I’m having trouble with my 2002 civic AC, and the issue is low pressure. After jumping the low pressure switch, the AC kicked in. When I shut down the car, there was a hiss coming from the blue low pressure line dust cap.

I had some work done on the AC last summer, and I’m assuming that the Schrader valve loosened, or possibly failed (not sure what the chance of that is). When I depress the Schrader valve, there is pressure in the line, just not enough to engage the AC I figure.

Would it make sense to try and tighten the low pressure line Schrader valve, and charge the AC with a kit?

From what I’ve read, you should charge (using a Red Tek kit) the AC when the AC is running. In my case, the AC doesn’t run because of the low pressure, so should I jumper the low pressure switch?

I’ve also read that low pressure when the AC is running should be max 40 psi. Is that true for a 2002 civic as well? Is there somewhere that I could confirm the specs? i.e. service manual?

Thanks in advance, I would appreciate some help.

 

Tighten the valve and get a new plastic cap. Shrader valves almost always leak a little, the plastic cap is critical to keep the refrigerant in.

Don't use a kit with one gauge Most of those kits have additives in the can that you don't want. The only things present in your system should be R-134a, PAG oil, and UV dye. Absolutely don't charge any leak stop or "high mileage" crap. Buy a professional-type gauge manifold with two gauges and a couple of cans of plain R-134a.

At this point you can consider your system empty (it only has a few oz) and charge to the weight specified on the sticker. Do not jump the switch. After you start charging, the pressure will rise enough that the compressor will start. Pressure when running is not so important as knowing the correct amount by weight is in the system. It's always best to start empty and charge by weight rather than try to "top off" looking at pressures.

If you don't see yellow-green leak detection dye in the service ports already, use a can of 134a with UV dye as the first can. This will make it easier to find leaks in the future. Look around for other leaks, everyone thinks that their service port is the leak but it's typically something else.

 

If all or nearly all of the refrigerant has leaked from the system, air/water may have entered the system. Therefore, it may be wise to have the system evacuated prior to recharging it with refrigerant/leak detecting dye.

 

Thanks for the info. I did see some green-yellow dye on the dust cap.

If I am charging the system, and there are pressure guages on the kit, is there a maximum pressure that I wouldn't want to exceed while filling with the system running?

 

As a gross rule of thumb, high side should stay below 2.5 x the ambient temperature in Fahrenheit. In other words don't let it get into the 300's of psi. If you don't overfill, and the condenser fan works, this should not happen. The low side doesn't mean much, at least as far as being sure not to blow anything up. I agree with Ron if you have a vacuum pump use it and evacuate to be sure there's no air. Also then you will be starting from zero so you can charge exactly the weight on the specification sticker.