1st Gen "How To" How To Top Up Ac Refrigerant In An R50/53jango

Jango, my 2006 MCS (R53), and I have been driving the streets of Dallas, TX for almost 6 years. I’ve never found the AC to be quite up to the task of dealing with full Texas summers, but until this year, I’ve been able to put up with it. It’s usually only screamingly hot here for 30-40 days in July and August and the AC will at least make the drive to and from work tolerable, though not particularly pleasant during these hottest days. The British and Germans just don’t understand Texas summers.

This year, however, it just went too far. The AC performance had been declining slowly over time so I resigned myself that I’d make an appointment for service and a refrigerant. My brother-in-law reported a bill of over $200 for an evacuation and fill of the AC system on his Jag at Autoscope in Plano, so I thought I’d do a bit of research. I’m sharing what I learned and my DIY process for a MINI AC Recharge here:

A few things that I learned about AC systems and our MINIs:

- All R50 and R53 MINIs use R134a refrigerant. It’s much kinder to the environment than the old R12 stuff and it is legal to buy this yourself at the Auto Parts stores
- There is a ‘high pressure’ and a ‘low pressure’ coolant line for AC systems. It used to be that you had to worry about trying to add refrigerant to the wrong side, but they have solved this problem by making the fittings on the two sides different. If you buy a product like the one I use, below, you won’t be able to add refrigerant to the wrong side.
- The R53 MINI requires 0.91 lb of refrigerant to fill from completely empty (+ or – 0.02lb). This info can be found on a sticker in the engine bay… mine is right up front and center on the radiator fan housing.
- A refrigerant re-charge will fix a problem like mine where the AC is still blowing cool… just not cold. It’s probably the right solution for problems like mine that came on over a long period of time as well… if your AC went from perfect to non-functional in a couple of days, you probably have a more serious issue than a recharge will fix. If you have a coolant leak, the new coolant you put in will leak right out of the system again, so get your leaks fixed by a qualified tech. I know that there are UV dyes you can add to the system and track down leaks with a UV light (also available at auto parts stores), but I don’t know if I’d be able to fix any leak that I might find, so I’d probably take any issue other than a slow decrease in cooling power to a trained AC repair person.
- An instant read thermometer (looks like a thin tent stake with a dial on the top) is handy to use to quantify your actions. I got mine for $7 at an auto parts shop, on the shelf next to the refrigerant.
- Overfilling your AC system is a bad thing. Don’t do it! It isn’t a case where ‘more = better’. They sell cheaper re-charge kits that don’t have a gauge, but don’t trust ‘em… ALWAYS BUY ONE WITH A GAUGE AND USE IT!
- Your target pressure when filling an AC system changes based on the ambient temperature. If it is cool out, you don’t fill to as high a pressure. If it is warm out, you need to go up to a higher pressure. The can of refrigerant had a chart on the side ranging from a target of 25-35psi at 65 degrees outside up to a target of 50-55psi when it is 95 degrees and above. The product I bought had a nifty little bezel that you twist and it would show you the correct target pressure for your ambient temp.
- I saw somewhere that automotive AC systems in good working order can lose up to 10% of the refrigerant per year. That means I might be running on half-power right now!
- A professional will evacuate all of the coolant from your system and will fill it with the correct weight of new refrigerant, collecting the old stuff for recycling. A DIY recharge just tops up the refrigerant, so it might be a good idea to alternate DIY top-ups with professionally done replacements. That will save you a little bit of cash.

Note: I’m not a mechanic, nor have I played one on TV. I have no training other than what I’ve read on-line and on product instructions. I’m just a guy who is handy with his hands and is willing to type up what he has learned to share. Please take all steps you feel necessary to validate what I say for yourself before doing this work on your own car.

OK… So here is what I did:

1. Make a trip to the auto parts store. I purchased a 16oz can of R134a refrigerant and a $7 thermometer at AutoZone. I think that the total bill was $40, including the $5 off sale they were having on the refrigerant. You don’t HAVE to have the thermometer… I just like to be able to quantify what I’m doing and confirm that I got it right. You don’t have to get this brand of refrigerant, but it should say R134a on it and it should have a gauge.

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2. Get yourself ready. Don a pair of safety glasses and gloves. For your neighbor’s sake (if you look like me), a shirt and pants would also be a good idea. If you have the bod for it, consider them optional.

3. Get the car ready. Start the car and open all of the windows. Turn the AC to full cool and turn the fan to high. Make sure that the AC is blowing cool air. You can take a temp reading now by putting the instant read thermometer down into one of the vents. My AC was blowing at 64-66 degrees… cooler than the 90 degrees outside, but still not enough to cool the cabin well.

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4. Remove the cap from the low-pressure service port. You will find this under the bonnet, right near the bonnet release latch (near the front left headlight). There are 2 ports here. You want the one that is closer to the driver. I’ve already taken the cap off of the correct port and I’m pointing to it (the brass fitting). You can see the high-pressure port just above my hand with the black cap on it.

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5. Shake the can. Yes… do it. That’s right… shake it harder… harder! HARDER! Oh yeah! Ok… We can move on now!

6. Attach the can to the port. The valve is a quick connect style with a spring-loaded ring around it. Pull the ring back, push it over the brass fitting and then let the ring snap back into place. Give a good tug on the connector to make sure it is attached firmly. If it pops off, try again, pushing more firmly onto the brass fitting before letting the ring snap back into place.

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7. Look at the pressure gauge. As I mentioned above, the ambient temperature determines your target pressure… it should be at a lower pressure when it is colder out. On the product I bought, the bezel around the gauge turns and moves the plastic face of the gauge. On that face is a high and a low line to show your target range and a short little arrow between them. You point the arrow at the temperature marking on the gauge and then fill up to the high and low marks. It was 90 degrees outside, so I should have a target of 50-55 psi. Mine was at 25psi… definitely low. NOTE: You can only take the reading when your AC compressor is running… make sure that the car is running and that the AC is set to full cold with the fan on high.

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8. If you are low, start by adding refrigerant in 30 second bursts. Fully tighten the valve on the top of the can (holding the can upright) and shake the can back and forth to keep the refrigerant and oil mixed well. When done, loosen the valve completely, remove the connector from the low pressure service port (pull the ring back and then tug on the connector), reattach the connector and then look at the gauge.

9. If you haven’t reached your target pressure, repeat from step 5. I read that it can take up to 10-15 minutes to fully empty a 16oz can of refrigerant. When the can feels empty, you can turn it upside-down to get the last bit of refrigerant out.

10. If you use an entire 16oz can, that is too much for a refill (a full charge is .91lb from completely empty). You may have other problems and you will need to see an AC professional. If you use more than ½ of a can (by weight… just feel the stuff sloshing around in the can) you might want to consult a pro.

11. Replace the service cap on the low-side port when you are done

12. Go check your AC temperature again. After 5 minutes of driving, my AC was blowing at 50 degrees. OK… it’s not blowing frosty air like my wife’s old Cadillac, but it’s better than the 64-66 degrees that it was blowing 10 minutes earlier, so it was a $40 well spent for me.

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Note: I left the thermometer in the AC vent today (August 3rd, 2011) when I went into the office. The weather forecast for Dallas was sunny with a high of 110 degrees. When I went out to my car at 5pm to go home (black asphault parking lot with no shade), the temperature read 130 degrees! YIKES! That’s in a white car with dark tinted windows and a limo-tinted sunroof. I’d hate to know what the temp is in a black car on a day like today. I can tell you that I shift gears by using the leather boot for the first 10 min of driving… no way I’m touching that Whalen shift knob until it cools down!