2000 Grand - Re-Charging Air Conditioner Success
The air conditioning on my 2000 Grand Cherokee limited has been performing less and less well over the last couple of years. Besides not cooling the cabin well enough, with the air conditioner turned on the engine idle was cycling back and forth between 600 and 1000 RPMs, and the air compressor clutch was disengaging every 20 seconds or so. Today I read up here on this forum and in the service manual and decided that the likely cause was insufficient R134 coolant in the A/C system. Went to the local auto supply store and picked up a can of refrigerant for $8 and a simple fill kit with pressure gauge for $16. I noted there are lots of recharge kits that include oil or leak detector in the coolant - since I was just topping off I got pure R134. Came home, hooked up the new pressure gauge to the low pressure port near the back passenger side of the engine compartment, ran the engine at 1,300 RPMs as called for in the service manual and saw the pressure was at 15 PSI. Aha I thought - the manual says it should be around 30 PSI given it's 65 degrees outside. Hooked up the can of refrigerant and made mistake number one. The compressor clutch cycled off and the pressure on the gauge rose from 20 PSI to 75. I got nervous - I didn't know whether the can of refrigerant could handle 75 PSI and didn't want an explosion while holding it in my hand so I unscrewed it. I then learned the can has no valve as the contents of the whole can gushed out - so blame global warming on me. Back to the service manual I learned that if the compressor is cycling you need to short out the wiring harness connected to the compressor clutch switch, which is attached to the black cylindrical refrigerant tank next to the low pressure port. Shorting the wires prevents the compressor from stopping. So a quick trip back to the auto parts store for a new can of R134, find a 4 inch piece of wire to short out the compressor clutch harness, run the engine at 1,300 RPMs and voila - I hooked the gauge to the low pressure port, screwed in the can of coolant, set the can upright and it took about 15 minutes for the can of refrigerant to slowly bring the system up to 30 PSI. Lo and behold once this was done it was freezing cold in the cabin of the jeep, and above about 25 PSI my engine idle stabilized at 600 RPMs.
Answer:
does this mean that the proper psi reading is shown only when the compressor is running? because when I was filling my ac unit, the pressure would drop when the compressor was running so I thought that the true pressure reading was when it wasn't active .... am i wrong on this? Is the true psi reading shown when the compressor is running and is that psi the one you should be following when recharging the system?