I have a 98 24v Couple weeks ago started to act weird lost grid heaters. when you turn truck off the "recently installed" aftermarket radio turns back on, or sometimes there is a clicking sound coming from under drivers side of dash. checked all wire connections look to be good.so today I replaced the ignition switch still the same, and now the turn signals work with keys out of it. any ideas? thanks

 

Sounds like some power is backfeeding thru the radio and back into the fuse panel. Possibly the 12V constant and the 12v switched wires touching on the radio? Is it just the radio and turn signals that work with ignition off?

 

By far I've found most electrical problems to be owner induced.
Go back and recheck your new stereo wiring, maybe even totally disconnect it and see what happens.