Get some LA Totally Awesome cleaner, make a solution with 80% water and soak it overnight. Use a small acid brush on it every hour. It will be spotless afterwards. After it's clean , you'll be able to see where the broken solder joint is. If you project a line straight down from where the wire is still attached, you'll also find where it broke.

I have had broken nichrome wires (at the solder joint) where it's too short to be soldered back on. By splicing/soldering a short pigtail strand of copper wire to the nichrome, I was able to fix and save the sender .

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked