GGAutobiz: Checking A/C on 1998 Dodge Ram 1500

"The air conditioner isn't working" was the complaint on this older truck. A look under the hood at the visible parts of the system and I could see the clutch cycle switch had been leaking. When refrigerant leaks from a system it not only emits the refrigerant gas but some of the refrigerant oil as well. So if you look for signs of oil seepage you can spot a leak without having to grab a leak detector or black light. In this case the only oil residue was below the cycle switch at the dryer. It looked like a small leak so I expected to find the system with a low charge but not empty. I connected the low pressure side to the recovery machine and did indeed have some refrigerant pressure.

Now with that pressure reading you can tell there is enough refrigerant in the system that the compressor should be able to engage. You can't tell if how much refrigerant is in there. If the system is low and the compressor is engaged then the low side should be lower than you would normally expect to see on a fully charged system. When I turned the A/C on, the low side did go lower than normal and the suction hose was only cooling at 58F. Which was only slightly below room temperature in the shop at the time.

We know the system is low but can't do a proper charge without knowing just how much refrigerant is in there so the next step is to connect the high side as well to the recovery machine and recover the system charge.

The recovered refrigerant is weighed and reported by the recovery machine. A full charge is 2lb, we recovered 1lb 5oz. Also, like with a leak, some oil is recovered along with the refrigerant. The oil is separated into a bottle and measured so you can see how much to add on the charge.