Since I bought the car over 4 years ago, i’ve always been plagued by constant alternator whine through the driver side speaker and tweeter. None on the passenger side. Today I had an exploratory look under the dash to try to find if there is anything obvious that may be causing it. However, i quickly realised that I don’t know how to perform any sort of electrical check that would help identify a problem.
So far I have been round as many earth points as I can:
Under each headlight
Near exhaust manifold
Under wiper motor
Either end of the dash, inside the door
Power Plant Frame
Boot near the battery
While I have cleaned and reseated those - no sign of rust at any - there has been no change.
So the things i’m thinking are:
Is there a reason why whine would impact one side and not the other?
The car when new would have had a Bose sound system. This has been removed and I have tried two different head units and two different speakers with no change. So it must be a wiring issue surely?
As an import, it's also had an odometer conversion. Occasionally the needle on the speedo goes crazy. Could this be related in any way?
Have I missed any other earths?
There is a TOAD immobiliser. I've heard they can cause problems. Is there anyway to isolate this to see if it has any effect?
There are a couple of loose wires i've found. One is a short piece of earth wire from the radio harness that just ends with bear wire. I've wrapped this with tape. The other is the same as the wire going to an flashing LED which I think is related to the immobiliser. That's at least tied off and wrapped with tape.
Any advice on how to troubleshoot this or where to look would be really helpful.
Never seen a toad immobiliser cause radio interference.Firstly ,make sure there is a good ground bond between the radio and body/chassis frame.If the whine is only coming out of the left front speaker,then it is likely to be induced through the wiring harness.I would run new speaker cables away from the main harness and into the door.Disconnect existing wiring to this door.
The speaker wires should only go back to the speaker terminals on the amplifier, and not be grounded anywhere else. The same goes for any external signals that might be fed into the amp.
The noise on one side only can be because of a few possible reasons:
a power ground from the amp is being shared by the return from that speaker; any ripple and noise on that share ground will appear as a signal fed through the speaker and back into the amplifier output.
an external input (CD player in boot perhaps?) is using the power ground as the earth return for that channel.
something similar
The wires might actually be connected correctly, but there could be a short between the speaker return and the power ground.
Unplug the connector from the amp and check if there are any shorts between the wires going to it, specifically the power grounds and speaker returns. Beware of the +12V wires on different fuses.
In the spirit of missfire’s advice I connected a spare speaker to the rear outputs of the head unit to check to see if there is any noise and there was none. I will try it with the front cables in question, but i imagine the fact that two head units have not cured the problem, it would be reasonably safe to say it’s going to be some interference along the main harness which twists and turns around a few other harness runs. Just looking at the harnesses they are all really well wrapped in electrical tape so it’s impossible to see anything without pulling it all out which I want to avoid.
RichardFX, thanks for the suggestions. I am an electrical novice, so I’m not sure i quite follow the the first point. Are you saying that the main ground for the head unit to chassis could also have the speaker cable spliced/connected to it at some point rather than it simply returning to the head unit? Then any interference on the main power ground is going to pass into the speaker cable, go through the amp, and back into the speaker? I suppose re-running a new cable to the door speakers may solve this?
Does it make any difference that the door tweeter tends to be worse than the main speaker?
Wrt to the immobiliser, I read an guide to installation of a similar unit to mine which states fundamentally not to share a ground with the immobiliser. That’s why I was trying to look for where the ground from the immob was heading. It goes and gets lost in the mass of electrical tape harness so it will be a job tracing that.
I know that the immobiliser was fitted when after the car was imported to the UK which is when I assume they removed the Bose system. So my suspicions are that the miswiring occurred at that point.
For completion, there is no boot CD changer, although there is a curious switch that has been installed which turns on the ‘high’ level tail light - perhaps as the rear fog light…
So it’s far from a factory harness loom.
I guess if running new cable works (perhaps under the carpet) then my next question will be how best to run the cable into the door? There’s the rubber conduit running from chassis to edge of door - is it a door off job or is there a special method?
