I just bought the Magellan Roadmate 760 gps car nav. system. It is sitting in a 1999 Oldsmobile Sihouette, and does not work. The unit works fine out of the car, but inside, nothing. Are there any other units that might work without an external antenna, or am I pretty much stuck with buying one? I think there is something funky about the windshields, because my EZ Pass doesn’t work through the glass either.
You probably have a metalized windshield, which makes a great RF shield.
It’s definitely the winshield.
I have a 2001 Pontiac Montana (same van, badging’s really the only difference, stupid GM), and I’ve found I can’t place my GPS on my dash.
I generally put it somewhere that has reception, like a side window or back seat. (I use a Garmin eTrex that’s usually plugged in to something like a PDA or laptop, so I don’t normally have to be looking at the gps unit, so I can place it pretty much anywhere.)
I don’t know if the Roadmate 760 has a removable/relocatable antenna. If it does, try placing the antenna somewhere else, as the winshield is the only window that’ll actually block the signal. If not, try attaching it to the driver’s door. I know mine gets reception if I place it there (though it’s not the most reliable position)
If you’re willing to spend a little money (though I doubt you’re eager to, as those units are pretty expensive on their own), I see plenty of Roadmate 760 compatible external antennas on eBay, all seem to be going for ~$23 USD plus shipping, which seems to be a decent price (to order an OEM unit looks to be about $55) You could jut throw one of those on the roof and route the cable to the unit, which’ll pretty much guarantee perfect reception.
GPS is strictly line-of-sight, and is thus very sensitive to anything, including windshields, in its way (for this reason, I consider the use of GPS to track sex offenders preposterous; cover it up, no reception).