Not sure what this is all really about since I've heard really good things about the main gauge function of the first generation all aluminum body 523. Yes it is all metal so technically it would ground by the hanging hook if you commonly hooked it there (but I haven't) and all the following versions and updates you hear so many problems with are made from plastic but at least for my stuff and all the situations with charging and not being grounded something should have happened to the old 523 but it hasn't. One time that sticks in my memory on my now deadded plastic version 523 was charging one time on a rubber roof and seeing the pressures jump around wacky on the high side that wasn't even connected to pressure. Haven't had anything close to that happen to the old version that still turns on and works. I have held off on upgrading to something like a 570 because of all of this nonsense with the grounding strap, grounding clamps whatever. If I already had a newer testo I would try and fasten a wire down at the manifold and run it up the back to a custom metal hanging hook like I've seen a member here make up after the plastic one kept breaking and make a point of grounding it everywhere including hanging in the truck. Ever get a shock exiting a vehicle? With the lack of problems with the old testo and Digi-Cool with this issue makes me believe the issue is not the lack of grounding but a lack of ruggedness of the electronic components which will be a loosing battle for you and this issue.