Ac recharge

[DWBOX2000]

When recharging ac on car, am I checking pressure when ac pulley is spinning or not spinning? I get really low pressure(teens) when spinning, when not spinning, ac pressure up to 55psi. I had ac on full blast during testing.
Thanks

[908/930]

I have not done auto AC for some time but the compressor should be spinning. You have the gauge on the return or low pressure side.

[DWBOX2000]

Yes, low pressure side. Thanks

[Bob Kontak]

The on off cycling frequency should reduce or cease as you get closer to the recommended max fill.

[LEAKYSEALS951]

I just did two cars and both are working well, but, I know relatively little about AC, so take this for what it's worth.

Compressor spinning, you will have a low and high side reading. You really want to to have both. (or I do at least)
Compressor off, the high side will drop and the low side will rise until they equalize, sp yes, the low side pressure will actually rise when the compressor is off.

I used a chart like this, and am totally open to tips from people who know more.



Yo' Bob, how frequent is frequent? (I've got one car that blows ice cold, but cycles a lot. If anything, I'm scared I overfilled it)

edit- both cars I did from empty vacuum, and tried to add refrigerant by weight, but ended up needing more than what I thought (weightwise), lost track of weight, so I just used "the force" and went by closest approximation of pressures.

[GH85Carrera]

You really need a gauge on both sides, hi and low.

If it is overcharged, the high and low sides will read too high, like over 300 PSI unless it is really hot there. That chart above is a guide. best practice is start with an empty system, so pull a vacuum, and charge from there.

[DWBOX2000]

I just kept pumping fluid in and it eventually got cold. Thanks everyone.