Just by way of an update and the fact that things are getting a little weird.
The harness from the head unit has:
Front Left speaker cables white +ve and white/black -ve.
Front Right speaker [whining speaker] cables grey +ve and grey/black -ve
From HU harness, the wiring colours change before changing again in the door. I haven’t made a note of the all the changes in wiring colour. I’ll do that when it’s light out.
I’ve tabulated the combinations I’ve tried to attempt to communicate more clearly:
Key:
Yes = cables connected through the existing wiring [HU harness into harness adaptor into car harness] or working as before.
No = Cable disconnected or no sound from speaker.
New = New cable connected - run to right hand speaker
White White/Black Grey Grey/Black Left Speaker Right Speaker
Yes Yes Yes Yes Yes Yes with whine and lower volume (standard and what i’m trying to fix)
Yes Yes NO NO NO NO
Yes Yes New New NO* Yes quieter than normal left speaker
Yes Yes NO Yes Yes** NO
Yes NO NO Yes Yes*** NO
Yes New New Yes Yes Yes much quieter than LH and HU flashed with a miswiring failure. Switched the polarity on the RHSpeaker and worked but quiet.
*Very odd, I would have thought the left speaker would work with white + white/black cables connected. Suspect a miswiring.
**So perhaps the grey/black is actually +ve or -ve for the left speaker rather than the right
***Does this confirm that the car’s harness is miswired?
So… a couple of things:
It appears there is a miswiring. I should try only grey and white/black to see if the right speaker works.
The fact the right speaker is always quieter than the left hand speaker (normal operation I have a +4 bias to the RH speaker on balance). What does this mean? I have attached a different speaker to this side and it has demonstrated the whining and quietness of the other one. Could there still be an amp inline somewhere? Doesn't the Bose system normally have 2 amps - one left, one right? Could it be that the bose amps weren't removed and one is knackered? My question then would be where are the amps? I've never seen an image or diagram of where they are supposed to be.
You might need to consider starting from scratch if you cannot trace each wire from start to finish, checking for continuity and shorts with a test meter and maybe another pair of hands and eyes.
It appears someone has already ripped out the original wiring which should have been something like this below, assuming you have a non-Bose Mk2. (Bose speaker wiring has similar colours, but then it is all different with the complication of the extra Amplifier which is powered via a relay switched by the head unit.)
Just follow the line across the page from radio connector through the wire colours to the item it is connected to. If you have tweeters they should be just in parallel with the main speaker in the door, each tweeter should have a cross-over capacitor to protect it from the bass.
Audio Unit wires mid colour final colour Item/Function
1A Blu/Blk +12V from Radio Fuse
1C Blu/Red +12V from Room Fuse
1D Gry/Blk control to Power Antenna
1E Red/Blk from Interior Lights
1F Gry/Red from Interior Lights
1K Yel/Red Yel/Red Yel/Red (or Yel/Grn) to Left Speaker(s) +ve
1L Yel/Blk Yel/Blk Grn (or Yel/Blk) to Left Speaker(s) –ve
1M Yel/Grn Yel/Grn Yel/Red (or Yel/Grn) to Right Speaker(s) +ve
1N Grn Grn Grn (or Yel/Blk) to Right Speaker(s) –ve
Unfortunately, the car did once have a Bose system which it could be even more of a pain.
I tried checking for continuity between the connector at the HU and speaker end for the RH speaker but didn’t get anything but the speaker works. Left and right channels work correctly so does that mean i’m either not checking it properly or would it suggest some kind of a relay switch as you mention?
I will have to have another look at some point.
Driving home this evening with the setup where the speakers are balanced, the whine from the RH was quite strong and when i plugged in a usb cigarette lighter adaptor to charge my phone there was a significant increase.
You mention there’s a ground in the centre of the dash. Is that readily accessible with just the HU out or is it buried and a dash out job?