Bear with me on this as it may be a little confusing. Roughly a year ago, I replaced the OEM radio with a Kenwood digital unit. Bought the proper aftermarket harness and the Euro anntena adapter, made all the connections, and all was good. I didn't install the secondary harness to retain the SWC at the time, mainly due to time and cost, but plan on doing so in the future. At this point, everything was perfect, no problem with sound, reception, all of the USB ports worked, etc.. About 4 months ago, I decided it was time to add some bass to the car. I bought a 10" shallow-mount sub because I have a 500c and very limited room in the trunk. I spent a decent amount of time configuring a box that would fit on the left side (like the JB Audio version) and meet the needed cu ft requirement for the sub. Also bought a Class D mono amp to drive the sub. Box built, amp connected and the entire unit installed in the car. However, after a few weeks, I started noticing the FM reception was declining on various stations. Double-checked all the wring and connections and all was as it should be but 1 shop suggested that having the amp tapped into the ANT Power could be drawing just enough amps to weaken the signal. So I moved the amps remote power wire to the charging port on the center console. The amp needs to be connected to a non-continual power source or else it will drain the battery even with the car turned off. This change had no affect on the reception. Fast-forward to about 2 weeks ago and I noticed that only 1 local station will stay in at all times. All other stations are either intermittant or simply don't tune in at all. Once again, out with the HU, check the wiring, etc. and all is good. I read online that Kenwood has a history of the blue/white wire (marked P. CONT/ANT.CONT) not providing 12v which obviously will affect reception and I read that Class D amps can also affect reception but usually when installed on a motorcycle, not a car. I have spoken to a few local radio install shops and also with Crutchfield's support and no one seems to have any idea what is causing this. Also, I had removed the entire sub box and amp for about a week as I built a new, smaller box and during that time, the reception was still bad. This eliminates the idea that the amp is causing the interference which only leaves the radio itself or something with the cars antenna. I am at a loss as to the cause of this and am hoping someone on here will have a suggestion that I have overlooked.
The radio is connected as folows:
blue/white wire from radio (P.CONT/ANT.CONT) to blue wire from the antenna adapter
blue/white wire from aftermarket harness to radio blue/white wire (P.CONT/ANT.CONT)
blue amp remote turn-on wire connected to 12v power plug in center console
Also, with the car running and the radio powered on, I disconnected each blue/white wire. Upon doing so, almost all of the sound would then be routed through the subwoofer; highs, lows, vocals. The only way it worked properly was when all 3 wires were connected together. I tried each possible combination and got the same result.
Any ideas would be appreciated.
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Originally Posted by 5port
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