REPLACING A SCHRADER
By: Brian Curry <email@example.com>
There are a number of digital tire pressure gauges out there. They are neat units. They appear to be fairly accurate. They display to 1/2 psi. Press a button to energize them and they display the pressure for a bit after the reading stabilizes.
However, they are battery powered. And if I have had the batteries die in one, I am sure that others have too. The units are not designed for "user service." However, they cost ~US$16.00 and "a dollar here, a dollar there, pretty soon you are talking real money..." The worst that would happen, if I took it apart, would be that I would have to purchase a new one, and that is what they wanted me to do. The cost for a new battery set is ~US$4-5.00, much less than a new gauge. If it worked, I would be well ahead of the game. :):)
So, here is how I took my Schrader gauge apart and replaced the battery. The methods and results may also apply to other digital tire pressure gauges:
There is a narrow split along the length of, and around the case. The threaded head connection is part of the case front, so don't worry about cracking it. Using a thin flat screwdriver blade that fits in the split, put it in the split near the measurement port and twist. Not too much. Just enough to get the case to separate a bit with a "cracking" sound. Move the screwdriver blade along and repeat. Continue all around the case. The back will separate from the front where the ON button and display are.
This will scrunch up the plastic where you twisted the screwdriver. So I used a knife to shave the high points, pushed up by the screwdriver blade, off. Don't cut yourself! ;);)
With the case split, you can see that the case appears to have been solvent welded together. It was not designed to be separated again. (But it can be...) The batteries live in the back of the case and are connected in series. There is a padded connector behind them. One of the printed circuit board battery connection points has a "+" on it. The positive battery terminal contacts this point.
You need two (2) 3 volt Lithium CR-2032 cells to replace the installed units. The Radio Shack part number is 23-162. Take one of the old batteries when you go to the battery store. There are a number of batteries, all about the same size, that look "very similar".
Pop/pry/lift the old batteries out. I tried simply putting the new batteries in the old batteries location, and I could not get a good connection to the circuit board. So, I put a bit of aluminum foil (folded to about 4 thicknesses) on top of the padded connector. Now everything worked fine. :):) So, install the batteries, one with the "+" up and one with the unmarked "-" side up. Confirm, that the positive "+" battery connection will touch the "+" marked printed circuit board pad.
Since the batteries are not held in place, and can fall out, I held the back, batteries facing up and then put the top/face of the gauge on top of them. When you press the ON button, check that display shows "0.0" for a little bit. This shows all is well. :):)
I didn't glue it back together again. I might have to change the batteries again. I taped it back together again. I put one and a half wraps of vinyl electric tape around the gauge just to the left/below the display. Another wrap went around the body next to where the measurement head screws on for a total of two. Pull these tightly, stretching the tape a bit and you will not have funny ripples in it.
You now have a pressure gauge ready to go again, for about the one third the cost of a new one.
Brian Curry, 1990 Blue K75RTs both coasts, Chester Springs, PA, USA
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