Duracool?

[Mikeyman]

Has anybody recharged an older AC unit with Duracool 12a? I've used it in the truck and it was a simple job and works well. Any experience or advice would be great.

[idroba]

Duracool 12a is similar to R12 in pressures and performance. Most rooftop AC units use R22, and R12 is not a replacement. If it does use R12, you need to have access ports to install it, and it is quite tricky to regulate the amount. It takes very little R12a to fill a system and it is quite hard to measure accurately. An automotive system has a bit more tolerance for refrigerant amount, but sealed systems such as rooftop RV's have are quite critical.

What makes you think you need more refrigerant in your rooftop AC refrigerant unit to begin with? They seldom leak, as they are factory sealed and welded shut.

[Mikeyman]

Fired up the AC for the first time in 15 years, and the compressor ran for a second and kicked off. My truck did the same thing when it needed a recharge. The PO said it was working 15 years ago... And with the freezing and cooling from winter to summer 'round these parts, it isn't uncommon to have "winter loss". Which lead me to thinking maybe I could service the thing myself.

[idroba]

The rooftop AC is a sealed system and in general does not have any leakage, even after 15 years. It is not like an open system in a car or truck which has rotating seals and rubber hoses connecting things that leak over time.

The auto AC units have a low pressure switch on them which may allow the compressor to run momentarily until the switch shuts off, indicating lack of refrigerant. The sealed rooftop AC units have no such switch.

After 15 years of no use, the first thing I would consider checking is the start and run capacitors, and the relays associated with them, not the refrigerant level.

Rooftop AC units and automotive AC units have similar parts such as fans, compressors and condenser and evaporator coils, but operate and are serviced differently.