Engine noise (tried almost everything) please help!

[Jack Crow]

Guys,
Wow that was a marathon.

Ive had a couple of wonderful noise makers in GM cars.

My least favorite was the electric fuel pump in the damm tank.

Any time that ran, it threw a buzz into most audio electronics from the factory stereo, and the two way radios.

No joy to change either.

The second was the resistance heater that was the rear window defroster.

One day my two way radios just quit, and the FM entertainment set was only able to pick up local stations. Somethign was clearing knocking the heck out of my RF front ends.

Took a while to find, but the control module that ran the rear defroster failed in the 'on mode'. When current runs across the resistor paste on the glass, it acts like a wide band noise jammer.

A miserable thing.

Either way, Im glad it's solved. Lesson learned.

Be safe
Jack Crow in Kuwait

[DigitalJunkie]

The rear defogger? really?
Maybe the controller was a PWM type deal?

I once had a heck of a time with noise in a car audio setup..took me weeks to figure out it was from the "dimmer module" for the lights in the dashboard/gauges/etc...It was some kind of PWM setup,and was noisy as heck!!

[Jack Crow]

DJ,
Let's look at the physics of all this.

When a current flows through a resistor made of particles, it makes a series of very small arc's.

Each arc is a tiny wide band rf source. Put a few million of these micro arcs in the space of the rear glass in a Buick. It made quite a racket.

Early microwave jammers were spark gaps in resonent containers.

Something to be said for the method.

The relay in the control module latched shut, and that's why the defroster turned on. I found it when I removed the battery cable and drew a fat spark.

Later dude
Jack Crow in Kuwait

[silver00spike]

for some reason, I can lose most of my noise when the rear defroster is off

[Jack Crow]

Silver,
Me thinks your on the way to results.

First off, in this business you can't trust anything other than your self.

Ive just had a major run around with a set of generator controlers because the manuals lie.

Had to work up my own test tools and procedures. Guess what, my way works and refuses to fail.

So the same deal with our cars.

On my old Buick, the control box said the rear defroster was off, light was out.

Yet the welded contacts in the control relay made the indicator lie. The indicator was tied into the defroster timer, not the output circuit.

The unit was passing current like crazy into the resistor grid. When the key was in and turned on.

So if your defroster is off, and the noise went away, that's a pointer in the right direction.

Unfortunatly there is no easy way to solve this short of scraping the resistance heater and installing a blower motor combination. Then your trading one noise for another.

Good luck dude
Jack Crow
TDY Camp Arifjan, Kuwait