w350 ignition problem help?
 

I have a 1992 w350 when I turn the key to on position the wait to start light doesn't come on so I start it it starts right up but then once it starts the wait to start light flashes on and off for about 20 minutes and overdrive doesn't work once light goes off overdrive works but when light is flashing the grid heater solenoids knock really loud I just put brand new solenoids in it and it didn't help. I would really appreciate help thanks.