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Ac recharge

Justin Fleming

Justin Fleming

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all new ac components, compressor, condenser, evaporator etc. I put 3lbs R134 in the system and I can only seem to get the duck vents to blow at about 50. The compressor is cycling on and off consistently. It seem that the low side cycles from 30 to 50ish psi. It acts if its low on Freon but like I said I have 3lbs in it. should the compressor be cycling or should it be staying on the entire time? Any thoughts or ideas?

The weather in Michigan is 40 degrees and rainy right now. Not the ideal time to be tuning an AC system but components failed so I am fixing them.

thanks
 
How long did you draw the vacuum before charging? In cold temps you need a really long time and good vacuum. It might help to run the engine to get things warm underhood.

But you're charged now, so hopefully the vac was fine. What does the sticker say? I've heard 44oz, which would imply you're overcharged at 3lbs. What kind of oil are you using?
 
Did you swap out the R12 pressure switch to a R123a pressure switch?
 
clandr1 said:
Did you swap out the R12 pressure switch to a R123a pressure switch?
Click to expand...

Pulled vaccum for 1 1/2 hrs, and it sat over night with zero leaks in a heated gargae.

Did not swap out the pressure switch, was not aware I needed to do that.

The system had already been converted by someone in its previous days

I was told for R12 the system took 3.3lbs and 134 swap starting point is 90% of R12 amount.
 
The factory pressure switch is adjustable, so no need to replace it. I prefer the ability to tweak it anyway. Some systems can handle lower pressure than others.

What are the high side pressures while all this is happening? It's probably hard to see an overcharge that way in the cold temps, though.
 
I just thought of something else. Are you sure the blend door is blocking the heater core off fully? You might check if the vent temps rise from a cold start. When you think about it, this may be the only explanation for vent temps ABOVE ambient with A/C on.

At 30 or 40 degrees ambient, the compressor may cycle a lot since there's so little load. With so many new parts and being an R134 conversion, I don't think you can calculate the ideal charge exactly - you probably have to find it experimentally.

Are you getting cold pipe all after the evap outlet? It if frost all the way back to the compressor you probably have enough charge.
 
Blend door is moving as it should

The high side gauge is only around 120 - 130

The system has a fresh 8oz of Ester oil
 
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