GTE Electrical Whine

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tyang
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Re: GTE Electrical Whine

Post by tyang »

Hi Graham,

Do you have a voltmeter? Even if your car is starting and running, make sure the alternator is charging. Put a voltmeter at the battery while the car is running and see if you're getting anything more than 13 volts at the battery, especially when you rev the engine a little bit. If it's your voltage regulator is making noise, it could be the supply wire to the VR that you're disconnecting which is not good!

Tom
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chris
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Re: GTE Electrical Whine

Post by chris »

Graham, have you found the culprit?
2837GT
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Re: GTE Electrical Whine

Post by 2837GT »

Hi Tom,
I bought a stethoscope by recommendation and have made progress with the location if not the cause of the electrical noise.
The whine is loudest in two places, behind the metal box structure screwed onto the bulkhead (Which has the hood latch mounted on it, and when I place the stethoscope on the dash behind it.
Is this where the VR lives?
The car is due to go over to Terry Hoyle soon (For other work) who has a good classic car electrician but I would to understand the issue and point them in the right direction.
My voltmeter is at my London home and I am in Devon so I have ordered another one and will test the voltage as you suggest.
Best
Graham
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tyang
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Re: GTE Electrical Whine

Post by tyang »

Hi Graham,

The coils are mounted to that bracket, and the heater fan is directly below that area behind the dash. I still don't think the coils would make that noise, but there's not much back there! The VR is either behind the fuse panel or behind the glove box door inside the car. Look under the passenger side footwell and look for a plastic red box 3x4 inches square. If it's behind the fuse panel, take the aluminum cover off of the fuse panel and look for a steel covered box in the same dimensions.

Is it a regular stethoscope like at the doctor's office? Sometimes those are too sensitive and hear everything. If it has a probe like a mechanic's stethoscope, you may be able to pinpoint more accurately. If you're using a medical stethoscope, try using a screwdriver to touch certain areas and place the stethoscope end on the handle of the screw driver. If you look down past the two distributors, you will see a round sheet metal box with two hoses coming off it. That is the heater motor assembly mounted on the firewall. Inside it is the heater motor. Have a listen there to try to eliminate the motor from making the noise. The wire for the heater motor pops out the bottom of the heater box under the dash, but is obscured by the center console.

Tom
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2837GT
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Re: GTE Electrical Whine

Post by 2837GT »

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2837GT
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Re: GTE Electrical Whine

Post by 2837GT »

Hi All,
Voltmeter across the battery suggests nothing wrong with the VR.
All other electrical components tested and functioning normally.
Despite the mystery wire being plugged into the top left fuse, I now believe the problem lies with the blower motor and not the ignition system, so the next step will be its removal.
2837GT
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Re: GTE Electrical Whine

Post by 2837GT »

Here is an update on the slightly boring (multi platform) story of an annoying noise seemingly emanating from behind the box section on bulkhead to which the bonnet catch is attached.

Some of you may recall that the noise stops with the removal of a black wire running to the top LH fuse.
That wire looks 'non original' being too new, too thick looking.
This wire disappears behind said box section, but I have now found that it emerges from the other side, runs along the bulkhead, dives into the car on the LHD driver side and connects to the ignition switch.

Interesting facts are:

The car starts with this wire disconnected.
The VR functions with this wire disconnected.
All the cars electrical functions, lights, blowers, fans etc function with the wire disconnected.
The noise is not coming from the coils, distributors, VR, or anything obviously useful to the operation of the car.

So the temptation is to unplug and tape off the wire, never hear the still unexplained noise again, and move onto more interesting subjects.

Yet, there is one not of caution. When I last started the car with the wire in place, I removed the wire while the engine was running (but still basically cold). The revs dropped instantly and the engine stalled. Whilst I was then able to re-start the car and nurse the engine up to temperature, it bothers me that the removal of the wire had a noticeable effect.

Or was it a coincidence?
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2837GT
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Re: GTE Electrical Whine

Post by 2837GT »

On the pictures above the wire is seen disconnected from the fuse box.
It runs seemingly un-broken from there, behind the box section pictured, and to the ignition.
The noise measured by Db meter and stethoscope seems to come from behind that box.
The wire when jiggled at the fusebox end moves at the drivers end before it disappears behind the water bottle on its way to the ignition. Therefore it doesn't run from the fuse, to some hidden device behind the box and thence the ignition. It is a single wire from ignition to fuse.
2837GT
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Re: GTE Electrical Whine

Post by 2837GT »

Exciting news !
I have discovered an after market toggle switch cleverly hidden well away beneath the dash. When you switch it from its current position the annoying noise stops. The car still starts and runs. All that happens is that the noise stops, exactly as if I had unplugged the black wire.
I think then that those of you who deduced that the issue could be related to an aftermarket anti theft device may well be right.
I am treating the case as “closed”.
Thank you all !
Hopefully I will buy everybody a beer at Pebble Beach....
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tyang
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Re: GTE Electrical Whine

Post by tyang »

Wow! What an ordeal. I'm glad you found it. Good on you!

Tom
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John Vardanian
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Re: GTE Electrical Whine

Post by John Vardanian »

So, what was the source of the noise?
PF Coupe
2837GT
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Re: GTE Electrical Whine

Post by 2837GT »

I still don’t know the answer to that question, just how to stop it.
I am more relaxed about it now, having eliminated all the major electrical components. That said, I will find out and report.

My new priority will be chasing an electrical fault that causes the overdrive fuse to (often but not always) blow when the system is engaged.
Previously the Steering column switch was rebuilt, the inhibitor switch on the gearbox replaced, the fuse box cleaned and a broken wire on the relay repaired. Yet still the fuse has a propensity to blow.
Anyway, that is another story and perhaps another thread.
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