I recently purchased a Pioneer DEH-1500 car stereo and am having problems
getting an FM stereo signal out of the unit, even when stations are coming
in loud and clear (in mono) with no noticable static. Only a select few of
the most powerful stations come through in full stereo, but even those will
very readily drop to mono when the antenna is moved even a small amount.
Switching the LOC setting on and off seems to have no effect, and I'm about
20 miles from the nearest broadcast tower so interference shouldn't be a
problem anyways.

Have tried two different antenna cables, both are perfectly fine. Nothing
wrong with the jack in the unit itself that I can detect either (without
opening it up). For antennas, I have used:
1) Just the antenna cables, no antenna attached
2) The car's antenna
3) A dipole antenna (indoors)
4) The roof antenna (indoors)

Naturally, the roof antenna yielded the best results, but the stereo kept
insisting on only providing stereo for a few stations, even with a very
large number of them coming in clearly in mono.

I called Pioneer and they suggested that the unit needs to be serviced, but
I don't want to find out that this is just how the unit works and have spent
more money on servicing than I did for the stereo in the first place.

Does anyone out there, possibly with a service manual and in-depth
understanding of the Supertuner IIID, know of a way that I could make the FM
tuner a bit more cooperative? I'm more than willing to open the unit up and
modify what's necessary given the right information. Also, if anybody else
here has a DEH-1500 I'd like to know if they are experiencing similar
problems. Thanks ahead for the help. :-)

Greg F.