A/C Gauges read ok - no cold air

[Dan D]

I'm stumped by an A/C problem. Drove the car last Friday A/C worked. Drove it Tuesday A/C didn't.

Here's what I know:

[*]R134a converted last year with a reman compressor, changed oil, blew out lines, new dryer, new exp valve; Vac'd it, charged it - Worked like a champ up till now.

[*]Gauges read (95deg in garage) ~100 psi static. Compressor on = 29psi low side, 235 psi hi side

[*]Compressor engaging and is staying on and pressure differential remains constant above 1500rpms

[*]Condensor fan works - kicks in on A/C button. Changes to high speed when it should.

[*]Blender control changes air from luke warm to hot indicating that it is not stuck routing air through the heater core. (can it get partialy stuck?)

[*]I played with the charge amount, varying the high side pressure from ~180psi up to ~240psi with no change in temp at the vents.
[/list]

What else do I look at?

 

[Lightning1]

I would go straight to the condenser and hit it with a temp gun, if it is good, I would say the blend door. I have seen them stuck halfway like you were saying. It does sound like the ac system is functioning. Another easy check is see if you have water from the condenser, that will tell you if hot air is getting to it.

 

[SouthCaliVR4]

best guess, some critter built a nest in the blend door path & the a/c isn't strong enough to overcome the heater core. if you can evac the a/c @ drop the evaporator core it will give you full access to the whole system. just a few bolts and the a/c lines to get it out.

 

[Barnes]

I've found that you can just grab the lines that run in and out of the evaporator and you can tell if they are getting cold or not. Even a stock engine back should be clear enough in that area to allow you to just reach in there when the engine is running with the A/C on.

 

[Dan D]

There's a little access/gasket panel between the evaporator and heater box. I pulled that off and confirmed the blender is closing/opening properly. I also checked to see if the vent temp changed as the car warmed up. It did not. Also measured the air temp sensor at the outlet of the evaporator. Appeared to be 95-100F based on the chart in the manual. That is the ambient temp today.

Took some temps with an IR:

Inlet of condenser:197F
Outlet of Condensor: 137F
Inlet to Evap (engine bay): 105F
Outlet of Evap (back to compressor): 105F
Vent: 98F

If my pressures read ok, the condenser is cooling some, why isn't the evaporator seeing lower temps?

 

[SouthCaliVR4]

Replace the receiver drier & expansion block. depending on what you find in there you may need to flush the system.

 

[FlyingEagle]

I would have thought the drier too, but it was changed.

 

[Dan D]

So I started this thread a while ago and finally got around to trying some things. I replaced the condensor because the original was questionable. Changed the Exp Valve and drier again and recharged. Same story. Low side pressure of 29psi, high side 150-250 psi depending on the amount I charged it. I watched a temp gauage in the vent as I added more R134a and saw no change in vent temps throughout that 100psi range as it charged. They read a steady 102F (~94 F outside and car was sitting in the sun for a few hours).

I don't get it. How can there be a pressure differential and no cooling?

What the hell do I try now?

 

[thecman02]

Is any line in your AC setup getting cold? My only guess would be a restriction in the line somewhere before the expansion valve.

 

[Hertz]

Swap out the air conditioning controller. ("Auto comp controller") Behind the glovebox, somewhere near the ECU, IIRC.

 

[SouthCaliVR4]

^^^Bolted with two philips head screws right to the front of the A/C box. Just happened to pull all that stuff sat.

 

[mitsuturbo]

I just tossed this stuff in the trash a couple weeks ago. /ubbthreads/images/graemlins/hsugh.gif

 

[Dan D]

Quote:
Is any line in your AC setup getting cold? My only guess would be a restriction in the line somewhere before the expansion valve.



Wouldn't that be evident in the gauge readings on the manifold? I would expect a very low low-side reading and possibly a high side reading that is disproportionally higher for the given static charge pressure. If something upstream of the expansion valve were blocked no. Wouldn't the compressor be pulling suction on it at that point?

 

[Dan D]

Quote:
Swap out the air conditioning controller. ("Auto comp controller")



If the compressor is turning on, can this still be the problem? Judging from the circuit diagram, the comp contoller simply monitors a few sensors and either enables the voltage feeding the compressor clutch relay or disables it. Is there somthing else it does?

 

[Barnes]

I still don't think you have actually tried touching the lines that run in and out of the evaporator. Are they cold??

 

[Dan D]

Warm to the touch when the cars warmed up. IR Thermo says 102 which is pretty close to the temperature measurements I took and posted last summer when it first went out. Since then, I replaced the expansion and condenser and drier

 

[Barnes]

Just so we are on the same page, the evaporator is the part that is inside the car. The lines running to that are 102?? The low pressure line (outlet) at a minimum should be COLD to the touch. Your IR thermometer should be showing something like 40 degrees F.

 

[Dan D]

Yes. Inlet to the evaporator and exit from the evaporator at the firewall coupling block are roughly the same temp.

That is why I'm confused. If there's a pressure drop - there should be a temperature change.