Sorry I couldn't be more help here, but I expect that MBDoc is sending you down the right trail. He is VERY experienced and if he is suggesting that as the next troubleshooting step it is DEFINITELY worth pursuing.

Do you have a schematic? If not I have not looked in the electrical part of my electronic manual, but I fully expect that I do. I am on a dial up so it might be too large for me to send, but if you need it, PM me and I will try to email it to you.

Good luck,