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Old 07-28-2013, 03:06 PM
funola's Avatar
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Originally Posted by JHZR2 View Post
Less is more. 134a is more sensitive to overcharging than r-12, so you really need to be careful and very slow. Use real gauges, watch high and low sides, and use a sensitive digital thermometer to keep watching temps drop. As soon as they gonzo one degree, stop.

Use a giant pusher fan to keep the condenser working at a steady rate.
Less is more? Should I let out the 134 that's in there?

Seriously, I want to get it as cold as possible. I have manifold gauges, I have a digital thermocouple meter for fast response. I just want to do the rest right w/o blowing it up.

I hear the pros on here charge by weight then final by vent temp to get it as cold as possible. So there must be some techniques they use w/o over doing it.

85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
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Old 07-28-2013, 03:35 PM
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Yeah exactly as I said. Dont think that adding extra will do you good, it won't.

Usually on a system with its native refrigerant, one would charge 85 or 90% by mass and then do exactly what I'm saying. Add a little into the system by opening the valve shortly, then watch vent temps, repeat over and over until you see the temp stop dropping and just rise slightly, and/or pressures start to go to an undesirable range.

Remember that you're just filling the receiver dryer, but adding more to overfill and drive pressures up kills efficiency and raises cent temps - thus less is more.

In a retrofit r-12 system, the charge of 134a is around 80% of the r-12 mass, do you probably want to do 85% of 80% and add slowly from there.

Current Diesels:
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