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More AC questions, more info this time.

CyFi on Tue August 19, 2008 2:05 AM User is offline

Year: 1987
Make: Toyota
Model: Supra
Engine Size: 3.0 GE
Refrigerant Type: R134a
Ambient Temp: 80
Pressure Low: 25
Pressure High: 225

Ok, so i took my car to a friend that works at a Toyota dealership and watched him as he tried to diagnose my system using a robinair machine. Sitting idle, fan on high, recirc on, windows down, vent temp of 57 degrees F. When bringing up the idle speed to about 1500 to 2000 low side pressure drops to 7-10 psi and high side slowly rises to about 250 highest, and at the same time the vent temps drop to about 54-55 maybe. Now, this is after sitting for about 10 minuets.

Before we did this, he evacuated completely and recharged the system with about 1.3 pounds or refrigerant.

After an unsuccessful trip to the dealership, i drive home in about 90-100 degree weather and get vent temps of 45 on the highway, right around where it should be.

The biggest problem i face, is it takes forever for the thing to cool off. If the cabin is hot i have to leave it on recirc for a long time before it starts blowing cooler and cooler. Driving around in town in 100-105 temps my vent temp doesn't seem to go below 55-60 unless i drive for quite some time. Short trips, the ac is pretty useless. My fan seems to be pushing a large amount of hot air, but i don't have the right equipment to test it, so i am replacing the fan clutch and switching to a larger turbo model fan in hopes to pull more hot air.

The system has been fully flushed to get all mineral oil out. Proper amount of ester oil has been added
Brand new TXV ( i saw these low low side pressures upon raised idle before with the old TXV too, so it makes me feel that's not the problem)
No air in the system at all.

PLEASE HELP! i dont know where to go from here, if i brought my car to Arizona Mobile Air would they be able to diagnose and fix my ac?! This has be an everlasting problem that nobody can seem to figure out. If R134a is the wrong choice i wouldnt mind switching back to r12!

Thanks for any and all help!

mk378 on Tue August 19, 2008 9:17 AM User is offline

You're probably undercharging it trying to keep the high side down, because the condenser is inadequate with R-134a. This causes the low low side and poor cooling. So you can try a few things, certainly improve fans, more R-134a (don't worry so much about high side getting into the 300's with a conversion and triple digit ambient). Or you can pull the 134a out and charge with R-12 without changing the oil. Evacuate for a long time to get traces of R-134a out of the oil so you're not running a mixture.

CyFi on Tue August 19, 2008 11:07 AM User is offline

Thing is when the previous servicer worked on it i think he injected some dye with oil into the system which probably happens to be pag oil. Now that thats in there, i dont know if i can switch to r12 without a full flush

TRB on Tue August 19, 2008 11:55 AM User is offlineView users profile

Quote
Originally posted by: mk378
You're probably undercharging it trying to keep the high side down, because the condenser is inadequate with R-134a.

I mentioned this in the previous post and got the response the condenser was fine its a OEM PF model. All my data shows this to be a serpentine condenser. My opinion is the system is under charged and may need a true PF condenser to work correctly with R134a.



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CyFi on Tue August 19, 2008 1:45 PM User is offline

The condenser may be a "serpentine" condenser, i thought there were only two types, and i knew it was not a single pass type. It seems like my car is not well suited for R134a, but the thing is so many supra owners with the same car and model and all have had great success with the retrofit.

Old Codger on Tue August 19, 2008 6:06 PM User is offline

While it won't solve your problem it would help if you verify that you have your air circulation selection lever set to "recirculate" or "inside air". Don't have "fresh" "outside" (hot) air coming into the cabin while you are initially trying to cool the cabin down. The 134A will be working hard enough to cope with the recirculated air.

OC

CyFi on Tue August 19, 2008 6:46 PM User is offline

It is always on recirculation mode.

TRB on Tue August 19, 2008 7:09 PM User is offlineView users profile

I would suggest putting the additional 3 ounces in the system. Make sure your fan clutch is working perfectly also!!

-------------------------

When considering your next auto A/C purchase, please consider the site that supports you: ACkits.com
Contact: ACKits.com

CyFi on Tue August 19, 2008 7:30 PM User is offline

I have a brand new oem clutch on order, and an upgraded fan. I will see how that helps, and add more refrigerant in after that if theres no improvement.

I have another question. If the engine doesn't ever get hot enough to make the fan clutch engage fully, then doesn't that mean it wont, regardless of AC condenser temps as those temps are too low to engage a fan?

Edited: Tue August 19, 2008 at 7:31 PM by CyFi

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