So I have a trip coming up today and like an idiot I can't leave anything alone. The AC has been a little weak so I hooked up my manifold gauges last night. The compressor was clicking off on the low pressure cutout at 21psi as the compressor ran, then when the pressure would build up it would come back on. Figuring that was a clear sign it was low, I started adding refrigerant. I was not using a scale, like an idiot, and don't know how much I added but it was not much. The outside temperature was about 68-70 degrees (phone said 70, car outside temp said 68) so I was aiming for about 30-32 psi with the compressor running steadily. It started running steadily but pressure was still down around 25psi. So I kept adding and before it got to 30 psi steady state, the radiator fan kicked on super high and the compressor started short cycling.
Now, it seems obvious to me that I overfilled it. However, it never even got close to the steady 30psi I thought was a minimum at around 68-70 degrees. Is it overfilled? What's the story with it not wanting to reach 30 psi? Any ideas? Should I just pull some out and see what happens?
I had verified between my manifold set and a cheapie "quick fill" gauge that it was around 21psi before I added anything. I didn't double check my gauge accuracy after adding, but it seems like one pressure agreeing between two gauges makes it pretty safe to rely on just the manifold's accuracy.
Bump? I’m going to pull some refrigerant out and see if it helps but I’d really like to know what I did wrong. We leave for the trip in just a few hours and I’d really like to have ac for the trip.
How were/are your high side pressures?
Well last night they were around 150psi when the compressor was running. Today I had trouble hooking up and unfortunately sprayed refrigerant all over. Just trying to get the high side hooked up lowered the charge enough that the compressor runs consistently and the low side pressure is around 42psi at 87 ambient. That seems low to me but at least it’s in operating range and the ac is running. Good enough for the trip at least and I’ll pick this up again when I’m not in a rush.
Vigo
UltimaDork
7/13/18 3:11 p.m.
Well, need to know pressure on both sides when you get back to it. Some cars have sensors that others don't. If you have a low pressure cutout AND some kind of evaporator temp sensor then it's possible that before the low pressure switch was disengaging the compressor before the evaporator could get too cold. Then, you got it to run continuously at ~25psi and the evaporator was freezing, so the system was cutting out from the evap temp sensor. I don't know for sure that that's what was happening, but it's a possibility.
Had this happen to me when I was recharging with only the low side pressure (high side fitting on my gauge set was leaking). Compressor short cycling and the radiator fan on high were my symptoms as well. Find a way to get some of the refrigerant out and the next time you charge it, watch the temperature at the vents. Walmart sells a cheap digital meat thermometer in the cookware section that reads to 10ths. When the vent temperature stops dropping and the compressor starts cycling - stop. Otherwise, charging with just low side pressure is flying blind.
