QuestionQUESTION: I just read the question from 4/30/09 regarding failing speakers and the TSB from Chevy. Mine is an '05. Here's the breakdown of this week.
Monday morning and at lunch I had one speaker working (front right). Little sound from front left. Nothing from the rears.
Monday night on the way to dropping it off, all four work
Tuesday morning at the Chevy place they only had one working again, but when he plugged in a new speaker, it worked. I witnessed this and marvelled.
I told them to do nothing else.
Tuesday night I go to get the car and all four speakers are working.
Tuesday night I put in a new battery and all four speakers are still working – I have a theory that the issue is a weak battery causing the radio to function oddly. I know that my battery was weak so I was doing this anyway.
Wednesday morning I go to work and only the front right is working again.
So the battery thing didn’t fix it.
But it is either one speaker or four, nothing in between.
I'm thinking along the temperature line since it doesn't work in the morning (65 degrees) but is after it sits in the sun all day (90 degrees)
ANSWER: Hi John,
I've never really gotten any more details about the Trailblazer TSB (although I would have expected the Chevrolet dealer to be able to access that information).
In a case like yours, where you have three separate speakers that are failing all together, it seems pretty clear that the ultimate culprit is the head unit (or, if you have a Bose audio system, the factory amplifier). It's highly unlikely that three of your speakers would have a defect that affects all of them at exactly the same time. Given the temperature connection, it certainly seems that the issue is the same one detailed in the TSB; but without knowing the details of the bulletin, I can't really tell you much more. If the dealership wasn't aware of the technical bulletin when they checked your system before, you might want to contact them again and see if they can look it up.
If it comes to that, it's certainly possible to replace your factory head unit with an after-market one. If you decide to follow that route, I can give you more information about your options there. However, if your problems are related to the Trailblazer TSB as we suspect, your best course is to continue working with the dealership.
Good luck!
Brian
---------- FOLLOW-UP ----------
QUESTION: OK, so we have a little more detail. While driving at lunch today the front left came on, but not the rears. Then, after a two-hour afternoon meeting I got in the car and the rears worked also. This tells me that there is not a common point of failure. Could it be that the speakers are failing, but work better when warmer? There's no evidence of water entry in the doors.
Oh, and I spoke to the dealership. Gave them the TSB and NHTSA numbers and it didn't do anything for them. I even sent them the link to Edmonds which they've seen. They aren't showing anything on the speaker/temperature issue in their system.
ANSWER: Hi John,
Unfortunately, this is a problem which I probably won't be able to figure out unless I have a vehicle in front of me to do some testing.
I'm doubtful that the speakers are the source of the problem, because a speaker is really such a simple device. It's just a coil of wire placed near a magnet. If AC current is passed through the coil, it will be alternately attracted to and repelled from the magnet, which is what makes the cone move. If there's current flowing, then the speaker will be moving; if there's no current, there's no movement. A defective speaker usually has a break in the wire, so no current can flow through it. But you don't generally get an intermittent break in the wire inside the speaker, let alone one that's related to temperature in any way. And a break in the wire is really the only thing that can prevent a speaker from producing sound.
Another possibility is that there's an intermittent poor connection at the speaker plug. However, the exact same plug design has been used in just about every GM vehicle since the early 90's, so I'm skeptical that it's causing a problem in the Trailblazer.
If I had the vehicle to troubleshoot, I'd use a digital multimeter with an AC voltage function. I'd take the dash, door, and kick panels apart so that I had access to the wiring in the radio harness, the harness going into the doors, and the terminals at the speaker itself. If I had a speaker that wasn't playing, I'd start by testing for AC voltage at the speaker wires in the radio harness. The voltage on a speaker wire should increase and decrease with the volume of the audio signal. (I have a meter with a bar graph display, which makes this very easy to see; I also have clips on my test leads that let me test a wire without disconnecting or stripping it. An analog meter would also work, because you can watch the needle move in time to the music; but you have to be absolutely sure you're testing a speaker wire, as analog meters can trigger air bags if you test the wrong wire).
If no AC voltage is found on the speaker wires behind the head unit, then it's clear that the head unit has a problem. If there is AC voltage in the radio harness wires, then I'd test for voltage directly at the speaker terminals: voltage there, with no sound output from the speaker, would definitely indicate a problem in the speaker. Finally, if AC voltage is found at the head unit but not at the speaker, then there's clearly a break in the wire between the two. I could do more testing at various points along the wire (especially on both sides of the speaker plug, and at the wire bundle where it runs out of the cabin into the door) to try locating the bad connection, or I could just run new speaker wiring from the head unit directly to each problem speaker.
If the head unit isn't the problem, then I'm guessing that there's some connector in the vehicle that contains all or most of the speaker wires, and it's intermittently coming apart. Temperature changes can make materials expand and contract, so that might explain why the problems seem to be related to temperature. However, without having a vehicle to test, it's all guesswork on my part.
If you want to try to do some testing on your own, here are the wire colors associated with the speakers:
Left front: tan (+) and gray (-)
Right front: light green (+) and dark green (-)
Left rear: dark brown (+) and yellow (-)
Right rear: dark blue (+) and light blue (-)
The speaker wire pairs are typically found tightly wound together as they run through the vehicle cabin; so if you see a brown and yellow wire, interlaced and running up into the driver's side B-pillar, you've probably found the left rear speaker wire on its way into the door.
I hope this helps!
Brian
---------- FOLLOW-UP ----------
QUESTION: OK, so I went the easy route. I bought new speakers. Not from GM (heavens no) and put them in last night. The all four worked last night and all day today.
Do I have every confidence that I addressed the root cause - nope. But I'm happy with a speaker upgrade and if it winds up being the head unit, I'll be happy to get a new one of those also that's a little better than the GM standard.
I don't have test equipment here, but over the holiday I'll test the older speakers and let you know what I find. My $$$ is on the connector. There's a pea in the back of my brain that says a little di-electric grease in the connectors may have solved it all.
I'll keep you posted if anything pops up or changes. Thanks for all of your help.
AnswerHi John,
Thanks for the follow up. I hope your problem ends up being solved, one way or another.
Hopefully one day I'll be able to do some testing on a vehicle with this peculiar problem, and then I might be more helpful with questions like these.
Thanks
Brian
