Assuming the Disco II passes its inspection later today and I can get the fan working again (ballast resistor / regulator already replaced, fan quit again a few days later, but I have a used spare on ready to go in), I will need to recharge the A/C. It was working okay, not brilliantly, but okay, and wasn't leaking AFAIK, but then I had to disconnect the hoses to the compressor to get the driver's side exhaust manifold off to repair that, so now I need to recharge, and I presume purge, and I presume replace the moisture filter / trap thing too.

Is this all a DIY-able on-the-driveway thing or do I need to go to an A/C shop? If the former, can anyone give me the Sesame Street version of how to go about it?

I live on the northwest side of Houston (Cypress - Barker Cypress at 290) so if anyone can recommend a shop that would be great.

Thanks.

 

You need a shop to vacuum the system down. Otherwise its not going to work very well.

 

Our last exchange in your other thread regrettably devolved when you rejected my textbook answer to your question about A/C. I admit I fired the first shot but your response rapidly escalated the matter.

Anyway, one of your arguments was that it has been 95° in Houston with no rain. But it's Houston. Houston. Humiditystan.

I could be wrong and perhaps you'd get lucky doing the job yourself. But even if you reconnect the compressor and install the old or even a new receiver drier "quickly" there will still be air in the system. Air with humidity.

You say you presume you'd need to purge the system. That's correct. YouTube is full of wondrous, creative problem solving ideas and information. I used one to diagnose an exhaust system leak a few weeks ago. Perhaps you can find a way to do it yourself on YouTube or elsewhere. Or maybe someone on this forum knows how to do it.

So let's assume you evacuate the system successfully on your own. You next need to charge the system with the correct amount of refrigerant. The DII spec is 700 grams of R134a, or 900 grams if you have a seven passenger truck like mine with rear air. The correct amount of refrigerant is very important. Too little and the system doesn't cool as it should. Too much and it causes other problems, some severe if it's extremely overcharged. Ask me how I know.

If your truck does not have rear air the 700 grams is equal to 24.7 ounces. Two 12 ounce cans might very well get you close enough. The 900 grams is the equivalent of just under 32 ounces. DIY R134a comes in containers of various sizes so perhaps you could come up with a combination that would total 32 ounces, but again, precision is important. And don't rely upon the crappy little gauges that come with some DIY R134a. If you can find someone with a set of good R134a gauges you could perhaps get close enough.

There have been dozens and dozens of very creative and resourceful members on this and other Rover forums over the eight or so years I've been paying attention and the advice with respect to A/C has always and consistently been that professional equipment is needed.

And I'm curious too about what happened when you disconnected the compressor fittings and released the refrigerant to the atmosphere. If the system was full that might have been quite a show.

BTW it doesn't need to be an A/C shop. Most decent shops have the equipment. And there's nothing Rover-specific about it. Heck, the last time I had it done I had a mobile mechanic come and do it in my driveway. That was great because I didn't need to make an appointment, blah, blah, blah. Much lest hassle. But he had the required equipment, which is the key.

Good luck.

 

What level of vacuum would you recommend I have drawn?

I am curious to know if you looked over your mechanic's shoulder when you had him do your system last time.

Did you observe the sudden "kick" in the pressure gauge indicating that the remaining water in the system that had not been absorbed by the chemicals in the moisture trap had "flashed" over to vapor and was thus being drawn out? I'm curious to know, because the last time I vacuum dried a pipeline, admittedly a 600 mile long, 48 inch diameter one running the length of the North Sea, it took bloody weeks to get the water out that way.

How big was your guy's vacuum pump and what pressure did he get down to? The last test I did drawing a vacuum we used the best vacuum pump at Cranfield University and we could only get down to 10 torr no matter how hard we tried.

Also, how did the mechanic verify he had put in the precise mass of refrigerant called for in the Land Rover specification? Did he weight the containers before and after or did he put the container on a portable scale and measure the mass (weight) drop as he filled it and thus calculate it by subtraction? Was the scale calibrated and did he show you the calibration certificate? Was it in metric units or did you rely on a calculated ounces to grammes conversion factor? If the latter, how many significant figures did you go to in your calculation? What was the plus or minus tolerance you gave the guy on the mass of refrigerant to be added?

How do you cope with car-specific variables like non-precise hose and pipe lengths, compressor dimensional tolerances and whether the sun is shining or not?

Now, in order of importance, I'm off to (a) make sure all my light bulbs are genuine Land Rover ones (because you just know all those ones from AutoZone play havoc with the ECU); (b) to get all the gas station air out of my tires and replaced with official Land Rover canned air (or nitrogen or argon or Kryptonite gas or whatever it is I should be using from the dealership (better have genuine Land Rover tires re-fitted while I'm at it I suppose - and the same goes for the wiper blades, brake pads, spark plugs, windshield washer fluid.... too); and (c) to find a forum where people have half an ounce of common sense.

Ta Ta.

 

As one of the few mechanics on here, I'll answer the questions I can.

760 mmHg of vacuum for 10 minutes to draw the moisture out of the system.
Leave machine on for another 15 to verify it holds vacuum as a leak test.

I am a mechanic. Why would I look over my own shoulder?

No, we generally dont stick around to witness the "kick on the vacuum gauges. Mechanics work on flat rate and 20 minutes standing around looking at a machine is close to an hour of billable work lost.

The machine is about the size of a dishwasher. There are portable units that are smaller. I dont know the specific power of the vacuum pump. But this is what it looks like.




The machine will allow you to input the required amount in grams or ounces.
It is also calibrated (in our shop) once a year when serviced.

Every vehicle has a little sticker in the engine compartment that indicate the amount of refrigerant to be used, including the amount of PAG oil that each vehicle requires for proper system operation. This isn't dictated by the mechanic working on said system, it's from the manufacturer. R&D determines what is required for system operation. I have seen as low as 400g for smaller cars and as high as 1100g for much larger vehicles

Hey, you gotta do what you gotta do.

Based on your previous post, where you were informed what you needed to replace and got pissy, I don't expect a pleasant answer from you.

You catch more flies with honey than with vinegar btw.....

 

you should try DiscoWeb. the guys over there are lot more patient, polite and understanding.