe you already are, told its hot in hell.

CyFi on Tue August 17, 2010 11:44 PM User is offline

Alright, thanks everyone for the help. Looks like the consensus is to convert back to R12. Im a local AZ resident, so im going to take the car over to the pros at azmobil air and get a quote, im tired of fumbling with the system, and they have all the proper tools and equipment to do the job right. Hopefully the price for a job like this isnt worth more than the car

CyFi on Mon September 13, 2010 5:58 PM User is offline

Ok i converted the system back to r12...still not happy.
Heres what i did for the conversion
-Flushed all lines and components - Done professionally by AMA
-All new seals
-New TxV
-New Reciever/dryer
-New compressor
-8.4oz mineral oil
-Recharged professionally by AMA with R12
-New OEM fan clutch about 2 years ago

After all this, I am still getting poor AC performance. Cruising on the highway, no problem, low speed, its poor in my opinion until i have driven around for a long period of time. Sitting idle, forget about it.

Car sat in the sun, its a 94 degree day, got in the car, turned the ac on for a minute, started driving home, my place is 2 miles away and im sweating the whole way back, blows very moderately cool. Parked it under the covering and after sitting idle for a while vent temps were maybe high 60's... if I hold engine speed up at 2500 rpms for about a minute the clutch fan is roaring and vent temps come down to high 50's(keep in mind the car is in the shade).

The fans kick on at about 275 high side psi i believe, any idling and the fans kick on, some bubbles appear in the sight glass(not foamy), raise rpm for a long amount of time, fans kick off, vent temps come into the high 50's, most if not all bubbles gone from the sight glass. Spraying water on the condenser with a sprits bottle didn't show any change in vent temps or sight glass bubbles.

All this is with fan on high, recirc, windows open

Heater core is bypassed, so that is not a possible concern, suction line is barely cool at idle, gets cooler with rpm raised long periods of time.

Please help me, no matter what i seem to do the ac on this car just sucks. I get into my friends Hyundai, kick the ac on after the car has baked in the sun and i get instant 50 degree air, why cant this car do that?

EDIT: Using a Raytek gun, condenser inlet seems to be around 180-185 while outlet is around 145-150 at idle. System was evacuated, leak tested and charged by AMA last Friday.

Edited: Mon September 13, 2010 at 5:59 PM by CyFi

ghiotom on Mon September 13, 2010 7:45 PM User is offline

I feel your pain. We have a 2009 Honda Accord, 2006 Chevrolet Silverado 2500HD Diesel, and a 2007 Toyota Tacoma and all 3 will deliver low 40's vent temps with blower at full max in 95 degree weather at IDLE. But, my 1996 Jeep Grand Cherokee under similar conditions, maybe low 50's and that's after a little re-engineering (dual condensers, electric fan). I know the Chevrolet has the same CCOT system as the Jeep, so my guess is the compressor is just more efficient.

CyFi on Tue September 14, 2010 12:11 AM User is offline

OK well i just ran my AC again tonight, blowing 60 degrees, which i know for a fact is much warmer than it was before, and there are bubbles apparent, so im pretty sure im safe saying there is a pretty significant leak. Does anybody know how AMA does their leak tests before filling a system? Before getting my system charged they supposedly "pressure tested" the system for leaks (i assume with nitrogen) and it turned up nothing but i lost a significant amount of refrigerant in just 4 days, so how effective is this leak testing? Also, not really sure why it leaked, as it has brand new o rings all around, looks like its leaking from the receiver dryer connections, i can see some oil around them.

NickD on Tue September 14, 2010 6:25 AM User is offline

Not sure why you are not addressing your issues directly to AMA.

What is your history on this car, did you own it 22 years like I owned mine or did you just get it? Did your system every perform well? Have to say the AC in this vehicle is pretty darn good. Were things checked for good airflow for both the condenser and the evaporator, like debris between the condenser, radiator, and the air cooler. And debris build up in the evaporator system.

This vehicle has a very complex automatic temperature control system, even more complicated than you would fine in say a Cadillac. Not sure why you have your heater core bypassed, also a part of the system. Proper function of the automatic blend door, with good seals is equally important, even with the heater bypassed. Also don't know anything about your contract with AMA, was it to get the system operating to factory specifications, or just do the very minimum to convert it back to R-12?

Maximum oil capacity is 6.2 ounces, refrigerant capacity can vary between 1.3 to 1.7 pounds but the actual amount is determined by both low side pressures and obtaining a clear sight glass with doors open, maximum cooling, full blower manually controlled, engine running at 2,000 rpm with a targeted low side pressure of 28 psi at 90*F, high side in the 220 psi range. Can add 3-4 more ounces of refrigerant to fill up the receiver, I prefer to add just enough to see a bubble or two at these specified conditions. Going back in a couple of weeks under the same conditions, if you see more bubbles or even a lot of them, this tells you instantly if you have a leak. But if you add additional refrigerant, will lose that first before more bubbles are shown.

