Oxygen Pressure Gauge

[Top Heavy]

The Oxygen pressure gauge on my Mooney Bravo reads a constant "0" despite the fact that the tank is fully charged and there is flow through the cabin outlets. This occurred immediately after the broken Oxygen control cable was replaced. The mechanic says that the gauge needs to be replaced. Assuming that the gauge is truly defective as opposed to a kink or some other misadventure during the process of replacing the cable which runs near the high pressure tubing to the gauge, does anyone have any  leads as to where to find reasonably priced replacement gauge? Also, will it be necessary to empty the tank before removing the defective gauge or is there a valve to interrupt the flow in the high pressure tubing prior to replacement? Do you have to use sealant tape over the threads and if so, given the fact that it is an Oxygen fitting, what type of sealant tape? Thanks for any advice.

[kortopates]

I responded on MAPAlist as to why I agreed with your mechanic on it being the gauge. Even a pinch in the line isn't going to block 1800+ psi of pressure from getting to the gauge.

I suggest checking with salvage yards for a replacement. I have not looked up the park number but I suspect it will be the same gauge used in the same O2 Mooney systems used in many of the models K, M, R & TN and therefore not bravo specific and thus a bit easier to find.  

No, you will not need to drain the tank to replace the gauge. Your mechanic will simply disconnect the HP line from the regulator on the tank. A HP needle valve on the regulator will prevent the air from escaping the tank (just like a bicycle tube stem valve). Yes, their is a mil standard teflon tape specific for O2 applications that is reference in the Mooney service manual. My recollection is that the standard has been superseded by a newer one, but you'll find with a little searching its commonly available - even on amazon. But there is also a small o-ring that goes on the end of the HP line that inserts into the O2 regulator that should be replaced when the line is opened up. That can be found in your mooney IPC (illustrated parts catalog).  In fact, searching on MS you'll find I cited the O-ring part # on another thread about O2 leaks for a K model;  but best to verify what your IPC says.

[Top Heavy]

Thanks for the information. It is exactly what I needed to know.

[SkepticalJohn]

19 hours ago, Top Heavy said:

Thanks for the information. It is exactly what I needed to know.

I have an extra O2 gauge from recently upgrading my system. I'm out of town for work currently but would be willing to ship it to you when I get back home in a few days. Try it out, if it works we'll figure out what it's worth. If it doesn't work, you'll know there's a problem elsewhere and you can ship my gauge back.