Why solder it when you can slip it over the two prongs.If anything goes wrong the car just reverts to stock.I have been running these for years.
With the resistor in hand, loop both ends of it and slip it over the temp sensor prongs.Then when you connect the plug back on it holds it perfectly in place.
Works great.

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88 300E White, sold 9-04
88 190E Black 2.3 sold
90 300CE White, Grey sold 12-24-04
92 400E White,Grey Sold 5-06
90 300CE 91K Signal Red,Black Sold 2007
1989 300CE Smoke silver,Tan Sold 1-08
1993 300E 3.2 M104 motor
1991 300CE White,Grey
1994 E420 beautiful car,gone to new home
1994 E320 Smoke an Parchment.Beautiful car