C5 radio buzz when IP lights on
Thread Starter
Instructor
Joined: Apr 2002
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From: Annandale NJ
C5 radio buzz when IP lights on
I get an annoying buzz on FM stations on the lower half of the band whenever the instrument panel is lit. The dealer has replaced almost everything in the system - head unit twice - all with no effect. I tried a few other C5's both new and used on the dealer's lot and they all seemed to exhibit the same symptom to varying degrees. Is there a cure for this (other than replacing the whole system) or is it something that "comes with the territory"? :sad:
Melting Slicks
Joined: Sep 2000
Posts: 2,756
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From: Satellite Beach, FL, USA
Re: C5 radio buzz when IP lights on (mbtc5vette)
The C5 uses Pulse Width Modulation, PWM, to vary the brightness of bulbs in the dash. This technique can generate harmonics that would extend into the AM and FM band.
ALL modern cars generate "hash" that jams certain AM or FM frequencies. Unfortunately, it is a byproduct of modern "digital" circuits used in todays cars. Usually, the interference does not jam a useful radio station.
I am not saying, this is your problem, but it could be.
As a "sleeze" fix, you could put small capacitors to ground, .01uf, across the outputs of the BCM feeding the bulbs in the dash. The capacitors will slow down the rise time of the PWM signal, thus limiting it's harmonic content. You need to look at a service manual to see what BCM outputs to put the caps across.
ALL modern cars generate "hash" that jams certain AM or FM frequencies. Unfortunately, it is a byproduct of modern "digital" circuits used in todays cars. Usually, the interference does not jam a useful radio station.
I am not saying, this is your problem, but it could be.
As a "sleeze" fix, you could put small capacitors to ground, .01uf, across the outputs of the BCM feeding the bulbs in the dash. The capacitors will slow down the rise time of the PWM signal, thus limiting it's harmonic content. You need to look at a service manual to see what BCM outputs to put the caps across.
Team Owner
Joined: Mar 2001
Posts: 54,124
Likes: 30
From: Cincinnati, Oh USA
Re: C5 radio buzz when IP lights on (mbtc5vette)
I feel for you because here is where the designers didn't do their jobs right! Now unless they provided a fix (dealer should be able to find this out) it will be up to you or someone who understands how to suppress EMI (electromagnetic interference) to stop it. Try calling the area GM customer relations person and explaining the annoying problem you have.
Thread Starter
Instructor
Joined: Apr 2002
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From: Annandale NJ
Re: C5 radio buzz when IP lights on (jfb)
I only posted the question here after I gave up on GM and the dealer solving it. I went back and forth with both of them for months about it. As I said, virtually everything in the whole audio system was replaced -head unit, Bose amp, antenna stuff, speakers, all grounds were checked, etc.. The head unit was replaced twice because the first replacement was worse than the original one. The dealer also went back and forth with GM Tech support on it and I called the Chevy hotline several times (waste of time - just said "see dealer"). I think it's one of those "they all do that" problems since I tested a number of new and used Vettes at the dealer and they all showed the symptom to varying degrees. I thought maybe a Z06 with the fixed antenna might be better but it did the same thing. I think I'm more susceptible to the problem because I live in a radio "fringe area" about 60 miles from both NYC and Philly, so I'm getting a weaker signal. The problem pretty much goes away when I drive into the city. But it's still aggravating because I've lived in the area for 16+ years and never had any such problems with any other car radio. :nonod:
Melting Slicks
Joined: Sep 2000
Posts: 2,756
Likes: 5
From: Satellite Beach, FL, USA
Re: C5 radio buzz when IP lights on (mbtc5vette)
Welcome to the world of digital electronics.
Modern radios cannot compete with older high peformance analog radios because they actually jam themselves with internally generated hash. The other huge problem is the hash generated by all the other electronic modules in the car itself.
You could try using a cheap handheld radio and "sniff" out the module that generates the most hash. The more sophisticated methods would require some expensive test equipment.
Modern radios cannot compete with older high peformance analog radios because they actually jam themselves with internally generated hash. The other huge problem is the hash generated by all the other electronic modules in the car itself.
You could try using a cheap handheld radio and "sniff" out the module that generates the most hash. The more sophisticated methods would require some expensive test equipment.
Advanced
Joined: May 2002
Posts: 65
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From: Vinemont Al
We can start a Bose sucks club if you like! This may not apply to a C-5 at all but I will tell you on an 89 there is a relay under the dash that makes the radio buzz and pop when it is bad. It makes you wonder why they would place a relay in a place where you have to take the dash pad completely out and move a move a lot more stuff and have tiny hands to get to.
I guess you already know of all the speaker amp buzzing and popping problems on these. I had to redo all of mine and then dig for that relay. That fixed that.
Somebody at Bose has kissed the right asses at GM. Their systems suck and are expensive to fix.
This probably won't help you but I feel a lot better!!
I guess you already know of all the speaker amp buzzing and popping problems on these. I had to redo all of mine and then dig for that relay. That fixed that.
Somebody at Bose has kissed the right asses at GM. Their systems suck and are expensive to fix.
This probably won't help you but I feel a lot better!!
