I posted earlier about the poor reception of my external gps antenna when placed under the panel by the compass.

UPDATE: on a recent drive I drove for several miles with a partial fix (3 satellites) with the antenna under the dash panel. I lifted the panel and scooted the receiver 5 or 6 inches to the left (by the instrument cluster) but kept it similarly shielded under the windshield bow. The antenna IMMEDIATELY obtained a 3-D fix. It seems as if there may have been some interference while located under the dash panel. ... the compass module was a suggested source.