My ac quit blowing cold today. It has worked ok up until today. I can hear the compressor trying to kick in, but it immediately turns off when it does.

My confession is I added refrigerant to it yesterday with one of the DIY tools that are really not a good idea, but I only pressed the trigger for a max of 15 seconds and it never got near even the low end of the recommended pressure on the gauge. It blew nice and cold last night and this morning, but I had a nice hot ride home from work today.

So where should I start? renting a real manifold gauge and checking the pressures? What should the high and low sides read?

Would it act like this if the ac clutch coil went out? I have had a whirring sound when the A/C is on that changes with RPM, but it's done that for years and so I haven't been too concerned about it.

Every time I've had A/C issues with the Cooper, it was the coil was burnt out in the compressor. I've swapped it out three times now. Not too terrible of a repair. Hardest part is removing and reinstalling the snap rings.

Normal pressures should read 35 psi for the low side and around 200 for the high side. I would check these pressures first before doing any type of repair.

Check that you haven't added too much refrigerant. R53s are a bit picky about the level of freon they want in the system. Too much and the compressor will kick on and off as you describe. You can get a nice manifold gauge set at a reasonable price from Harbor Freight. If you are doing any other repairs or if the system was left open for a while you may want to consider pulling a vacuum on it to remove any moisture as well.

Good luck!

So it turns out that I did over fill it, not by much, but enough. When I hooked the manifold gauges up, my high side pressure was at 300psi and the low side was at 70psi. I disconnected the gauges, bled the hoses out, and checked the pressure again. Just losing the amount of refrigerant in the hoses dropped the high side pressure to 225psi and low side to 40psi, and now it blows nice and cold.