I have recently add a AEM UEGO wideband to my dash for tuning. This seems to be somehow interfering with the Beltronics RX-75Pro hardwired radar detector. The noise is a very high pitched sound probably in the 15-20k Hz range and is constant.

Initially I thought the bad ground/noise was coming through the cars speakers, so I ordered a noise filter (you know the three wired capacitor). After taking the radio fully out of the dash...which took the better part of 30-40 minutes. Then realizing once I disconnected the radio and the amp under the passenger seat the noise was still there. I hunted around the car and found the small detectors speaker under the dash, the bottom left in this pic. It's maybe the size of a baseball.



So after some irritation I wired the noise filter to the speaker. Didn't solve the problem. I added the actual wires for the detector unit and the speaker, didn't solve the problem. I have it wired in through a 10amp constant fuse under dash with an add-a-fuse. I also have the UEGO wired into the same board (by the driver's left knee) with another add-a-fuse.

^ basically the same add-a-fuse i'm using.

I tried changing grounds up, no fix. i tried running the UEGO ground right to the battery via a wire, no fix. i tried running the speaker direct from the battery for ground and under hood fuse box, no luck there either. I tried running the detector and speaker off different circuits and different grounds, no luck. I tried running the UEGO off different circuits in that panel and different grounds, no luck.



The UEGO is running through the #9 fuse and both radar detector leads were running through #25. I also tried running the radar through #4...didn't work either.

I feel like i've been through every possible permutation to fix this and its just not working...

The ground under dash i'm using is the big steel crossbar that runs the whole length of dash. I've tried grounds for the UEGO all over the car, from under door sill plates, trunk, direct to battery, direct to under hood grounds. I'm out of guesses.

If anyone would be willing to chime in with some ideas on fixing these. I'm all ears...

 

Just wanted to update that I tracked this down after a few weeks. The radar detectors external speaker was actually making the noise, not the car's speaker. Since you only need the amplified speaker in a very loud or convertible car, i simply disconnected it. Problem fixed...after 3 hours on my back and screwing with the wiring...