CB Radio + Noise when depressing brake pedal

Hi TW folks,

I'm working on an issue with my CB radio that's boggling me. I'm getting some interference when the brake pedal is being pressed down and the brake booster goes off. It lets out a screeching sound from the CB and I have to run the squelch all the way up to drown it out.

I tried throwing on some ferrite chokes to dampen the interference but it's still pretty loud. The CB is a uniden 510 XL, Coax is just a no name brand(18'), so maybe a better shielded coax? Power is straight from the battery and runs parallel with the Coax through the firewall port on the driver side. Antenna seems grounded from what I've checked with my multimeter.

Anyone have any ideas?

Thanks!

 

I would try grounding the chassis of the CB somewhere close to the CB.

Unless I misunderstand something, the brake booster is a vacuum device, no electrical connections. I would suspect the brake light wiring is related to your problem.

 

I'll give that a try. The interference only happens intermittently. Maybe 1 in every 4 times I depress the brake pedal.

The CB radio has a ground wire, would this be different?

 

Sometimes the location and length of a ground wire can have strange effects. Also the routing of the power line can be important.

 

There's the ground wire that comes with the CB radio. Both it and the power wire are run straight to my aux fuse panel. Is there a way to better shield the power line against interference? It does go next to the large wire loom through the firewall. The noise seems to go away if I unplug the coax.

 

You might look under the dash and make sure none of the wires are getting crushed by part of the brake pedal mechanism.

 

How long does the coax run parallel to the power wires? This is generally to be avoided.

Which fuse panel and slot did you connect to?

 

Did a check, the cables run clear of everything up and above the brake pedals and the air conditioner lines on the top left corner.

The coax runs parallel to the power inside the cab. I have all the excess cable crammed in the center console section between the drive/passenger footwells. They split off after the firewall inside the engine bay. Power is connected to my aux fuse panel separate from the truck's fuse panel.

If I had a spare coax I would try running a temporary one separately just out the window to see if it made a difference. Maybe it's worth a shot.

 

I would definitely start by putting some space between the power and coax cables, and uncramming the excess coax by just laying it out on the back seat or something.

 

Doesn't seem to fix it. My next go is going to be rerouting all of the cables a new route. Perhaps it's going too close to other power cables that are causing interference

 

@Clam04 sorry to revive an old thread but I’m running into this exact issue and curious if you found a fix.

 

Interesting, I get a little of this in the radio if I’m on AM stations.

 

It was definitely the brake booster on the top right corner causing interference with the CB cable next to it. Sounded like a screaming banshee every few presses of the brake pedal. I'm rerouting the cable to the back of the truck anyhow now.