Guys,

I've had an AC issue for the past three years. Here it goes:

Problem: My AC is blowing hot air. When the compressor is engaged I get a high pressure of 425PSI and a low pressure of 50 PSI. With the compressor disengaged the low pressure is 125PSI. One would think I am over charged but the aforementioned pressures are with only one 12oz. can in the system.

What I've tried:

It started with a noise that I suspected to be a clutch bearing. At that point I only had a Haynes manual which stated that the clutches are non serviceable. I replaced the compressor and had a local shop charge the system. The AC system blew barely cold air. It is worth noting that I had a fully functioning AC system outside of the "clutch bearing" noise. I lived with that setup for three years until I couldn't take it anymore. It turns out that the original compressor was from the clutch top plate being warped and rubbing against the pulley during a small portion of one revolution of the pulley.

Last month I bought gauges and found that my system was low. Since I discharged the system and went ahead and replaced the accumulator. The AC blew cold for a while, though at idle speeds it would blow hot air. A few weeks later it started blowing hot air all the time. This past weekend I replaced the orifice tube and the condenser. It still blows hot air.

Here is what is weird: I draw a vacuum to 30 in-Mg for 1 hour, close the valves on the manifold and let is sit overnight. My gauges still read 30 in-Mg in the morning, leading me to believe I have no leaks in the system. I cannot put more than one can of R134A (12oz with a system capacity of 2lb) before I start getting 425PSI high pressure readings.

With the compressor engaged, if I trace the hoses starting at the outlet of the compressor I feel heat on the following: compressor hoses, the inlet of the condenser, the condenser, the condenser outlet, and half of the length of the liquid line/orifice tube. The remaining half of the orifice tube is cold and sweats a little bit the rest of the way up to the inlet of the evaporator. Once the compressor disengages the liquid line/orifice tube changes to hot all the way up to the inlet of the evaporator. When the compressor is engaged the liquid line/orifice tube is quite a bit colder going into the evaporator than it is at the accumulator and the suction hoses to the compressor are. The accumulator feels a little cold, but not nearly as cold as the liquid line/orifice tube.

To me this all points to a clogged evaporator. I will get a Sanden OEM SD7H15 replacement compressor in tomorrow, as the one I threw in it three years ago was some Chinese Autozone POS. I doubt the compressor is it but I have one coming anyway.

Give the novel of information above, do you guys have any idea what might be the issue? I'm fairly new to AC system and have only started to learn about them within the past month. Is it normal for half of the liquid line/orifice tube to be cold and half of it to be so hot you can't touch it? I can feel about a 1" long transition area where it goes from hot to cold?

 

Wow 425 PSI your on the right track with a blockage or a junk compressor. Did you find any debris in the orifice tube/filter when you changed it?
Also good idea to change the receiver drier during the compressor swap.
It is critical in the 134 systems to use the right amount of oil per component changed ie: 2 oz for evap 2 oz for condensor 4oz for compressor etc.(general numbers). Too much oil causes problems.
I would check that orifice tube/filter again.
50 psi is a good low side pressure normally but not proportional with the 425 on the high side it leads me to believe that compressor is junk.
I would take every precaution I could so that if there is trash (desiccant) in the system you don't damage a new high dollar compressor.
Flush the lines with cleaner and re service components with oil.

PS my compressor clutch broke the same way.

 

Would I be able to see any junk in the liquid line? The orifice tube and the filter are internal, and I sure can't see it from either end of the liquid line? I saw online about a guy cutting this in order to see if any crap was trapped in it. I am able to blow through it with shop air and have it come out the other end without noticing any gross blockages.

Why does running at 425 PSI lead you to believe the compressor is junk? It seems to me that the fact that I'm running at 425PSI tells me that the compressor is doing just fine. I am still new to AC stuff so I don't understand it all.

I don't have a receiver/dryer in my setup. Are you referring to the accumulator? I did replace that a few weeks back. When I replaced my compressor a few years ago I ignorantly had the system open to atmosphere for over a week during humid month of July. That triggered me to replace the accumulator last month.

 

Accumulator is another word for receiver dryer. both do the same thing one term is old school.
The reason I believe the compressor may be bad is because if your orifice tube is not clogged and the oil is serviced correctly in the system, the only other thing that separates high side from low side pressure is your compressor.

 

I installed the OEM USA made Sanden compressor in today and it, as I expected, didn't do a thing. I am still seeing 425PSI on the high side and 50PSI on the low side. The only remaining items that haven't been replaced are the evaporator and the suction/discharge hoses. What gets me the most is how I can only get one 12oz. can of R134A in before I start seeing the high side pressure get way too high. Even if I hook another can up and open up the suction side of the manifold it won't draw any more freon out of the second can. At this point its possibly a collapsed suction hose or an almost completely blocked evaporator.

 

I replaced the suction/liquid line and, in line with everything else in the past, nothing changed. The liquid line/orifice tube frosted over for the second half of the length of the tube. Meanwhile the outlet of the evaporator leading into the accumulator is room temperature. It has to be the evaporator. Can anyone comment on half of the accumulator frosting over while the other half is hot?

 

There is a restriction in the accumulator.
If it is frosting it is changing pressure from high to low. and that's the orifice valves job .
Did you blow air through all your lines when you had it apart last time.
Make sure it is installed in the right direction and blow through it with 50 or 60 psi.
I think you found your problem.

 

After replacing every component in the AC system I finally figured out the issue. I was told by a machine repairman at work to spray water with a hose on the condenser and see if the pressures on the manifold gages drop. Sure enough the 425PSI pressure almost immediately dropped to 100PSI. I was then able to charge the system with the proper 2lb of R134A. The air was blowing ice cold as long as I sprayed a moderate amount of water in the condenser. This led me to believe I had a failed fan clutch. I installed a new one but it was unable to keep the condenser cool enough at idle. When I am driving the air hitting the condenser is enough to keep it cool. If I stop for more than 20 seconds the pressure gets so high that the over pressure valve on the back of the compressor engages for a few seconds and I can see freon gas escape from underneath the hood. At stoplights I turn off the AC. I turn it back on when I am moving again.

I must have a clogged radiator or intercooler. At highway speeds my engine gets above the standard 190F. It doesn't overheat, and doesn't go over 190F, even at a stoplight on a 95F day.

What a boondoggle! The radiator fan was spinning at what seemed a reasonable speed, but it apparently wasn't enough.

 

Change the accumulator! blow through the condenser lines while you have the accumulator off.

 

I forgot to mention that I did replace the accumulator and condenser lines as my last step before finding out I had a bad fan clutch. Replacing both changed nothing.