Calling All A/C Gurus -- HELLLLLLLLLLLLPPPPPPPPPP!!!!!!!!

[70_F100]

While I've been working on my project, I decided to finally fix the factory A/C.

The bolt on the crankshaft of the compressor had somehow loosened and let the clutch slip some and wore the taper so it was unusable.

Here's what I've done:

1) Replaced the compressor with a used one (York 210). I pulled the head and valve plate. Absolutely no wear on the cylinders, pistons looked good. Pulled the valves from the valve plate and checked to make sure there was no rust or corrosion, reassembled valve plate and reassembled compressor using new gaskets. Pulled the bottom plate, cleaned compressor crankcase well with A/C flush solvent, reassembled and filled to the proper level with Ester oil. Checked to make sure there was pressure and suction on the corresponding ports. Re-installed compressor and fittings with new o-rings.

2) Replaced the expansion valve with a NOS expansion valve. Insulated the valve and lines with the proper "gummy" tape.

3) Started to replace the receiver-drier, and when I took the inlet fitting to the drier loose, it pulled the threads off the fitting to the condenser. Went to the local pull-a-part, tried to remove the drier on two different trucks, same thing. Result -- bought a new condenser from American Condenser. The new condenser was a direct bolt-in, but it's a parallel-flow instead of serpentine like the original. Installed new receiver-drier.

4) While the lines were disconnected, I blew through them in both directions with compressed air. No restrictions. Also blew through the evaporator, no restrictions.

5) Evacuated the system with a good vacuum pump for about 45 minutes. Checked for leakage after about 10 minutes, let the system sit for about 15 minutes, held steady at 28 in Hg.

6) Recharged the system with 24 oz. R-134a and 2 oz. oil charge. (From what I’ve read, it should take about 80% of the system capacity when converting from R-12 to R-134a, plus, American Condenser said that the new condenser would require a little less refrigerant than the original) 24 oz is approximately 80% of the original charge capacity.

Now, I have hot lines from the compressor through the condenser and drier, all the way to the expansion valve. Lines are cold from the expansion valve through the evaporator and back to the compressor. All feels good.

Here’s the problem (engine running about 1500 RPM, ambient temp approximately 90 degrees, doors and windows closed, fan on high):

1) Outlet air temp is approximately 68 degrees.

2) Suction pressure approximately 6 psi. Discharge pressure approximately 230 psi.

3) Adding more refrigerant makes the discharge pressure increase, but the suction pressure remains about constant. Outlet air temp remains constant.

4) Heater hoses are cool, so there’s no heat being added through the heater core.

5) All control cables are adjusted properly.

The questions:

1) Why won’t my suction pressure increase? (I’m pretty sure it should be between 25 and 40 psi) Tried another expansion valve, that didn’t change anything.

2) Is this as cold as my air is going to get, given that the system was designed to run R-12? I remember working on these systems in the past and getting 35-40 degree discharge air.

Any help/advice would be GREATLY appreciated!!!

[flyboy2610]

Result -- bought a new condenser from American Condenser. The new condenser was a direct bolt-in, but it's a parallel-flow instead of serpentine like the original. Installed new receiver-drier.

R-134a does not cool as efficiently as R-12. You need to increase the condenser capacity. Translation: you need a bigger condensor designed for R-134a. You may not have enough refrigerant in the system.

[70_F100]

Thanks, Flyboy.

I bought the only condenser I could find that is a bolt-in replacement. The engineer at ACI told me that, even though the capacity is a bit less (only an ounce or two less than the original), the parallel flow (with about twice as many horizontal runs) vs serpentine design would provide at least the same amount of heat transfer (and possibly more) as the original. Of course, we all know about sales pitches, so you might be dead on the money.

As for refrigerant, adding more did absolutely nothing until I got to the point that I KNEW it was overfilled, then the discharge pressure went WAY too high.

I'm pretty sure one thing that's hampering the cooling is the fact that the suction pressure is so low, like there's a restriction in the system somewhere. The condenser, though, as you suggested, could also be at least part of the problem. I just don't think that's all of it (but I've been wrong before!!!).

