Ever since I bought the TR6 the temperature gauge has read way to the left, only rarely in the solid white. It was running really rich when I bought it, and I thought that was the problem together with potentially a bad sender. I finally fixed the running rich problem, and the gauge was still way to the left.
I was reading some threads on www.britishcarforum.com on bad senders, etc., and ran across someone mentioning to also check for a stuck open thermostat. I removed the thermostat cover, and – no thermostat at all. Previous owner….. grrr….. Ok, I’ll get another thermostat.
But nothing is as simple as that. On Moss Motors site there are multiple choices. First is temperature range – one for winter, one for summer. Second is failsafe or not. I’d never heard of Failsafe, but looked it up, and if they fail, they fail open, so coolant keeps flowing. I decided to spend the extra 6 or 7 dollars and get a failsafe at the OEM recommended 180 degrees. Autozone carried it and the gasket, had it in stock, saved me a couple buck and the shipping fee.. Part Number: 7200-180
The bolts holding down the thermostat housing were rusty. I cleaned them up with a wire wheel on a dremel tool, and used anti-seize on the threads. I also cleaned the mating surfaces of the housing really well before reassembling. I did not use gasket sealer.
The results? The temperature gauge now runs about the middle of the white zone, and guess what? The heater now works! I have driven in high 20’s low 30’s weather, and it was COLD. And my wife will now ride with me in the winter!