I've had my Disco about a week now. Today it finally warmed up to 65 degrees here in central VA, so I tried system in both auto and economy modes. Auto, at 60 degree setting, didn't seem to get very cool. I had the windows open, so perhaps the system was having trouble establishing ambient temp. Maybe I need a recharge. What puzzled me more, though, was that in economy mode (just vents), the air seemed pretty warm. Is that symptomatic of these trucks? With the engine running pretty warm, and the outside air presumably running through the engine compartment somewhere, I could see this happening. Any thoughts?

DRW

 

Auto mode will cycle the a/c on and off as needed to cool the air, if you have the windows open it wont know what to do.

In economy mode all you are doing is pulling in outside air, the air inlet for the cabin is under the windshield, open the hood and at the base of the windshield is the opening.
So yes, if you are in traffic or driving slow it will suck in hot air from the engine.

 

Thanks. I'll experiment with it a bit more!

 

Economy mode does that man. I pushed it on accident a long time ago and thought something was f'ged up but it was really me being a klutz.

 

Oh yes, if mine's in econ, it pumps out hot air when it's warm out. Gotta love that!

 

buy a pressure guage and hook it up to your low side service port on the a/c line. most come with a temperature range window and little guide book on what kind of psi you should see as the compressor cycles.

ac systems are completely closed, and never need "recharge". if the pressures low, the compressor might be on its way out, but 99% of the time, you simple have a leak, usually the orings on the lines, less often, maybe damage or rust through of the lines somewhere or components. "recharging" might help short term, but gets rather expensive... if you plan to keep the car, better repairing the leaks then dumping more and more r134 at it thats just going to leak out.

run some ac UV dye, open the hook one night with the ac on max with a uv flashlight, and find the leak... might get lucky and its just rotted seals, find a garage with a recovery system to save you the cost of refilling new after a purge.

 

That is entirely incorrect. There is a reason that the hoses in an AC system are called "barrier hoses", and that's because they aren't totally impermeable. Properly functioning systems absolutely will leak, but have a sufficient buffer of refrigerant that most people don't notice for about 10 years until it gets to the point where its short cycling and not cooling well.

This is why non azeotropic blends are such a bad idea (popular R-12 "replacements"). The components have different boiling points, so they permeate the hoses at different rates, making a full evac and recharge the only way to get a proper mixture back into the system.

 

Thanks for the great thoughts and discussion. I posted elsewhere that I received the diagnostic code P1536, which seems to be associated with the AC system (I say seems to be, as an Internet search also suggests this code has something to do with the emergency brake). Any additional insight will be greatly appreciated!

DRW

 

That would be the evaporator temperature sensor. If you are having A/C issues, it's entirely possible that it is working properly, and telling the CCU that the evaporator coils are icing over. Its there to turn off the compressor to make that stop happening. BUT, I would say its more likely that this is the cause of your AC issues and not a symptom. It's not all that uncommon for one of those to fail.

Get it unplugged and put an ohm meter on it. If it's 0 ohms, it's spanked - get a new one. As a test, you can bridge the terminals with a 1.8 ohm or so resistor. This should tell the ECU that things are good enough to let the compressor run. Listen for it to turn on, and feel if you are getting any cold air. Also listen for "short cycling" (the compressor turning on and off every few seconds) - that tells you you are low on refrigerant or have other systems problems.