Stereo sound dropping out
01-31-2022, 06:02 PM
#1
Stereo sound dropping out
Hi,
Long time reader but new poster. I have a 997.1 with Bose and aftermarket stereo. Usually, the stereo drops out to the point where it’s not usable, with furious relay clicking happening behind the back seats. At no point is the head unit restarting and it happens at any RPM if the car. It can sometimes intermittently work fine for a while.
The papers say the previous owner had a problem with, I think it was the cd changer, and instead of replacing opted to do an aftermarket conversion with some sort of expensive module, so the multi function steering wheel buttons still work.
From what I gather, this might be a problem with the fiber optical MOST system in the car, but I’m not so knowledgeable about it and how to fix.
I read that if any components or connections err defective it could cause this problem. Things like cd changer, navigation boxes and what not are not in use and could be removed, but is it a ring network that needs to be terminated in that case?
Whats a good way of trying to diagnose this error? I was thinking to cut the power to the head unit and see if the clicking still continued.
Long time reader but new poster. I have a 997.1 with Bose and aftermarket stereo. Usually, the stereo drops out to the point where it’s not usable, with furious relay clicking happening behind the back seats. At no point is the head unit restarting and it happens at any RPM if the car. It can sometimes intermittently work fine for a while.
The papers say the previous owner had a problem with, I think it was the cd changer, and instead of replacing opted to do an aftermarket conversion with some sort of expensive module, so the multi function steering wheel buttons still work.
From what I gather, this might be a problem with the fiber optical MOST system in the car, but I’m not so knowledgeable about it and how to fix.
I read that if any components or connections err defective it could cause this problem. Things like cd changer, navigation boxes and what not are not in use and could be removed, but is it a ring network that needs to be terminated in that case?
Whats a good way of trying to diagnose this error? I was thinking to cut the power to the head unit and see if the clicking still continued.
02-01-2022, 08:10 AM
#2
Rennlist Member
Not sure if it helps. I removed the dvd/Nav unit in the frunk thinking I didn't need it with my aftermarket head unit. When I did, I got zero sound, and clicking behind the rear seats constantly. Could be worth removing and reinstalling the dvd/Nav unit if it's still there. Check the connections from behind. It's a bit of a pain but doable.
02-01-2022, 08:38 AM
#3
That’s useful because then it adds to the theory that the clicking is caused by a MOST failure, either a device or a cable.
Probably it’s a connection that someone had already tampered with, so the adapter coming from the head unit should probably be checked. Do you have any idea what kind of relay would cause the clicking?
Probably it’s a connection that someone had already tampered with, so the adapter coming from the head unit should probably be checked. Do you have any idea what kind of relay would cause the clicking?
02-01-2022, 09:42 AM
#4
Rennlist Member
I am just guessing but something behind the rear seats but inside the car associated with the Bose system was clicking. Check the fiber optic cables in the frunk, behind the head unit, then behind the back seats.
02-10-2022, 02:51 PM
#5
Right so I solves this.
There isn’t any optical connection behind seats, it’s an analog signal coming from the Bose amp.
the circuit goes like this
head unit -> amp > cd changer > Navi > telephone > head unit
I slid off the cd changer cover, took off the trunk liner, exposed the last nuts of the cd changer and removed it. FO link comes out easy, but has to yank the power out with pliers after playing nice with it for 5 minutes.
removed the bracket for Navi and amp, went in with a thin flat head screwdriver from above and pushed the locking slots in at the front. I then slid it forward and disconnected.
Disconnected FO link of amp.
Verified that one link had red light.
shone a flashlight through the FO link from the cd changer. Verify that light is visible on the other amp link in the FO connector.
Verified that the light in the other fiber exited through one of the Navi ones. The one that did not light up is the one going back into the car.
I then disassembled the FO connectors of Navi and amp, and pulled out the one verified going from amp to cd changer.
I then removed the one verified going from cabin to Navi (the one that did not have any light going through it when testing with flashlight. This one I inserted into the amp FO connector and re-connected to amp.
