Radio static caused by blower motor



My 93 Ranger has developed radio static. I discovered it only occurs when the blower motor is running. The higher blower speed I select the louder the static. Am I looking at a motor problem or a control problem? The motor is fine as long as I don’t listen to the radio.


There is an internal arcing inside the motor. I think these motors have brushes that rub against the commutator of the motor. The motor case is usually sealed, so you can’t dissassemble the motor and replace these brushes. You might be able to use a capacitor (condenser) that we used to use when cars had ignition points, or a capacitor that was mounted on generators before the days of alternators to minimize radio interference. The positive side of the capacitor goes to the positive lead going to the motor and the negative side goes to the ground. A .05 microfarad capacitor may be enough to do the trick. These should be available at Radio Shack.

It may be simpler, however, just to replace the motor. It’s probably on its way out anyway.


The problem could be due to excessive commutator arcing as Triedaq suggested. Another possibility that should be checked is the antenna ground or a loose antenna connection. These are common noise inducers also.


I should have thought of this. As Cougar says, check the antenna ground and connection first before doing anything else.


I guess I did get one on you this time Triedaq but you will most likely get me on the next one. I have read some of your replys in other posts and you have excellent suggestions. I can tell by your first reply here that you also dabble in the mystical areas and fine art of the electron.


Thanks for the suggestions, I will try both yours and your competitors. So far I have just listened to FM but I miss my traffic news on AM. Mustangcp2


You didn’t mention in your original post that the static occurs only on AM, but that you don’t have the problem on FM. The AM band is much more prone to interference. Forty years ago and more when generators were used instead of alternators and the automobile was equipped with a radio, there was a filter capacitor mounted on top the generator that would filter out the static noise caused by the brushes arcing on the commutator. The blower motor operates in much the same way. When you are certain that your antenna ground connection is good (the braid in the antenna lead should filter some interference), and the interference continues, then try a filter capacitor between the blower motor lead and the ground. This should be less expensive than a new blower motor. An old time radio and tv repairman may be able to help you out on this.