I also have a celsius readout and while you would think they would have built in a switch or a terminal change to convert the reading to F, they didn't! Dumb!
Either live with it or get a F readout from a junkyard.

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'76 240D-Sold
'78 240D-Sold
'85 300 SD, 165K-Sold
'88 300 TE, 165K-Sold
'64 Porsche 356C Cabriolet- under restoration
'86 560SL 124K Miles-Sold
'94 320E Wagon, 74K Miles-128K Miles JUNKED
'06 E350 Wagon, 84K Miles
07 SL550, 14K Miles