Voilà, uninterrupted music! Probably it was the Navi unit causing this.
Afterwards, I also removed the phone module under the passenger seat. This one I used a FO MOST loopback cable to bridge the circuit.
End result is three control units and brackets out of the car, and a roomier front trunk. Also the MOST loop now has less connections and is shorter, with only the head unit and amp connected.
There isn’t any optical connection behind seats, it’s an analog signal coming from the Bose amp.
the circuit goes like this
head unit -> amp > cd changer > Navi > telephone > head unit
I slid off the cd changer cover, took off the trunk liner, exposed the last nuts of the cd changer and removed it. FO link comes out easy, but has to yank the power out with pliers after playing nice with it for 5 minutes.
removed the bracket for Navi and amp, went in with a thin flat head screwdriver from above and pushed the locking slots in at the front. I then slid it forward and disconnected.
Disconnected FO link of amp.
Verified that one link had red light.
shone a flashlight through the FO link from the cd changer. Verify that light is visible on the other amp link in the FO connector.
Verified that the light in the other fiber exited through one of the Navi ones. The one that did not light up is the one going back into the car.
I then disassembled the FO connectors of Navi and amp, and pulled out the one verified going from amp to cd changer.
I then removed the one verified going from cabin to Navi (the one that did not have any light going through it when testing with flashlight. This one I inserted into the amp FO connector and re-connected to amp.
Voilà, uninterrupted music! Probably it was the Navi unit causing this.
Afterwards, I also removed the phone module under the passenger seat. This one I used a FO MOST loopback cable to bridge the circuit.
End result is three control units and brackets out of the car, and a roomier front trunk. Also the MOST loop now has less connections and is shorter, with only the head unit and amp connected.
Last edited by NoTurboRequired; 02-10-2022 at 02:53 PM.
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cjarrett (02-10-2022)
02-10-2022, 03:06 PM
#6
Rennlist Member
This is super helpful, I'd love to get rid of the phone unit, DVD nav, and CD changer. So you used just 1 MOST Loopback?
Do you have a link to the one you bought for this?
Do you have a link to the one you bought for this?
02-10-2022, 03:16 PM
#7
That’s great, it took forever to write on my phone.
Yes, I only used one, which I bought from a local car audio store. It’s a female connector, so I’d you search for MOST loopback connector you’ll find it easily online.
This kind of fiber optics uses a big plastic tube, not fiber glass strands like many seem to think. So they can withstand a lot of abuse and you don’t need to worry working on them.
Disassembling the FO connectors requires pushing out the blue middle pin and then using a very small screwdriver to undo the latching clip locking the fiber sleeve into the plug, preventing it from sliding out. If you’re clumsy, just order a Tyco MOST connnector housing online while you’re at it. They’re kind of single use.
Yes, I only used one, which I bought from a local car audio store. It’s a female connector, so I’d you search for MOST loopback connector you’ll find it easily online.
This kind of fiber optics uses a big plastic tube, not fiber glass strands like many seem to think. So they can withstand a lot of abuse and you don’t need to worry working on them.
Disassembling the FO connectors requires pushing out the blue middle pin and then using a very small screwdriver to undo the latching clip locking the fiber sleeve into the plug, preventing it from sliding out. If you’re clumsy, just order a Tyco MOST connnector housing online while you’re at it. They’re kind of single use.
The following users liked this post:
cjarrett (02-10-2022)
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02-13-2022, 11:51 AM
#9
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hi
I'm not sure if it will help. I thought I didn't need the dvd/nav unit in the trunk because I have an aftermarket head unit. When I did, I received no sound and continual clicking behind the back seats. If the dvd/Nav unit is still there, it could be worth removing and reinstalling. Examine the connectors from the back. It's a hassle, but it's achievable.
I'm not sure if it will help. I thought I didn't need the dvd/nav unit in the trunk because I have an aftermarket head unit. When I did, I received no sound and continual clicking behind the back seats. If the dvd/Nav unit is still there, it could be worth removing and reinstalling. Examine the connectors from the back. It's a hassle, but it's achievable.