Yesterday I was with my wife and three children in the car, 300 KM from home just after sunset. I pulled into a gas station and as before all long trips, I dialed 31 PSI on the gas station's air compressor and attached it to the tire. The air compressor was inoperable, and let out enough air to bring the tire down to 26 PSI before I realized which way the air was flowing.

How might I have tested the compressor beforehand?

Simply pushing the "flat inflate" button would not be a good test, as in fact this machine had a few PSI residual and the "flat inflate" button did put out spurts of air. Running "flat inflate" until the compressor comes on won't help as I cannot be certain that 30+ PSI at the sensor translates to 30+ PSI at the outlet (I've had this problem in the past, too).

  • I suppose you could build a gauge setup out of PVC/Iron pipe a pressure gauge and a valve stem. I'd also buy a quality tire pressure gauge if you don't trust the stations gauge.
    – Ben
    Jan 31, 2016 at 16:02
  • @Ben: In theory a double-sided valve stem between my pressure gauge and the compressor would work. In practice, it would be difficult to build one that would hold up to 30+ PSI plus a safety margin, and additionally it would be difficult to hold and use.
    – dotancohen
    Jan 31, 2016 at 16:23
  • PVC pipe is rated to 120psi, if concerned with safety you could add a safety valve. not really that difficult to build one. PVC pipe sealer, a short section of pipe, 2 caps, drill the caps for the gauge and valves.
    – Ben
    Jan 31, 2016 at 16:34
  • 4
    Try it on your spare first (if you have one).
    – HandyHowie
    Jan 31, 2016 at 17:06
  • 1
    @HandyHowie: Post that as an answer! Simple, elegant, requires no special tools, works on all vehicles with no prior preparation.
    – dotancohen
    Feb 1, 2016 at 6:57

1 Answer 1


A simple way to check that the compressor is working would be to try it out on your spare tire first. If you have one.

  • 2
    That might work for a truck with same pressure tires, but many auto spares are high pressure mini-donuts running 60PSI or more.
    – kmarsh
    Feb 1, 2016 at 19:44

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