Constant electrical interference noise - especially with heated seats

[shad0wca7]

I was driving normally and this electrical whining sound over the speakers developed - very loudly. The following day it then seemed to resolve by itself.

Now two weeks later it’s happening again. It occurs when the engine is off (tried to record the sound in the video initially though it’s quite quiet) but is much louder when the engine is on.

It’s even louder when the heated seats are switched on. To me it sounds like a ground loop or grounding issue caused by a weak solder somewhere - finding out where is going to be a challenge however.

Has anybody encountered this already? I’d much prefer it to be an easy module fix…!

Video with sound here:

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[Unas2k5]

Sounds like a fan or something that’s spinning? Have you tried to pop the hood and listen from that end ?

 

[luca1290]

To me it sounds definitely like a grounding issue, you can hear it cycle from what I think is the duty cycle of the heating element of the seats, or some tension converter component in the module.
Or a bad module.

What I'll try to do is first try and disconnect a module at a time and keep it disconnected until the sound stops.
Then reconnect all the other modules and hope you find just one bad module.
Usually modules will share the same grounding point so my guess is if you disconnect enough modules at some time it will stop.

You definitely need the Workshop Service Manual and an electrical tester to see the procedure for ground testing. Usually you can test them on predefined spots to find the bad one by measuring the resistance between the ground of a module and a point on the chassis.

Keep a diagnostic tool at hand because the car will really be upset for this treatment and throw a lot of error codes.
If you have Forscan you can hook a very stable charger and check the voltage reported by every module. Usually bad grounds tend to have modules report lower and/or unstable tension, especially if loaded (heat the seats, turn on the radio, hit the defroster...)

 

[shad0wca7]

To me it sounds definitely like a grounding issue, you can hear it cycle from what I think is the duty cycle of the heating element of the seats, or some tension converter component in the module.
Or a bad module.

What I'll try to do is first try and disconnect a module at a time and keep it disconnected until the sound stops.
Then reconnect all the other modules and hope you find just one bad module.
Usually modules will share the same grounding point so my guess is if you disconnect enough modules at some time it will stop.

You definitely need the Workshop Service Manual and an electrical tester to see the procedure for ground testing. Usually you can test them on predefined spots to find the bad one by measuring the resistance between the ground of a module and a point on the chassis.

Keep a diagnostic tool at hand because the car will really be upset for this treatment and throw a lot of error codes.
If you have Forscan you can hook a very stable charger and check the voltage reported by every module. Usually bad grounds tend to have modules report lower and/or unstable tension, especially if loaded (heat the seats, turn on the radio, hit the defroster...)

This is great advice thank you. I’m going to pick up a diagnostic tool and set aside some time for this.

 

[luca1290]

This is great advice thank you. I’m going to pick up a diagnostic tool and set aside some time for this.

If I may suggest, instead of going for some generic code reader, invest in a good interface and Forscan for Windows. The cost of the license and the interface is equal to the generic code reader but you can do so many things more...
You'll find the recommended interfaces for Forscan on their site.

 

[shad0wca7]

If I may suggest, instead of going for some generic code reader, invest in a good interface and Forscan for Windows. The cost of the license and the interface is equal to the generic code reader but you can do so many things more...
You'll find the recommended interfaces for Forscan on their site.

I’ll go that route - not worth skimping on dodgy equipment for this and being extra frustrated.

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