I recently purchased a used car. The only problem it had was that the air conditioning did not work – it would only blow warm air. After recharging the A/C system (see that blog post here: mike-thomson.com/blog/?p=1240), I could see that the Schrader valve core on the air conditioning low side port was leaking very badly. This blog post describes how to replace the Schrader valve core without losing your A/C system charge in the process. My car is a 1998 Saturn SL2, but this repair can be used as a reference for most vehicles.
Note: if your vehicle is older than approximately 1994, then it may require R-12 refrigerant instead, and will either need to be serviced by a mechanic or retrofitted with R-134a connections. Do some internet searches to find out more about that.
WARNING! Be careful not to get any loose clothing, hair, or any part of you near the hot or moving parts in the engine bay of your vehicle. Serious injury (or worse!) can happen if you do.
You will need the following items to replace your Schrader valves.
- safety glasses/goggles
- new valve core(s) (Schrader valve)
- low-side valve core remover/installer (if replacing low-side valve)
- high-side valve core remover/installer (if replacing high-side valve)
If you simply remove the valve cores, then your A/C system will completely lose it’s charge and you will probably need to take it somewhere to get evacuated to get the air out. This is why I suggest that you use a valve core remover/installer tools that keep the A/C system from losing its charge. Different vehicles use different sizes of valve cores, so you might need to look around to find the right tool. If your vehicle uses "standard" valve core size (which is like a bicycle tire-sized valve core) like mine does, then you can use these tools:
These remover/installer tools work really well and even include a compartment at the end of the handle to store extra valve cores. Or you can use a kit like this that includes BOTH high and low side tools:
Locating the A/C Low-side and High-side Ports
Your air conditioning system has a low-side port and a high-side port (see picture below). Both are pressurized, but the low-side port is under much lower pressure than the high-side port. The low-side port has the smaller connector (but is connected to the piping that has has the larger diameter). The high-side port is the other one – the larger connector with the smaller-diameter piping. When recharging your air conditioning, only connect the refrigerant can to the low-side port. You can replace the valve cores in either your low-side or high-side ports.
On my vehicle it was obvious that the valve core was leaking because when I had recharged my A/C system using refrigerant that contained dye, afterward the valve was bubbling quite a bit with the bright green dye and letting out the refrigerant that I had just put in (see picture below).
Removing & Replacing the Valve Core
At this point you should put the gloves and goggles on, and then you can replace the valve core(s) as described below. Note that I only needed to replace the low-side valve, but you would follow the exact same steps to replace the high-side valve (except that you would use the tool that is specifically for the high-side port in that case).
- Take a look at the valve core removal tool. You should be familiar with how it works before you start tinkering around with it. The tool has an extractor rod that slides down toward the valve and back up. The end of the rod has a notch and a hole in it that attach to the valve core that your are removing/installing. The tool has a handle on the side that has "closed" and "open" positions. The closed position can only be engaged once the extractor rod has been pulled up beyond the handle’s fixture, thus sealing off the charged A/C line after the valve core has been pulled up. Just below the extractor rod’s handle is a similarly shaped grip area that screws and unscrews from the assembly, allowing you to remove the extracted valve core (after you have closed the blue side handle, of course). You might want to go through the motions first with just the tool so you can become familiar with it.
- Unscrew the low-side (or high-side if that’s what you are fixing) port’s cap. The valve core is inside and keeps the pressure from being released. The cap is just to protect the valve and creates another seal.
- Connect the valve removal tool, but first make sure that you have pulled back the extractor portion and turned the tool’s inner valve to the closed position. Then attach the tool to port by pulling back on the locking ring (which is colored blue in my case), connecting it to the port, and then releasing the locking ring. Since you have the tool’s handle in the "closed" position, no pressure should escape. Remember, the low-side and high-side core removal tools have different sized connectors that match the port you are connecting to.
- Insert the extractor. Turn the tool’s handle to the "open" position, and push the extractor rod down until it contacts the valve core. slowly turn the rod until you are sure that it has aligned correctly and clicked onto the valve core. Push down firmly to make sure that the valve core is stuck to the extractor rod. You really want to make sure that the tip of the valve core is stuck well into the end of the extractor rod that has the notch and hole, otherwise you risk having the valve core fall out while you are trying to extract it – and that would then be a very difficult challenge to overcome.
- Unscrew the old valve core. After the extractor rod is securely connected to the valve core, unscrew the valve core by turning the extractor rod’s handle counter-clockwise. BEFORE YOU DO THIS, you might want to make sure that the extractor rod’s handle is tight. Mine was loose and actually became unscrewed instead of unscrewing the valve core. You will know that the valve core is completely unscrewed because you will start feeling a slight click of the threads when you keep turning the rod after the valve core is free.
- Pull the valve core up with the extractor rod (make sure it is all the way up), and then turn the tool’s blue side handle to the "closed" position.
- Remove the valve core by unscrewing the second grip area that keeps the extractor rod inside.
- The valve core is now out! Notice in the picture how well it was secured to the rod.
- Put the new valve core on the rod. Once again, make sure that the valve core is secured well enough to the rod so that it does not fall out.
- Install the new valve core. Install by doing the reverse of the removal instructions: insert the rod assembly back into the tool and screw on the secondary grip, open the tool’s side handle to the "open" position, push the rod all the way down, and screw in the new valve core. Note that the valve core should screw in relatively easily, similar to how easy it was to unscrew the old valve core.
- Remove the remover/installer tool. Pull the extractor up, and then remove the tool from the A/C port.
- Place the protective cap back on the low-side port.
All done – it is really easy when you have the right tools!