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Vent Temp 52 degrees

Big3 on Sun June 15, 2008 9:30 PM User is offline

Year: 1986
Make: Toyota
Model: Celica
Refrigerant Type: R-12
Ambient Temp: 82
Pressure Low: 25
Pressure High: 210

I just replaced almost the entire system in my 1986 Celica (R-12) - new evap, condenser, expansion valve, compressor. I recharged with R-12 with 30 ounces per the FSM. Site glass is clear (maybe too clear?). No bubbles at any time - when accelerating to 2000 rpm and back to idle. Problem is the vent temp only comes down to 50-52 degrees. Ambient temp is 82 degrees with 72% humidity. I even took her out for a 10 mile drive and the lowest the center vent temp got was 48 but stayed consistently at 50. Gauge readings: 25 / 210 at 2000 rpm, fan on high, windows down, doors open and a fan on the condenser. Cooling fans on the car were also operating. At idle, the readings were 35 / 175. Any suggestions?

mk378 on Sun June 15, 2008 10:16 PM User is offline

Make sure it's not reheating with the heater core. With a full charge and 25 on the low side it should be quite cold inside. Is the compressor cycling?

Big3 on Mon June 16, 2008 7:54 AM User is offline

Compressor is cycling. I'll check the heater but I doubt that is the issue as before the a/c is one, no heat was detected coming out. I would hate to break it open again since 2.5 cans of R-12 is quite a bit of scratch. How would oil fill affect the performance? I loaded it with about 8 ounces of mineral oil - putting 2 ounces in the evap, 2 in the condenser and 4 in the compressor. The Expansion Valve is brand new - the capillary tube with the bulb on the end attached to the same point as the old one. I wrapped it in some insulating tape.

mk378 on Mon June 16, 2008 9:21 AM User is offline

The compressor cycles based on evaporator temperature. It should not turn off until the vents approach 40 degrees. Maybe it is turning off early due to a sensor problem. The refrigeration system seems to be doing fine.

Big3 on Fri June 20, 2008 8:52 PM User is offline

I had the discharge hose repaired (replaced the hose using same fittings). The original hose had a OEM 180 deg bend but the new hose is straight so it had to bend in order to install and I am afraid that it has collapsed the passage a little (it feels oval shaped at the bend). What pressure readings would I see if the discharge hose is restricted partially? Would this cause the vent temp to be at 52 degrees? The compressor is cycling on/off. What would be a symptom of overcharge of R-12? I am trying to figure out more possibilities before evacuating that expensive R-12 to open the system back up for a look see.

Chick on Fri June 20, 2008 9:36 PM User is offlineView users profile

Did you change the drier? Is the suction line cold all the back to the compressor? If so, I agree that heater core is blending heat into the cold air stream, Feel the lines going into and out of the drier, should be the same temp..Let us know about the suction line... Hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

Big3 on Fri June 20, 2008 11:19 PM User is offline

Line from comp to evap is cold with condensation. Drier is neither cold nor warm. I clamped the heater hose shut to be sure and it didn't seem to have an effect. I was able to get a thermometer probe into the evap case all the way in and I saw temp go to 40 (this is when the compressor clutch seems to disengage. Still a ten degree diff at the vent (only 2 ft away). A/C compressor clutch seems to disconnect for a minute or so before engaging again. Seems like a little too long. There are two pressure switches screwed into the liquid line at the firewall before the tube enters the evap. Why two I wonder? The site glass only shows a few bubbles when the car is first started (cold) and comp is first engaged. I never see any bubbles after that - even when cycling. Shouldn't the evap temp be closer to 32 deg? I wiggled and flexed the discharge line and watched the gauge readings and that had no affect. At ambient temp of 70, humidity at 80%, my readings were 20/195 at 2k rpm.

bigkev on Sat June 21, 2008 12:54 AM User is offline


Edited: Sat June 21, 2008 at 1:28 AM by bigkev

bigkev on Sat June 21, 2008 1:27 AM User is offline

86 celica and mr2

1.70 to 1.90 lbs r12

oil 3.40 oz

low side 21 to 28
high side 199 to 220
*sea level, ambient 80F

With a pressure of 25 seems you should have spider balls when riding in that car!

Chick on Sat June 21, 2008 6:37 AM User is offlineView users profile

You are going to have to find where the heat is blending into the cold air from the evap..all seems to be working fine. Cold line from evap to compressor shows it's working, as does the 40 degree evap temp (evap will be colder)

Email: Chick


Freedoms just another word for nothing left to lose

Big3 on Sat June 21, 2008 11:46 AM User is offline

So the 40 degree evap temp is fine - I thought 32 was the norm. A 8-10 degree rise at the vent is excessive I take? It has a heater valve in the water line - it is closed but that is just by looking at the lever. I could replace it since it is cheaper than 3 lbs of R-12. My 95 Chrysler Concorde blows about 38 at the vent and freezes my ass off. I have even seen it dip to 32 at the vent before the comp recycles. What would the two pressure sensors at the liquid line be used for (two)?

mk378 on Sat June 21, 2008 12:07 PM User is offline

The evaporator core itself can't be allowed to cool below 32 degrees or it will get covered with ice which will clog up the airflow. 40 for the air leaving the evaporator (which is necessarily always slightly warmer than the core) is typical. This is controlled by a temperature sensor in or near the evaporator. Like any part, there will be manufacturing variations. The foam blocks and other stuff that prevent air from bypassing around the evaporator are also important for keeping the final air temperature close to the core temperature.

The two switches on the high side line are going to be either seperate high and low cutout switches, or one trinary cutout and one switch to control the fans.

Big3 on Sat June 21, 2008 2:40 PM User is offline

I removed the heater water flow control valve at the firewall. When closed I found that I can still blow a small amount of air thru the valve. A trickle of water would likely flow thru when its closed. Is the heater core isolated from the cold air coming from the evap by some type of door when the temp is set to cold? All doors controlling flow to top, middle and bottom vents work properly, as does the inlet door controlling where the air is drawn in from.

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