Electrical Interference on a diesel....Problem?

[jcd]

One thing I love about my diesel is that there is no ignition or any other electrical interference on the radio. The only time I would hear any interference is when I would use the turn signal or I would hear a little, very little pop when I applied the brakes............until tonight.

I picked up interference on the radio tonight, at low RPM's, disappears at higher RPM. The interference moves up and down with RPM changes, most noticable when the transmission downshifts. It stops abruptly when I apply the brakes and then resumes when I let off the brake pedal.

Am I losing my mind......

JCD

[240Joe]

It's probably electrical interference generated by the alternator. It might be going away when you activate the brake lights because the current flow changes the regulator turnon point.

You might need to check the capacitor on the alternator to see if it is still good, or add another one.

Do you still have a decent antenna? If you lose enough signal to the radio because of a poor antenna, the radio automatic gain control (AGC) circuits crank up the RF gain to compensate. This will also amplify RF interference picked up by the radio.

So also check the antenna.

Joe

Sorry for the long answer...it's the ham radio operator in me.

[Palangi]

Static electricity buildup from the tires rotating. When you step on the brakes you are providing a slightly better path to discharge the buildup to ground. There are grounding clips in the front hubs to reduce this problem. As a quick test, try dragging a short chain from the chassis to ground (Like the old time fuel trucks used to have). If that eliminates the static, it pretty much shows tire static to be the cause. My Taurus does this on weak signal AM stations.

de WC5P

Just as a sidenote, I took off the grounding clips from my 300D after finding one broken off in the grease. Didn't want to have one get chewed up and get in the wheel bearings.

[Palangi]

I looked this up in "The Radio Amateur's Handbook"

They refer to wheel noise and tire static as two distinct problems.

Here's what they have to say:

"Wheel noise produces a ragged-sounding pulse in the mobile receiver. This condition can be cured by installing static-collector springs between the spindle bolt of the wheel and the grease retaining cap. Insert springs of this kind are available at automotive supply stores."

"Tire static has a ragged sound too, and can be detected when driving on hard-surfaced highways. If the noise does not appear when driving on dirt roadsit will a sure indication that tire static exists. This problem can be resolved by putting antistatic powder inside each tire. This substance is available at auto stores, and comes supplied with an injector tool and instructions."

This verbage is found in The Radio Amateurs Handbook dating at least as far back as the early '50s. I have heard of this anti static powder before, but have never actually seen it in any auto supply store. There are references in some editions from the '50s to Chevrolet as a source for the described anti static powder, but I would be surprised if that were still true. Nowdays with VHF FM being the predominant automotive radio mode, noise issues like these are pretty much a moot point.

I found by accident that if I turn on my headlights that the buzz on weak stations goes away. Also my cell phone charger will increase the noise level with weak AM stations. Give it a try.

[84300DT]

how about drenching the tires with water and then trying it while running
(yes i've done this and it does work...