^^ what he said^^

Yes you absolutely need gauges to accurately diagnose a system. Those BS gauges on those little cans cause more trouble than they are worth. Plus you're only seeing half the story. The high side of the system is just as important to read. Recharging a system isn't like a battery. If you're adding more...it's getting out. Pulling a vacuum on the system is great for pointing out a leaking system. You can rent a pump at Auto zone.

 

I get my AC serviced at a specialized AC shop, and they say the pressure holds over long periods and there are no leaks. I should have mentioned that I live in a hot desert environment, and the AC is on full blast pretty much all the time, especially in the summer. It's quite possible that the refrigerant wears out a little faster with constant usage, but I still think it should be better and last longer.

 

At idle my low pressure is 30, high 235, and revving to 2000 RPMs per a tutorial I watched, low pressure dropped to 25, high stayed the same.

Very strange. I just charged my system with AC Pro refrigerant, and their gauge had showed good. But the gauge also wasn't really changing a whole lot as I charged almost an entire can of AC Pro, only slightly notching up, and it was showing in the 50s.

So I've got something to work with here I guess.

batard, I agree, this can't be normal. I took it to an auto shop and the 57 vent temp was all right they said, but when I called an Auto AC specialist shop, they said they could get it to low 40s. But they refused to even consider working on it when they found it was a Land Rover. Jokes on them though, I wasn't going to use them and was just scrounging some free advice over the phone.

Shiftonthefly1, so I have to evacuate all the refrigerant and pull a vacuum to find and fix a leak, right?

 

Most mineral oil you buy now contains dye. You can use a black Light to detect the dye.

Your high side is a bit low. I usually shoot for low 300's. I'm betting you won't get it too much better with a simple evacuation and recharge. My money is still on the metering device. Also the AC system itself doesn't care if you have it on full blast. It works the same either way. It's the delivery system that regulates air temperature. It's either all the way on or all the way off. It's governed by high and low pressure switches and evap temperature on the metering device.

Again people misunderstand the word "recharge". Refrigerant doesn't "wear out". When you recharge the system you are pressurizing it. Not re-energizing it. If you have some loss of pressure or contamination (hardware breakdown) it's not due to the refrigerant being somehow worn out.

 

Shiftonthefly1, the pressure readings should be gauged based on ambient temperatures, from what I've read, and anything over 300 on the high side would only be acceptable if ambient temperature was over 100. Temperature at reading where I'm at was about 85 in the shade, which puts my high side pressure right in range. Am I missing something?


Got a dye bottle to run through the A/C tonight, we'll see what it turns up. Didn't realize I could just add a little refrigerant with dye without pulling a vacuum. So hopefully some leaks show up.

 

Yea you're right. Ambient temps are a factor too. Forgot about that. It's been 100+ here for 3 weeks. I forget the rest of the world isn't in the same oven we are.

Still...if your low side is getting sucked way down on engine RPM increase, your pressures may be slightly off.

 

Last year I was dissatisfied with the A/C in the middle of a typically hot Carolina summer with temps in the low to mid-90s. I took the truck to my favorite local Rover shop where they'd recently purchased a fancy-schmancy A/C machine that vacs and recharges. They did all they could but with ambient temps in the mid to low-90s about the best I can get at the vents is in the high 50s, measured with an old darkroom thermometer, the kind with a long stem and dial for reading temps in darkroom trays, etc.

 

When I got my truck it was blowing in the mid 50s, so I bought a can of R-134 and, with the engine above idle, I gradually added some until it hit minimum temp, which in in the low 40s. It's still cooling about the same 4 years later.

I can't remember now, but before I charged it I read some technique to roughly identify ideal pressure by ear, or compressor cycling, or something. It worked pretty well whatever it was!

 

Thanks for the input, fellows. Great to hear, dr. mordo, about your good luck with the refrigerant.

I replaced my fuse-blowing condenser fan, condenser with a load of chopped fins from the bad fan, plus a new receiver/drier of course, and filled refrigerant back up. Just drove around with 90 ambient temp, high humidity, and my vent temps are reading 46! We'll see how it keeps tomorrow in the sun, but I'm very excited to actually have significant improvement.

The key, more than anything I found, was pushing my low pressure psi up to 55, which I've read in charts is acceptable to be at for ambient temperatures as low as 85. When the psi was in the 30s earlier today, before I jacked it up some more, my temps were high 50s like they used to be.