Automotive Air Conditioning Information Forum (Archives)

indaheat on Fri August 31, 2012 4:22 PM

Year: 1993
Make: Toyota
Model: Tercel
Engine Size: 1.5
Refrigerant Type: R-12
Ambient Temp: 105
Pressure Low: 90
Pressure High: 40
Country of Origin: Japan

Hello,

New to the site and want to say hello! I have also have a problem with a 1993 Toyota Tercel I hope you can help me with? This vehicle would not hold a charge. After injecting a dye into the system during servicing of the system I found no visible external leaks. Suspecting the expansion valve or evaporator leaking I removed the evaporator and saw that both the expansion valve and evaporator were leaking and some evidence of corrosion on the inside of the expansion valve and aluminum lines. I found a 1993 Tercel at a local pick your own parts wrecking yard and replaced my entire system with the components from the donor car: Evaporator, expansion valve, all lines, hoses, condenser and compressor. The inside of all the components and the oil was spotless. The receiver/drier was replaced with a brand new unit. All lines, hoses, evaporator, and condenser were flushed out with compressed air. I decided to use R-12 as I have some from my previous days of being a mechanic and A/C certified years ago. After installing everything and evacuating the system for an hour and making sure it held a vacuum I started the car and the A/C system. I first added a Toyota 1.4 oz ND-6 oil charge, then with a bulk cylinder attached to my gauges I slowly opened the low side valve and when the pressure reached 80 psi I closed the valve. I then slowly opened the high side valve until the compressor clutch engaged then closed it. With the compressor clutch engaged the low side stayed at 80 psi...it did not move. The high side went from 40 to maybe 50 psi. I suspected a faulty compressor.



Took the compressor I bought at the yard and replaced it with another used unit since they won't give you your money back when you buy the warranty only parts in exchange. Brought the compressor home, cleaned it up, drained what little oil it had in it and added 2 oz of mineral oil to the compressor. I installed it, evacuated the system, made sure it held vacuum, and I have the same problem...The high side pressure is 90 psi and the low side is 40 psi. The low side does not move and the high side goes to 50 psi when the clutch engages. The high side pressure will go higher if I leave the high side valve on my gauges open, but I only open the high side valve enough to get the clutch to engage then I usually fill thru the low side port.



Could I have two bad compressors in a row? Is there a blockage in the expansion valve or somewhere else? Should I continue adding R-12 to the system to get a "full charge" (I stopped when I noticed the low side pressure not moving when the compressor clutch engaged)? Am I doing something wrong? Any help would be greatly appreciated! Thank you in advance!

Edited: Tue September 04, 2012 at 7:15 PM by indaheat

GM Tech on Sat September 01, 2012 5:09 AM

Put a full charge in it and report pressures,, stop fooling around. You MUST "weigh in" the full charge. I don't even look at the guages until the full charge is in the vehicle....

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

Edited: Sat September 01, 2012 at 5:11 AM by GM Tech

mk378 on Sat September 01, 2012 11:25 AM

Test compressors off the car by holding your finger over the suction port to see if it will pump air when you turn it by hand. It's good practice to static pressure test R-12 systems with some other gas to be sure there are no (big) leaks before charging. GM Tech is exactly right you need a full charge to see what is going on. Running with a tiny charge is very hard on the compressor since no oil will flow and considerable heat will build up. Notice that A/C compressors don't have cooling fins on the outside like air compressors-- the flowing refrigerant is what cools them.

Edited: Sat September 01, 2012 at 11:29 AM by mk378

indaheat on Sat September 01, 2012 11:35 AM

Thank you gmtech. Will do. Not "fooling around" just thought I'd stop adding refrigerant if the compressor wasn't sucking/pumping it according to my gauges. Could you please explaing why the pressure doesn't drop on the suction side when the compressor clutch engages even though there is not a full charge in it?

I thought the signs of a system that doesn't have a full charge to be low pressure on the low and high side?

indaheat on Sat September 01, 2012 2:27 PM

Thank you mk378,

I did put my finger over the suction and discharge ports of the compressor and turned it by hand. It sucked my finger on the suction side and built up pressure on the discharge side on the bench. What other type of gas would you use to add a test charge to the system to test for leaks prior to charging it with R-12? I didn't run it with a tiny charge for very long. Maybe a minute and shut it off since I thought I had a problem. I'll add a full charge and report. Thank you all for the help!

94RX-7 on Sat September 01, 2012 4:40 PM

Nice. Your car uses the same Nippondenso TV series compressor that my RX-7 does.

Technically, the correct oil is ND-7, not ND-6. Does it make a difference? Who knows. Toyota and Nippondenso certainly thought so and specified two unique oils for the TV series. ND-7 for use with R-12 and ND-9 for use with R-134a. I've been trying to figure out what a generic substitute for ND-7 is, and everyone I've talked to has said mineral oil (ND-6) will work just fine.

You say it builds up pressure when rotating it by hand and your finger over the discharge port? After a couple turns does it build up enough pressure so that you can't hold your thumb on it anymore? Do you hear any gurgling or leaking sounds when doing this? A no-pumping TV series will generate a little pressure under your thumb, but you can hear the pressure leaking backwards through the vanes and back out the suction port.

I would suggest that you dump in the initial charge as a liquid on the high side until it won't take anymore then fire the system up. Compressor should spin backwards as the charge is going in on the high side.

You re-used the junkyard expansion valve? I would replace it. Might be stuck at full open and causing the pressures you're seeing? It is an *extremely common* (and therefore inexpensive) standard Nippondenso design.

What's your total amount of oil in the system? Sounds like you ran it with only 1.6 oz the first time? That sounds low. 1.6oz plus 2oz is closer to being "on the money" but is likely still a touch low. Make sure when you add oil to put it in the discharge port on the back of the compressor. There's a nifty little reservoir, oil separator and oil injector back there, and so any oil present back there will be immediately injected into the vane chamber where it is most needed.

Edited: Sat September 01, 2012 at 4:42 PM by 94RX-7

indaheat on Tue September 04, 2012 6:18 PM

Well,

Hooked up the gauges to the car the other day, hooked up my bulk cylinder to the yellow hose, turned bulk cylinder upside down, purged yellow line at gauge manifold by depressing shrader valve located on the manifold inline with the yellow hose until liquid r-12 came out. I turned the cylinder right side up and set it on my digital bathroom scale as that's all I have. Scale read 19.2 pounds.


I slowly opened the low side valve and the pressure rose to 100 psi then closed the valve. I opened the high side valve and the pressure also rose to 100 psi then closed the valve. Started the car, set the a/c to max cool and the pressures are 100 on the high side and 100 psi on the low side. Opened the low side valve and let it run for a couple of minutes. Kept checking the scale and there is no change in weight. Seems it's not getting sucked in or will the bottle pressure add the 1.54 pounds of r-12 the sticker under the hood states the system takes?



There is an increase of 5-10 psi on the high side when the clutch engages, but the low side still does not change. The cylinder still weighs 19.2 pounds. No cooling from vents. Auxiliary fan is running when the clutch engages. All pressures are at idle ~ 1000 rpm.



Edited: Tue September 04, 2012 at 10:32 PM by indaheat

Leggie on Thu September 06, 2012 3:59 PM

Bathroom scales are not capable of resolving the weight good enough. Digital ones are especially useless as they don't let you read out the weight change.

You step on it, it reads the weight. The weight is locked in until its unloaded and reweighed.
If compressor comes on but the low isn't coming down at all, the compressor isn't pumping.

Even with a stuck expansion valve, your readings are way out of range, so it looks like your compressor is shot. You now need to recover whatever charge you added before you can open the system again.