A/c

I don't know enough about A/C systems to know any better about this... hopefully someone can enlighten me here...

I recently recharged my A/C... with engine and compressor running I charged it to about 35psi. Fine... no problem with that...

I happened to put the pressure tester on when the engine was off and it wsa reading over 100psi!

WTF?

I thought something was wrong so I checked on another car and it was similar... why is the pressure higher when the engine is off? I assumed it would be higher when the compressor is running...

So... I don't think anything is wrong... just curious what is going on.

When the compressor isn't turning the high and low sides equalize. It's the high pressure side that goes to the condenser in front of the radiator. The low side goes to the evaporator inside the car. I think when the AC is off the low side which is normally cold returns to the pressure of R-134 at room temperature which is (as you said) around 100 psi.

Thanks... I don't know if ou are right or not, but that works for me! :)

Yep that is correct, You have to be care full just using low side gauge although. If the high side gets over 300 you will start to blow things!