In Reply to: Not so fast.... posted by Jerry on February 13, 2000 at 19:55:47:
Im pretty sure that when i had the headunit pulled out, but still connected, there was no interference when i hit the rear defroster.
: I've had 2 head units in my M3 and in both cases the only wires that I connected to in the BMW harness were for the amp remote turn-on, constant power, 12v switched and ground. Both head units had a separate wire for the antenna and both times I left them unconnected. Never had problems with radio reception before. So if this amplified atenna module needs to be powered or turned on, how was it being turned on in my case?
: : There is an "antenna" wire that still needs to get 12 volts when the radio is turned to the "ON" position. This antenna wire is actually a turn-on wire for the car's amplified antenna module. This must be powered. If not, the antenna's LNA's (low noise amplifiers) will not amplify the incoming AM/FM signal. When there is no signal lock due to low sensitivety condition (the antenna amp not powered uP) extraneous noise will enter the system, such as the EMI from the rear defroster, etc. connect this wire to either your radio's Antenna output lead or even the remote turn on lead, typically used for external amplifiers.