AC question

J

JT3HN86R

New member
This is a pic of the gauges low and high side pressure readings while the truck is idling. The low side is a little high but probably within the specs that are 36.25 PSI . THe high side is supposed to be max at 227 PSI and you can see that it is around 270 PSI. I don't know alot about AC systems. Can someone tell me if the unit is overcharged or what is happening with this ? The outside temp was about 83 degrees at the time. THe air blowing out the vents on the dash is cool, but not COLD like other 4Runners I have owned.
This is a 1998 Limited Auto with 3.4L.

TIA

IMG_0417.jpg~original
 
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Saved said:
Here are some links that might help.

Understanding Auto A/C Manifold Pressure Gauge Readings - They do not tell you how much freon is in the system!

Troubleshooting with Gauges FAQ

Auto Air Conditioning Repair 101 | CinciTDI.com

Part 2. How to properly charge an auto AC R134a refrigerant air conditioning system. - YouTube
Click to expand...

I have actually read through all of those sites previously and there is no answer to my question. The question is: Why is the pressure on the high side so far above specs?
 
Got a thermometer to measure how cool it is coming out of the vents?

The FSM says to check the readings with the AC on max,doors open, and at 1500 RPMs. This has worked for me measuring low side pressure with the el cheapo gauges.

Maybe the drier is filled up with shavings, crap, etc.

Paging Singtoe....
 
LittleCaesar said:
Got a thermometer to measure how cool it is coming out of the vents?

The FSM says to check the readings with the AC on max,doors open, and at 1500 RPMs. This has worked for me measuring low side pressure with the el cheapo gauges.

Maybe the drier is filled up with shavings, crap, etc.

Paging Singtoe....
Click to expand...

I'll second the Singtoe page............................
 
The high pressure side will read higher then normal on really hot days. The Condenser is not cooling down enough. Not enough air is flowing through the condenser.

A Simple test would be to hook the gauges up, get a water hose and spray the condenser down to cool it. You will see the high side low down to within specs.

The Overfilling won't necessarily mean higher H side pressure.
Overfilling will have higher low side pressures though.

You will have to do the sight glass test if you think you overfilled it.

Remember, the 4runner only takes 20 oz so if you put in 2 cans, you overfilled it.

Look at the glass. It is on the receiver drier in front of the condenser. Have a buddy turn the AC on and you should see the glass sight fill up with a car liquid. If you have too little Freon in it, you will see lots of bubbles and it not turn to liquid.

Have your buddy turn off the AC and withing seconds, the sight glass will turn from liquid to bubbles to nothing. If it takes more then a 6 seconds to disappear, you have too much Freon in the system.
 
Singtoe said:
The high pressure side will read higher then normal on really hot days. The Condenser is not cooling down enough. Not enough air is flowing through the condenser.

A Simple test would be to hook the gauges up, get a water hose and spray the condenser down to cool it. You will see the high side low down to within specs.

The Overfilling won't necessarily mean higher H side pressure.
Overfilling will have higher low side pressures though.

You will have to do the sight glass test if you think you overfilled it.

Remember, the 4runner only takes 20 oz so if you put in 2 cans, you overfilled it.

Look at the glass. It is on the receiver drier in front of the condenser. Have a buddy turn the AC on and you should see the glass sight fill up with a car liquid. If you have too little Freon in it, you will see lots of bubbles and it not turn to liquid.

Have your buddy turn off the AC and withing seconds, the sight glass will turn from liquid to bubbles to nothing. If it takes more then a 6 seconds to disappear, you have too much Freon in the system.
Click to expand...



The air sometimes is very cold and sometimes not. IT seems like the air is cold when I am driving and the air is only cool when sitting at idle.
Could the condenser be dirty on the outside ?
 
JT3HN86R said:
The air sometimes is very cold and sometimes not. IT seems like the air is cold when I am driving and the air is only cool when sitting at idle.
Could the condenser be dirty on the outside ?
Click to expand...

That is when you need to look at the AC gauges.

They can tell a lot when things are not working.

Dirt condenser is highly unlikely. If it was that dirty, your engine would over heat.


It is quite possible that there is too much Freon and when the condenser temps are right, the head space is perfect for the the vaporization from liquid to gas. This will give you your cold air when driving but cool air when standing. This also could be the same symptoms as having not enough Freon too. But by your gauges in the OP, it does seam high or over charge.

Did you add any Freon to your 4runner? If you didn't, definitely do the sight glass check to see any bubbles
 
Excessive high side pressure can also indicate non-condensables in the system, ie: Air. Was the system out of refrigerant and then you charged it?

When youre driving, there is airflow across the condenser, this lowers the high side pressure and temperature (because your cooling the R134a) which in turn lowers the temperature of the air coming out the vents.

The condenser is likely a little dirty, but unless there it is clogged, it should be fine.
 
Yes, I did add a little. Evidently too much. Now----how to remove some of the r134? I assume it needs to be evacuated by someone with the equipment and then recharged?

TIA for all the help.
 
JT3HN86R said:
Yes, I did add a little. Evidently too much. Now----how to remove some of the r134? I assume it needs to be evacuated by someone with the equipment and then recharged?

TIA for all the help.
Click to expand...

If you have an empty Freon can, hook it up to your gauges and open the valve and let the freon back into the can. Do with the 4runner off so your not over pressurizing the can. Some times works, some times doesn't.

Or if you are not environmentally conscious, just vent it out like every other country besides the USA does.
 
You mean IF I lived in another country I could just release some Freon back out of the system through the low side port ? I guess just let some out and re check the gauges ? Of course I wouldn't do it in this country. Thanks again Singtoe.
 
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