Ex ambo A/C R134a charge weight

Hello,
Can anybody help me with the correct R134a charge weight to re-gas my A/C.
Ex ambo 2001 316 cab chassis (cabin only, no rear A/C) with the non factory A/C system typical in the ambo's

The reason I need to know is I'm looking into replacing the gas with the more efficient HR12 hydrocarbon type refrigerants which
use only 30-40% of the original charge weight.

Thanks, Iggy

I've got hr12 in mine. I disconnected the rear ambo Ac in mine, but since it was shared with the front system, the placard under the bonnet (saying 2.0kg) was then useless because half the system was gone.

So I just filled it, while looking at temps and pressures. As soon as evaporator temp started increasing after dropping and holding for quite a while, I stopped. It took around 350g of HR12 in my case. But I have a double thickness condenser due to the shared setup it had.

If yours is "crisp air" branded, they are in qld and they even showed up on this forum a year or so ago offering spare parts etc. The parts aren't cheap. But they may be able to help as long as you haven't modified their setup like I have.

Decided to charge with HR12 using the 30psi low side pressure reading method as I couldn't find the correct weight for the R134a.

WOW what a difference, really cold air & now I can't tell if the A/C is on or off in regards to engine performance so definitely more efficient