I have just been browsing around TM/M3W and have spotted someone complaining about dodgy indicator timeouts. One of the suggestions made was that the battery could be either flat or past its best. His battery was 6 years old. As the battery weakens, its internal resistance increases, and so the back EMF of the starter motor will have more effect on the 12V rail. It wouldn't surprise me if an old battery can give 42V or more on a poor battery thus killing the 24V-rated chip in the TSM.
I hope to be able to apply 42V to any pin of the new TSM, but a thought has just occurred to me that the new TSM could measure the battery voltage and report the over-voltage by flashing the dashboard's Hazard indicator. Perhaps 12 very brief flashes then one half-second flash for every volt above 12? Then you could know the state of the battery.
Since this theory could apply to virtually every vehicle on the road, I'm somewhat sceptical the magnitude and duration of such back emf could do damage, irrespective of battery state. An easy way to check though would be a reverse biased LED indicator since most have polarity protection. Such can certainly display the back emf from a small (non diode) 12 volt relay coil with a brief flash, and over a 60 foot cable run as I found out when snagging a warning light issue on remotely operated lamp on my narrowboat.
Richard
2018 Roadster 3.7 1966 Land Rover S2a 88 2024 Royal Enfield Guerrilla 450 1945 Guzzi Airone
