I have a 75 Sundowner and last year installed a 430 gps and a 340 audio panel. Included in this up grade was a new encoder and new wiring to all head phone jacks. Since then I have had problems with my mode C reporting several hundred feet off sometime high sometimes low and 70% of the time it is close enough. I have brought it back to the radio shop 3 times now and each time they can't find any thing wrong in the system but repalce the encoder anyway. Anyone else had a simlar problem?

Ron Cribbie