Even with your heater bypassed, can still have blend door problems allowing hot intake air to be bypassed into your vents. While some people jump up and down and claim Japanese cars are far superior to American cars, I am going to be honest. Toyota leather and rubber sucks compared to what we made here in that same era. The interior on my 92 DeVille still looks brand new, where Toyota leather splits in the sun after a couple of years. I did not want leather in mine. I also had to replace a lot of rubber in my Supra, that equally sucks, weathered and cracked already, rubber in my DeVille is still perfect and very pliable. But the Supra does have its other good points. For all you know, your blend door rubber seals are shot and you are bitching about other things because you really don't know this car. This car has six individual computer systems all data linked together, LOL, even a challenge for me at times.

Somehow a Supra owners club got a hold of me and asked me to join, didn't stay there very long, way too many idiots for me, I deleted the link. Since I recently purchased a Bayliner boat, joined their owners board, running into the same thing. Seems like the people with lots of money for a far superior boat that I have are not only arrogant, but stupid as well, can't tell them anything, so why even bother.

This always was a good board, lots of competent people here, probably why I stayed here so long.

CyFi on Tue September 14, 2010 10:46 AM User is offline

Thanks for your response NickD, your opinion is valued. I'm not sure where you got 6.2 oz of oil from, by checking another thread on here and confirming with the NAPA PDF it actually said 8.8 oz, but will that make a significant difference if it is overfilled? The system actually worked pretty well when i got it back from being charged, but i had assumed no leaks were present because they leak tested the system, and was a little agitated the performance was low (i figured it was hotter out than when i first got the car charged). I have had the car for over 3 years, the ac system never has worked 100% from the time i bought it.

The only reason i included extra info like the heater core being bypassed (has a small leak, next thing on the list to replace) is so that you guys don't send me down the path of checking blend doors and heater valves, but regardless it seems that i found my problem, i will have AMA check it out.

I have another question though, when is it appropriate to see bubbles in the sight glass? I noticed, even right after getting the system charged, that during idling, blower on high, high ambient temp, i was seeing just a small bubble at the top of the sight glass, i assume that is pretty normal for low airflow conditions like idle?

Edited: Tue September 14, 2010 at 12:02 PM by CyFi

NickD on Tue September 14, 2010 12:21 PM User is offline

As long as the dual function high switch sees at least 45 psi, the compressor will run, and sees this at much lower operating temperatures like 40*outside at which point you will see a lot of foam in the sight glass. Gave you the targeted low side pressure at the stated conditions for obtaining a clear sight glass. Also will see more bubbles at idle rpm, compressor isn't running at rated speed anymore at idle, and perfectly normal for the differential pressures to decrease and vent temperatures to increase at idle. But 60*F sounds high, should be more like 50*F. No vehicle recommends extended idling with the AC on. Hardly notice it when sitting at traffic light.

5.7 ounces is mean, 6.2 ounces of oil is maximum according to my shop manual. Over eight ounces is high for a system with a mean refrigerant capacity of only 24 ounces. Where did you get that number from?

If you saw a little oil on the receiver, you would see that my work as well, also lubricate those fittings with refrigerant oil when installing to assure a good seal.

CyFi on Wed September 15, 2010 4:38 PM User is offline

Thats where i got the info for the oil amounts.
Took my car back to AMA, they found 2 "very small" leaks on the rubber hoses, and one on an o ring, they fixed that, vac, recharge, and i was on my way. AC seemed to work great after i picked it up, i guess it had been sitting in the shade the whole time anyways, blew about 45 degrees on high/recirc. Just went to the grocery store, parked it outside in the sun, after i got back, turned the car on and ran the ac for 3-4 mins maybe while i loaded up my stuff, took off and drove the rest of the 3 or so miles which was kind of stop/go/45mph driving, ac blowing 60-65 degrees the whole time.. I have come to the conclusion the ac system in these cars suck butt, any heat soak and they just cant keep up. AMA says its working properly, i say its not, who knows, their word against mine i guess. Im going to install a pusher fan in front of the condenser and see if that makes any difference, but even idling and spraying the condenser with a spritzer temps only came down to 55 deg. Really frustrating that after spending about a grand on the ac system alone on this thing it still doesn't keep me cool. If anyone has any tips on how to improve the ac in this thing please help me out.

robs on Wed September 15, 2010 6:48 PM User is offlineView users profile

I do understand your frustration with all the money that you have spent. I would highly recommend adding a auxiliary fan and seeing what results you get after that. The air seems to be traveling trough the intercooler first pushing that hotter air onto the condenser. Maybe that is a poor design, but who knows. Keep us posted and if the system seems to not be working to its full potential, bring it back once again and we'll be sure to do our best to get it up to par.

