Had flat battery on Ford Mondeo. Jump leads to Vauxhall Corsa accidentally reversed (brown was neutral!). Only item not working now in Mondeo is radio. Have removed from fascia. Is it diode? Can I (not gifted amateur) fix or do I need to have an expensive expert/new radio?

Ron M, August 2008

Yes, completely dead. There was a hot electrical smell when I first got in the car so the blown theory sounds good. Have not had top off yet, but someone told me about "one way" diode usually fitted at exit from radio which might have protected it if current was reversed. Will check with multimeter for power. Have no back-up ford to test it on. I suspect ebay might be my only answer.
I notice that you have been very helpful to many people on this site, and I would like to express my appreciation for your time and consideration.
RonM

Ron M, August 2008

Is it completely dead? (no display or any noise/hiss from speakers?)
If so , check that the battery feed is OK to the radio.(using a multi-meter or a test lamp) If it is , then I suspect it means that the radio has blown.(you could try fitting it into another Ford or fit a spare Ford radio into yours ...if you have access to one?)
Remove the cover and visually inspect the components inside as quite often it will be an overheated resistor that has blown. There might even be a small fuse fitted inside.

Might be worth buying a replacement off Ebay?

RegWorts, August 2008