Chris or anyone - A/C questions inside

[MalcolmV8]

Chris,

I completely forgot you're an HVAC technician by trade and should have asked you a long time ago. I've been having trouble with the A/C on my Tundra ever since I got it in 2008 and not sure what is causing the issues.

There have been many threads on it and much troubleshooting. This summer I attempted to tackle the problem yet once again. Here are two threads on it that pretty much explain it all.

http://acsource.net/acforum/viewtopic.php?f=1&t=8701

and this one

http://www.tundrasolutions.com/forums/1 ... ta-tundra/

In summary I only get cooling when cruising down the highway. When I come to a stop the high side goes very high 425 ~ 450 PSI and the compressor cycles and vent temps are warm.
I've replaced the fan clutch, shroud is good and intact, I've pulled radiator and condenser apart and made sure there's no dirt or anything blocking air flow. I don't believe the issue to be air flow related. I think there's something wrong with the a/c system itself but not sure what.

Thanks
Malcolm

[cgrey8]

Here's my thought process.

When the high pressure side gets into the 300s, that's an indication that you have either too small of an orifice tube (assuming you have an orifice tube setup) or too much refrigerant in the system.

When the system is cooling, you'll have refrigerant in the evaporator and condenser when the AC is running. What's in the evaporator will be boiling off at fairly low pressures that boil the refrigerant in the 40-55°F range (pressure dictates the temp the refrigerant boils at). When the system is low on refrigerant, you may have the evaporator at the right pressure but there's not enough refrigerant in the evaporator to stay boiling and keep the entire evaporator at the target temperature. With a properly charged system, you'll have the inlet and outlet temp of the evaporator at the same temperature because there's a small amount of refrigerant still boiling at the output of the evaporator IF you have an accumulator dryer like Fords do. The accumulator is in the engine bay to absorb engine bay temp to help boil off the rest of the refrigerant so the liquid does NOT get into the compressor. Compressors only compress gas, not liquids. Liquid in the compressor is a BAD thing. Now I don't know the Toyota AC system today, but in the 90s, Toyotas didn't use low pressure accumulator dryers. They use high-pressure receiver dryers. In those cases, you have to make sure the evaporator boils off all the refrigerant before it gets out and into the compressor.

If the system is low on refrigerant, you will not be able to over-pressurize the condenser into the high pressures you are seeing regardless of whether the orifice tube is the right size or not.

With a properly filled system, you can easily pressurize the condenser too high and starve the evaporator of refrigerant because the orifice just isn't big enough to feed the evaporator so all the refrigerant ends up in the condenser. Even though the temperature isn't that high, the pressure is just because there's so much refrigerant in the condenser. Even though the evaporator will be very low pressure, the temp of the air that blows across it will be warm because there's just not enough refrigerant to boil and cool the air. So what you need to know to determine if this is happening is a gauge on both the high and low pressure side. This problem is indicative of the compressor cycling because the low pressure switch AND/OR the high pressure switch cuts the compressor off when either limit is hit. Older AC systems like my 89 Ranger only have a low pressure switch.

Now ASSUMING the orifice tube (or whatever metering system Toyota uses) is correct, an over-pressured condenser would indicate that you have the condenser OVER filled. There's so much refrigerant in the system that the compressor can't vac down the evaporator to a low enough pressure to get cooling because the high pressure side is either too high for the compressor to raise any further OR the high pressure switch kicks the compressor off so it never can get the evaporator pulled down low enough. So again, you need a gauge on both high and low side to see what is happening.

Hope this helps...

[MalcolmV8]

Hey Chris,

I have a manifold gauge with high and low pressure readings. Take a look at the first link I posted above. 5th post on there is mine with quotes of my pressure readings I took last summer. As you can see high pressure side gets very high.

I also suspected either over or under filled system so yesterday I completely evacuated the system and pulled a vacuum for around 35 minutes or so and then charged in fresh r134a. Same issue as before.

This system is rather odd. It has a dryer accumulator integrated into the condenser so the only way to replace the dryer is to replace the condenser. $207 + tax from my local auto parts.

There is no orifice tube but instead it uses an expansion valve which I suspect might be suck open (cause I have no clue what else lol) so I ordered a replacement and will try and install it this weekend. I hate to just blindly replace parts and see what fixes it but I'm out of ideas and getting beyond my understand of A/C although I'm trying to learn.

[cgrey8]

Relieve the system of some pressure. Even though you think it is properly filled, the numbers tend to indicate that you are over-filled. Relieve it down to the point where the high side doesn't/can't get to 425PSI.

[MalcolmV8]

I've done that. I had it hovering around 250 on the high side and it still didn't cool. The only thing it changed was that the compressor no longer cycled. I also noticed highway cooling was reduced too.

Also not sure what this means but the condenser gets so freaking hot or so it seems to me. 160F I measured yesterday in the cool late evening. If I take a garden hose and cool it the high side pressure drops a good 150 PSI and the vents will start to cool some as long as I keep the hose pouring on the condenser.

[cgrey8]

That is starting to sound like some problem. Do you have a laser temp gauge? If so, probe around on the condenser and see if there are hot spots. If it is only hot in areas, then that would tend to indicate that some of the runners are stopped up. I don't know if this is your problem, but it is starting to sound like the condenser is just not cooling. If you can run water over the condenser and it cools on the evaporator, then it is clear the condenser is NOT doing the job for whatever reason.

[MalcolmV8]

I don't have a laser temp gun but I do have an IR unit I can point at smaller locations. Good idea on the hot spots. I'll try hitting different spots and see if I get different temperatures.

[v8ranger]

I had the same problem with my wifes Maxima. She said it was not cold. I went to put a can of freon in, when I hooked it up it said it was full. But the pump would not turn on. It was showing on the hight side for pressure, so I let some out, it still didnt work. So I put back in what I let out and added more and it kicked on and got very cold. The gauge says its very high in pressure. I just took it as maybe the nissan's ran on more pressure. I have never owned one before, or had to work on the a/c system in one. I dont know if they have to run on more pressure than a amarican car or not, but, So far so good for me right now.

[MalcolmV8]

Chris, minor delay as our warm spell passed and we have some cooler weather now and even rain in the forecast so will resume troubleshooting once the weather picks up again.

[MalcolmV8]

Well I got a new a/c condenser ordered and I have a new expansion valve too. The condenser was free... sort of. Turns out the dealer I purchased the Truck from ripped off customers with unlawful document filing fees. Someone took them to court in some big class action law suite and won so the dealership mailed everyone a $400 gift card. I used mine to order a new condenser. $315 + tax.
I'll try get those installed in the next few days and see what that does. With our hotter weather now I really need a/c again when stopped in traffic.

[MalcolmV8]

New a/c condenser installed as well as expansion valve. The expansion valve was really tough to get to. I had to pull out the console and entire lower part of dash to pull out a/c box with evaporator and expansion valve. The evaporator was full of dirt and mud from the prior owner wheeling they heck out of the truck. I cleaned the evaporator really well with hours of garden hosing, buckets of water etc.

A/C works a ton better but still fails to work when you come to a stop. Vent temps will go from about 40F to around 60F or higher once you come to a stop. The only thing I can think of right now is to replace the clutch fan again. Perhaps this one is no good.