Automotive Air Conditioning Information Forum

For an evap, you use the sniffer to sniff the condensate drain hose

If you have multiple pinholes, the gadget will sound off like crazy just about anywhere near the evap

Use compressed air to blow away any lingering 134 to clear out from a cap that was missing, etc, then you know any alarms you get are real

Thanks, that's a great tip, i.e. using the drain line to check the evaporator.

It works because refrigerant is heavier than air

Good news, evaporator hose clean. I am beginning to think I had some leaky tire valves. I did see that they were both filled to the brim with PAG oil. I am surprised to hear that the caps sometimes play a role in sealing. I thought they were like tire caps and were there to keep out dirt and moisture. I bought some A/C valves but they appear to be the same as car tire types.

They are called schrader valve cores.
Using your schrader tool, be sure they are snugged up (do not over tighten)

You MUST have the caps on there for the final sealing, MUST

Cores for tires may look the same, but the sealing material is different I am sure

I am sure you are right about the sealing material on Schrader valves being different for A/C use than tires. But how do you tell the difference? I bought some new valves on E Bay that were said to be for HVAC but how do you know for sure before you invest in all that refrigerant to charge a whole system? It would be nice if they were color coded or? Maybe Tim has some we know for sure are the right ones. I think he has some with matching caps.???

I only know what it says on the package, but buying the correct ones from Tim cannot be a bad idea. Sounds like you are missing caps.
Be aware there are many different thread diameters and pitches to these silly caps.
See if Tim has an assorted kit, because all we can ever do is trial and error by using the kit

Your schrader cores need to be fresh, also, eBay stuff might be old and drying up

If you don't have the core tool, get that from him also
I just bought a compressor from him and it was cheaper than eBay. Ppl do not realize his prices are very competitive

I am not missing caps and have a drawer full of extras. Many fit the threads but I am in doubt about their sealing ability. I guess it's the rubber in the bottom of the cap that does the sealing. Most have a short stem that I wonder about because if that stem contacts the valve at all, presto you have a leak. I will have to check it with the sniffer after charging which I haven't done yet.

This box pretty much covers every core one would need. It might be more than a DIY wants, in that case, match at a local parts store.

43-MT9615

Yea, that's a little much for my needs. My system seems to be holding at 58 pounds on the low side with the gauges still hooked up for two days. I have just 2 cans in the system with the rest being some nitrogen. Seems to be leak free so my trouble before, when I lost everything, must have been the old Schrader valves. The sniffer didn't show anything, neither did the dye test.