Correct A/C steps for filling?
 

This is on my 87 260E, I know you diesel guys have the same A/C setup and most A/C questions are in this subforum...

I am back-converting to r12 FROM r134a as I want r12 performance.

I have a brand new evaporator, expansion valve and R/D. All pipes and condenser have been flushed with a/c flush, the compressor has been cleaned using Ester oil and manually turning and the system is ready to be oiled.

• Compressor 20ml oil
• Condenser no oil
• Hoses: Evap -> Compressor line = 10ml oil, Compressor -> Condenser line = 10ml oil
• Evaporator 40ml oil
• Receiver/Drier 10ml oil

Now the FSM states the system needs 120ml oil. Does this mean TOTAL? Or additional? EG: Once I have oiled up the above places, I evacuate then add 120ml oil + 2.4lbs r12? Or am I wrong?

This is the step I am stuck on and need advice.
Thanks

The system holds 120. If you change just one component (cond due to collision) you "top up" with the specified amount. The oil moves/circulates with the refrigerant so it doesn't really matter that you scatter it all around.

Ok so since all of the above equals 90ml, I need to add 30ml more....Where do I add this then? Just at the low side port with the r12?
All this A/C stuff is brand new to me, so I want to double check everything rather than make a silly mistake that will cost me down the road. My evaporator was leaking this is why I am backconverting as it has been open to the air and needed to be flushed anyway as I had no idea for previous oil.

Thanks for your help.

It doesn't matter where you add it, it all circulates once you start running the compressor anyway. One other note, did you replace the o-ring seals at each pipe joint and use the correct ones for mineral oil? I'm actually unsure if the green rings used for 134a are compatible or not - I know the black ones used for mineral oil/R12 aren't compatible with R134a/PAG oil though.

I replaced the two on the compressor that were black (:confused:) and all the rest were green. So replaced then all with my set I bought. The local shop I took it to for leak testing said he saw a very small leak around the compressor. Maybe that was it as the dealer did not change those seals when converting to r134a (have a dealer sticker for the conversion!)

Thanks for the info. I'll just add the rest to the compressor as it is bone dry.
Onto finishing this evaporator up! Quite a journey....

Thanks!

The easiest way to add oil to a 124 (assuming the system is empty of refrigerant) is to just disconnect the big fitting through the forward firewall. Then pour the oil into the flexible hose and reassemble. As Larry suggests, spin the compressor to move the oil through.

I'd probably just add 3 12 oz cans and call it good. Slightly undercharged is better than slightly overcharged. Most people don't notice any degradation in performance until the system has leaked about half the refrigerant, so 2oz isn't going to make much difference.

A new evap that isn't mostly blocked with years of crud is going to make the most difference in performance.