Audio Systems: audio antenna, sony xplod cd player, antenna connections

Question
factory radio would not switch to fm stuck on am , but received am stations. put in wiring adapter to save factory conectors, installing aftermarket sony xplod cd player, cd plays everything works fine but will not pickup any fm stations . hooked up different radio and it would only pickup 4 stations and not very well.holding the radio in hands helped the reception some, still 4 stations (normal 20 stations.).  Thank you for helping and your time. mike

Answer
You must check the antenna  connections and the fm tuner input area of the tuner section. It is possible the problem is inside the radio unit; if new, take it back for replacement. If not covered by a dealer or warranty you may need to replace it or have it tested/troubleshoot by someone who can dig into the front end.  

You could take of the cover and look inside the area where the antenna connections come in - look for cold solder joint, solder blob or something visible that looks out of place.  If you have no experience with circuits, then better let the professionals do it.

Depending on your car, some have fm preamp built in at the antenna mounting area; bad fuse or rusty connections can prevent the antenna electrics to go sour.  Check that aspect, too.  If you have set in hand, disconnect the car antenna and just put in bare wire of a couple feet long and you should get viable reception - which will tell you if the rf front end of the tuner is good or bad!