Rene Sauvageau, an FJR1300 rider out of Calgary, Alberta Canada posted the following:
My TPMS sensors on my Garmin 590 have been flaky since new, especially the rear. I tried many things over the years. (spoiler alert, I finally fixed it). Here's what I tried:
* replacement unit
* replacement TPMS sensors
* replaced batteries (many times)
* bought different valve stems both rubber and metal. I now have the Hawk with the dual stem.
* I tried using the vertical and horizontal parts of the valve stems.
* I even tried to move the GPS to a new location on the bike.
But nothing ever fixed it. My rear was so bad that I just unpaired it since the pop up messages were ridiculous. I finally figured it out the other day.
I pulled the main board out of the 590 and found three antenna components on the board. Makes sense since there should be a GPS, Bluetooth, and ANT antenna. Two of those three had nice solder joints, but one had a cold solder joint on one end. The ground plane looks rather large so the heat profile during manufacturing must not be quite right. Anyway, after touching up the solder joint it fixed it. I rode yesterday for 400 KMs and not a single dropout of the TPMS's.
When the Zumo forums existed, there were lots of guys complaining about this exact thing so I assume there are many more like me with this problem. Here are some pics and what I touched up. Its hard to see in the pics, but under a scope you can clearly see the cold solder joint. Hope this helps anyone with a similar problem.
Attached photos of before and after. (no laughing at my solder touch up, my eyes are not what they used to be). I have a small finger on my solder joint, but in my defense lead free is harder to touch up then leaded solder used to be.
