Hello. My name is XXXXX XXXXX X can assist you. I worked with Clarion as a factory service center. Normally, any of the schemes used by some of the manufactures, to do away with outside vertical antennas, for example GM using a wire in the front windshield, glass have generally failed miserably. They just don't have the gain(amplification) of a normal vertical antenna mounted to the outside, using the metal of the car, as part of the antenna.

That said, the only way to know for sure whether it's the antenna or the radio, is to measure it, through it's 75 ohm antenna input, with an FM generator. I use a Sound Technology 1000A. It should measure less than 1 microvolt of usable sensitivity, at 3% Total Harmonic Distortion. Unfortunately, most shops don't even have this test gear anymore. The main area to suspect of being bad, is called the FM Tuner Pack, which is replaced as an assembly, not a component repair, as most of the work we audio techs do.

I suppose there are a few ways you could test the radio, and or the antenna. One would be to use an RF Modulated CD Changer, which is tied into the car antenna input. An RF Modulated CD Changer, is completely different than a CD changer or satellite radio that use an FM transmitter, within the FCC standards, meaning that the signal is very weak, and is only meant to transmit no further than your own car. The other way you could rule out the antenna, vs the radio, would be to purchase an antenna extension, park 2 cars close enough together, that you could use the antenna in the good vehicle, to try with the radio in this car., or even buy an inexpensive antenna. You don't have to mount it, just ground it to the car. Another way, would be to just temporarily wire another unit into this car, don't bother with the speakers, and see if you can get an FM Stereo indicator to light. If the antenna is bad, not only will the reception be poor, but you will not be able to scan up the band, have it stop on a station, and light the Stereo indicator.

I hope this gives you enough information to rule out the antenna or radio.

Please take a moment, and rate my answer. A rating between 3-5 will insure that I am compensated for my time and experience.

Thank you very much.

Dave