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High pitched whistle from under dash

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I have a high pitched whistle coming from under the dash. It is electrical as when you disconnect the battery it stops.
It seems to be coming from a control box directly in line with the centre console attached to the bulkhead. I did undo the multiplug to this and it did not stop however so this could be a red herring.
It is driving me crazy not to mention it could be the start of something bad so any help would be appreciated.
 
There is a cooling fan in the air con control unit that can sometimes get clogged. The unit comes out much like a stereo unit. There are four holes that you insert a special tool or something you can make up and the unit will slide out. You should be able to see the fan easily and be able to clean any debris out.
This fan continues for some time after the ignition is turned off (about 15 minutes I think) which is why it stops if the battery is removed. Try going back to the car after 15 minutes or so after you next come back from a drive and see if the noise has stopped, then you'll know it is this for sure.
 
Agreed, it's quite likely to be the temperature sensor fan in the heater control unit. If that idea does not check out try removing fuses one at a time from the fuse box at back left of under bonnet area (as you look at it) until you find the fuse that stops it.
 
Thanks for the replies guys.

The only issue with the solution here is that the whistle is there all the time. I had not used the car for three weeks and it was whistling at me when I got in.

An electronics friend of mine has suggested that components in a power supply can make this noise and asked me if it varies when I turn other stuff on and it does.

He suggested the resonance at a certain frequency can produce such a whistle. With this in mind I have to find a power supply that is constantly powered. Could this be the alarm for instance or a control unit?

Many thanks
 
Chris,
I think remove fuses one at a time until it stops - that should at least tell you what it is.

Approx what size is it? When you say "attached to bulk head" - which side (bonnet or inside car?)
 
Hi Chris

Just a suggestion but try disconnecting the Stereo as that is powered at all time to keep the memory. It has two feeds. Permanent from the battery & Switch supply from the ignition

Good luck

Graham
 
ORIGINAL: sidned

There is a cooling fan in the air con control unit that can sometimes get clogged. The unit comes out much like a stereo unit. There are four holes that you insert a special tool or something you can make up and the unit will slide out. You should be able to see the fan easily and be able to clean any debris out.
This fan continues for some time after the ignition is turned off (about 15 minutes I think) which is why it stops if the battery is removed. Try going back to the car after 15 minutes or so after you next come back from a drive and see if the noise has stopped, then you'll know it is this for sure.
Click to expand...
Am I right to assume this is the unit to the right of the stereo? My aircon stopped functioning right after I installed my new stereo. Suggestions were that I had inadvertently disconnected a pipe from the rear of the aircon unit as I pushed the stereo into place. Would this make sense?

Thanks, David.
 
ORIGINAL: MrHappy

Am I right to assume this is the unit to the right of the stereo? My aircon stopped functioning right after I installed my new stereo. Suggestions were that I had inadvertently disconnected a pipe from the rear of the aircon unit as I pushed the stereo into place. Would this make sense?

Thanks, David.
Click to expand...

Yes, very easy to do (except not a pipe, all electrics back there, but easy to foul one of them) - or indeed numerous other electrics. My speedo and fog lights both stopped working when I had my new audio system fitted.
 
Found the whistle

After removing 41 fuses and all the relays (one at a time of course). This did not stop the noise.

Found three fuses under the dash and the first one stopped the noise. Worked out that these were for the PA1000 alarm.

I moved the seats as far back as I could and managed to get closer to the noise. I removed a small access panel in the drivers footwell on the side of the gearbox tunnel and there was a small siren (black and red wire to it) loose about the size of a 10p piece whistling at me.

I checked the PA1000 manual and thought hey this must be the valet mode but unfortunately it isn't.

So I still have a problem but I now know it is the alarm which is clearly going to drain the battery in double quick time.

Does anyone know if the PA1000 has it's own alarm for low current etc..

Many thanks
 
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