Any other thoughts, anybody????

[fordman]

i have always thought 134a wasnt as good as 12 myself. the rest i cant help with. i know nothing.

[70_F100]

Thanks, fordman.

Yeah, that's what I've always been told, that it doesn't provide the cooling like R-12.

That's sort of why I was wondering if I'm getting all of the cooling I'm going to get with it.

[flyboy2610]

http://www.acsource.net/acforum/viewfor ... 0a99ce533d
You might try here. Seems like an active forum.

[basketcase0302]

If you add refrigerant and the discharge goes up but not the suction, a couple of things you might want to check:
1) Airflow, is the evap coil clean with no leaf or other debris blocking the airflow? Does the airflow seem good? Does the fan seem to be up to speed?
2) The TXV could not be opening all the way, (do you have an infared or thermocouple type tool to measure the evap line temp where it leaves the pleunum area). You should see a decrease in that temp when you add the gas.
3) Could be the suction valve in the compressor is sticking (not taking the refrigerant).
4) If the condenser were too small, you might want to try and add some forced air (box fan) or other fan to see it it will decrease the evap temp. Not a permanent repair-but rather a diagnosis.

Hope it helps!

[70_F100]

http://www.acsource.net/acforum/viewfor ... 0a99ce533d
You might try here. Seems like an active forum.

Thanks for the link, flyboy. I’ll check that out and see if I can get some more info there.

1) Airflow, is the evap coil clean with no leaf or other debris blocking the airflow? Does the airflow seem good? Does the fan seem to be up to speed?

Jeff, I pulled the underdash unit a couple of years ago to replace the blower motor, and I cleaned out everything, including the plenum inside the kick panel. The airflow is excellent (actually, almost too much when the blower is running on high speed). I actually got a degree or two cooler temp by running the fan on medium speed.

2) The TXV could not be opening all the way, (do you have an infrared or thermocouple type tool to measure the evap line temp where it leaves the plenum area). You should see a decrease in that temp when you add the gas.

Yes, I checked all of that with an infrared thermometer. The temp of the evaporator and lines is within 2-3 degrees from the TXV all the way through the evaporator and the low-pressure line leaving the unit. I stuck an A/C thermometer through the louvers on the case into the coils/fins to double-check that the IR was correct.

3) Could be the suction valve in the compressor is sticking (not taking the refrigerant).

It’s taking refrigerant fine. Like I stated, I pulled the valve plate and checked the valves and plate before I installed the compressor. That being said, I didn’t pull the pistons from the compressor, so I guess if the rings were bad, it might not have enough compression to properly open the suction valve.

4) If the condenser were too small, you might want to try and add some forced air (box fan) or other fan to see if it will decrease the evap temp. Not a permanent repair-but rather a diagnosis.

I did put a box fan in front of the condenser, and that didn’t make any change. There seems to be plenty of airflow across the condenser with just the engine fan. In fact, even driving it didn’t make any noticeable difference.

Update:

I looked in the LMC catalog, and they list a condenser for the factory air. The drawing doesn’t really give a good visual of it, but from what little I could tell, it looks identical to the one I installed. I could see that it had a round vertical tube on the passenger side, which leads me to believe it’s the same parallel-flow unit I purchased.

With that in mind, I called LMC and asked if they would check to see who manufactures the one they sell. They told me they would check and get back to me. If it’s the same one, I have to assume that it’s working well for their customers, or they wouldn’t continue to sell it.

I’ll keep working with it, and I’ll post any updates when I have them.

Thanks, everybody, for your excellent suggestions!!!

Richard

[basketcase0302]

Richard,

The symptons almost sound like non-condensibles (moisture) but don't seem likely due to your description of the service procedure you performed. New drier/evacuation/held evacuation seems hard to believe there would be any moisture there.

I'd suggest getting a sub-cooling temperature reading on it next, (this will rule out a few more things like moisture and also tell you if the TXV is opening as designed). I'm sorry but I can't explain the procedure for obtaining the sub-cooling here. Maybe the above link will describe sub-cooling measurements in detail?

Hope it helps.