Intermittent audio fault - Sometimes Power but no sound
Discussion
Hi
I have an infuriating audio problem with my 2000 Merc...
Occasionally (1 time in 7?) when I switch the unit on, there will be Power (display shows the radio station, CD etc) but no sound from the speakers.
The solution is to remove the head unit and disconnect the connector block for the speakers from the back of the stereo and re-connect it. As soon as the speakers block is reconnected, it works as it should.
There are 3 blocks that connect with the rear of the head unit (in addition to the aerial and CD fibre input);
One that is exclusively connected to the CD Autochanger in the boot
One that is exclusively for the speakers (ie +ve and -ve for each location)
One that provides Power/elec aerial etc - There is no wire to the audio mute connection for a phone etc
It is only when I disconnect and reconnect the speaker block that I get sound again.
The mode that the unit is in makes no difference - eg CD/Radio/Other, nor does it make any difference whether it is switched on when the ignition comes on/off, the "Mute" function on the head unit works correctly and is not showing as "Muted" when the fault occurs.
I have tried changing the head unit for another identical Audio 10 - same issue, no difference
I have tried wiring the speakers directly to the rear of the speaker block and unplugging them from the regular speaker connectors (ie bypassing the car wiring to the speakers)
I have tried changing the car battery, same issue, no difference.
I have tried disconnecting the CD player block, same issue, no difference.
I have replaced the speakers - same issue, no difference
I am *guessing* that my final option is to change the speaker block connector? Is it possible that the problem is a fault within the block? (I cant see anything wrong, but the link below suggests it could be a short on one of the speaker connections?
https://help.retromanufacturing.com/knowledge-base...
The Head Unit is a Becker/Alpine Audio 10 with CD controller (and 6 CD in the boot) - Original fitment.
There is *no* external amp - the rear of the head unit is wired directly to the speakers
Does anyone have any other suggestions please?
I'd convinced myself that there was a short in the speaker wires, but spent an afternoon removing trim to get to the speakers and bypassing them, only to get the same issue on replacement wires.
I have an infuriating audio problem with my 2000 Merc...
Occasionally (1 time in 7?) when I switch the unit on, there will be Power (display shows the radio station, CD etc) but no sound from the speakers.
The solution is to remove the head unit and disconnect the connector block for the speakers from the back of the stereo and re-connect it. As soon as the speakers block is reconnected, it works as it should.
There are 3 blocks that connect with the rear of the head unit (in addition to the aerial and CD fibre input);
One that is exclusively connected to the CD Autochanger in the boot
One that is exclusively for the speakers (ie +ve and -ve for each location)
One that provides Power/elec aerial etc - There is no wire to the audio mute connection for a phone etc
It is only when I disconnect and reconnect the speaker block that I get sound again.
The mode that the unit is in makes no difference - eg CD/Radio/Other, nor does it make any difference whether it is switched on when the ignition comes on/off, the "Mute" function on the head unit works correctly and is not showing as "Muted" when the fault occurs.
I have tried changing the head unit for another identical Audio 10 - same issue, no difference
I have tried wiring the speakers directly to the rear of the speaker block and unplugging them from the regular speaker connectors (ie bypassing the car wiring to the speakers)
I have tried changing the car battery, same issue, no difference.
I have tried disconnecting the CD player block, same issue, no difference.
I have replaced the speakers - same issue, no difference
I am *guessing* that my final option is to change the speaker block connector? Is it possible that the problem is a fault within the block? (I cant see anything wrong, but the link below suggests it could be a short on one of the speaker connections?
https://help.retromanufacturing.com/knowledge-base...
The Head Unit is a Becker/Alpine Audio 10 with CD controller (and 6 CD in the boot) - Original fitment.
There is *no* external amp - the rear of the head unit is wired directly to the speakers
Does anyone have any other suggestions please?
I'd convinced myself that there was a short in the speaker wires, but spent an afternoon removing trim to get to the speakers and bypassing them, only to get the same issue on replacement wires.
Edited by iDrive on Sunday 21st May 09:19
Well, it sounds like the speaker block is the only thing left to change!
Some stereos check that speakers are connected before allowing the amp to power up, as the amp could be damaged if not. So a poor connection somewhere in the block (within the radio itself is likely ruled out as you say you've swapped that) or between the block and the stereo could be the culprit.
You could, depending on the design of the block/connectors, use a very thin probe to release each connector from the block in turn (there's usually a small tab that sticks out of the metal connector and so stops it being simply pulled out of the block), and check that it's making firm contact with the wire crimped into it, and maybe just give the end that slides onto the radio a gentle tweek tighter to make sure there's good contact there. Finally, as you say you've re-wired onto this block, you've presumably got somewhere to check the continuity for the first few inches of the wires themselves from the connector block back to wherever you've tapped into them behind that.
Oh, and one more thought before finishing, sorry... on the same idea of checking the speakers are present and correct by the stereo before start-up, one (or more?) of your speakers may have some internal damage/problem and so not show the 4ohm expected when tested... occasionally. If testing/tweaking/changing the connector block doesn't work, consider swapping out speakers one at a time for known good.
Good luck, I hate intermittent faults!
Some stereos check that speakers are connected before allowing the amp to power up, as the amp could be damaged if not. So a poor connection somewhere in the block (within the radio itself is likely ruled out as you say you've swapped that) or between the block and the stereo could be the culprit.
You could, depending on the design of the block/connectors, use a very thin probe to release each connector from the block in turn (there's usually a small tab that sticks out of the metal connector and so stops it being simply pulled out of the block), and check that it's making firm contact with the wire crimped into it, and maybe just give the end that slides onto the radio a gentle tweek tighter to make sure there's good contact there. Finally, as you say you've re-wired onto this block, you've presumably got somewhere to check the continuity for the first few inches of the wires themselves from the connector block back to wherever you've tapped into them behind that.
Oh, and one more thought before finishing, sorry... on the same idea of checking the speakers are present and correct by the stereo before start-up, one (or more?) of your speakers may have some internal damage/problem and so not show the 4ohm expected when tested... occasionally. If testing/tweaking/changing the connector block doesn't work, consider swapping out speakers one at a time for known good.
Good luck, I hate intermittent faults!
I'm embarrassed and confused, but I have solved the issue (and can't work out why it was an issue...)
The car had a bluetooth device placed in a cigarette lighter - one that picks up the blue tooth signal and transmits it local so that the old-school stereo can play it.
The issue was that somehow the bluetooth transmitter was interfering with the old-school stereo - I have *no* idea how this could be so - There was no line-in interrupt and the headhunt should only play when tuned to the right channel.
Even when tuned to s different frequency it would still mute the CD/Radio.
Its bizarre.
On the plus side, I took the opportunity to replace two pairs of OEM speakers.
The car had a bluetooth device placed in a cigarette lighter - one that picks up the blue tooth signal and transmits it local so that the old-school stereo can play it.
The issue was that somehow the bluetooth transmitter was interfering with the old-school stereo - I have *no* idea how this could be so - There was no line-in interrupt and the headhunt should only play when tuned to the right channel.
Even when tuned to s different frequency it would still mute the CD/Radio.
Its bizarre.
On the plus side, I took the opportunity to replace two pairs of OEM speakers.
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