Save Your Money
Mine doesn't work correctly on my 300E either. It shows either 5 or 6 degrees in C I suppose. I didn't see anywhere that it can be changed from F to C so I'll let it be. The outside temp really seems irrelevent to me, it's either a light coat, heavy coat or a no coat day, and by the time you get in the car it's too late anyways. You'll need to make a trip back to the house to get the coat. I'd spend my hard earned money on things that make a difference on the cars performance first and leave the cheap temp gage and sender they installed alone.
"Tell me and I will listen, Teach me and I will learn, Show me and I will accomplish, Involve me and I will succeed."
'84 300SD 256,000 Gold on Brown (Mileage Award)
'86 300E 246,000 Blue on Tan