Edited: Wed September 15, 2010 at 6:49 PM by robs

CyFi on Wed September 15, 2010 7:55 PM User is offline

Thanks a bunch Rob, i know you guys are probably sick of seeing me, it just seems like it works good when im there but as soon as i start driving around in the heat it struggles. I will let you know how the fan helps me out and go from there, but i am starting to believe the system is just not made to handle a lot of heat.

TRB on Wed September 15, 2010 9:02 PM User is offlineView users profile

I spoke with the mechanics after reading the previous message. They really went over it well and were surprised to hear it was not cooling well.

We have options here.

1. Bring it back we don't mind you paid for a service and we prefer to have happy customers.

2. It's not super busy now. Wait until it acts up and then just swing by the shop.

We're here to work with you and try to get this to cool you off in this nice weather we have.


When considering your next auto A/C purchase, please consider the site that supports you:

CyFi on Mon September 27, 2010 6:22 PM User is offline

Well since i had it in to you guys it seemed to work a little better. For some reason every time i take it to you it blows ice cold the whole way home but the next day it seems to be back to its normal self. It was actually working a bit better than before, after the last time i brought it in. I also got all my windows tinted. This morning i used the ac (was like 75 outside) and it blew ice cold, today, about 93 outside i used it and it blew mildly cool, around 60, and would warm up significantly at idle. At one point, at idle in the sun the compressor was cycling on and off, vent temps were warm and it seemed as though the compressor was bogging the engine down more than usual. I brought it home and in the shade, hood up, i held the engine at 1500 for 5 minutes strait and temps didn't go below 60 deg at the vents. As soon as i let it back to idle temps climbed back up to about 70-75. Seems very sporadic how it works, when there's not a huge load on it it can blow ice cold but as soon as there's any significant heat load on it, it blows warm. Still lost here, do you guys have anything else you can try? Its very difficult for me to make it all the way over there every time it acts up, and sometimes if i run the ac for as long as it takes me to get over there it will get fairly cool.

TRB on Mon September 27, 2010 7:02 PM User is offlineView users profile

My personal opinion is that 3 inch thick aftermarket inter-cooler is not helping things. Pressure readings where fine in the shop! No telling what they are after driving a few miles and sitting at a light with traffic in front of you. Only way to figure that out is to put some gauges on it and tape them to the window and watch the readings. Might not be an easy thing to do with your setup.


When considering your next auto A/C purchase, please consider the site that supports you:

JACK ADAMS on Mon September 27, 2010 7:15 PM User is offline

When you installed the TXV, did you make sure it was clipped on the suction tube and re-wrapped?

CyFi on Mon September 27, 2010 7:45 PM User is offline

TRB, the inter-cooler isn't aftermarket, it is completely stock. It shouldn't be creating any heat unless im doing some spirited driving anyways, which i never am with the AC running. I have tried the idea with the gauges but the location of the ports just doesn't allow it. I will give it another shot, but i need to get my gauges vacuumed down first since they have r134a in them.

Jack Adams, yes the sensing bulb was clamped tightly to the suction line in the stock location and wrapped with the foam-like wrap that was there previously

TRB on Tue September 28, 2010 12:47 AM User is offlineView users profile

What concerns me is if air flow is blocked. Sure did not seem like there was a lot with that big inter-cooler in there. Again I was out in the shop with Jack and the pressures were good in the shop.

I guess I would start digging in the air servos next. Have to make sure that no mixture of cold & hot is going on. You also have a ambient, solar and cabin sensors that could be changing performance on you.

Connect jumper lead from battery positive terminal to terminal No. 10, and a negative jumper lead to terminal No. 11 of servo motor connector. See Fig. 7 .
Ensure that servo motor lever moves smoothly from warm to cool position. Reverse jumper leads on servo motor connector, and make sure that motor lever moves smoothly from cool to warm position.
While operating servo motor in step 1) or 2), measure resistance between terminals No. 5 and 6. Resistance values will successively decrease from cool to warm position. If motor does not operate as specified, replace servo motor.

Position Resistance (Ohms)
Cool 1700-2000
Warm 150-250


When considering your next auto A/C purchase, please consider the site that supports you:

Edited: Tue September 28, 2010 at 12:48 AM by TRB

CyFi on Tue September 28, 2010 2:32 AM User is offline

OK i have the service manual for this car so i will go through all the motors as you described, but if it makes any difference, the heater core is completely bypassed so no addition of heat would be there, and the suction line leaving the firewall becomes warm to barely cool when the vent temps rise. Im also going to hook up my gauges and if nothing else, i will leave them tucked in the engine bay, and pop the hood/take a look at them when it starts acting up. I will post up the results of all this.

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