Alarm sound

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Night_train01

Member
Joined
Dec 27, 2015
My car is in storage for the winter, I recently have a high pitch sound when I turn the key to the ignition position. I have not been able to pinpoint where the sound is coming from though. It sounds like an alarm of some sort. I am hoping it is caused by a low battery and not something more serious. Anyone else have experience with this? I have not tried to start the car to see if the irritating high pitch goes away.
 
I do get the usual chime when the doors are open and the key is in the ignition, this high pitch is separate from those chimes. I have put my battery on charge to see if the noise goes away with a full charge.
 
I forgot to mention that I have removed the coolant temp warning sensor, this is the one that controls the warning light on the dash.....but I don't think GM had any type of sound that went with the light to let you know the engine is overheating
 
If it's a steady sound very high pitched, and not wailing or and up/down sound, then try sticking your ear close to the alternator and see if it's coming from there.
 
I put a battery tender on it yesterday before I left for work and when I turned the key last night the noise was gone
 
Night_train01 said:
My car is in storage for the winter, I recently have a high pitch sound when I turn the key to the ignition position. I have not been able to pinpoint where the sound is coming from though. It sounds like an alarm of some sort. I am hoping it is caused by a low battery and not something more serious. Anyone else have experience with this? I have not tried to start the car to see if the irritating high pitch goes away.
Click to expand...

The original owner may have installed a Casper's Audible Knock Detector. This small alarm type device is usually installed behind/under the dash somewhere where you can't see it. It goes off if it sees knock timing retard, letting you know to lift of the throttle when it happens.

Why would it be going off now? Who knows? It does this in my car for all types of weird reasons. Sometimes when my battery is low from sitting and sometimes just when I start the car and sometimes it doesn't stop and I have to shut the engine and restart for it to go away. I often experience this just as you have.

Many times I have thought to remove it. But this unusual behavior clears up when voltage is correct or after the car is restarted. Then it behaves as normal. But still, I no longer have any use for it. As my set-up can't effectively make use of it due to the noises it naturally makes as a performance built engine. Besides, I have verified and am absolutely certain it isn't knocking under these conditions.

I pretty sure you have one and just don't know it?
 
Last edited:
NY, that just might be the answer. When I recently installed a alky system I noticed a white plastic box behind the glove box.....it definitely isn't stock looking, it has a small circuit board inside of it, that could be a irritating sound I was hearing.
 
Night_train01 said:
NY, that just might be the answer. When I recently installed a alky system I noticed a white plastic box behind the glove box.....it definitely isn't stock looking, it has a small circuit board inside of it, that could be a irritating sound I was hearing.
Click to expand...
Nope, I don't think that's the one. Go to Casper's website and take a look. It's black with a square base and a round top.
 
I did take a look at the Caspers site, it doesn't look like the plastic box I see on my car, however I am going to explore a little and see what else I can find hidden behind the dash. Thanks for you help....
 
I think it's the audible caspers knock alert. I have it on my GN and have the same issues with it making noise after I start the car sometimes I have to turn the car off and restart it to get it to stop. Most of the time it works properly but it scared the shit out of me when I first started the car after installing a built bottom end and thought it was hearing knock I couldn't. The second time I started the car it turned off after a few seconds. It has a red, yellow and black wire going to it if I remember correctly. HTH
 
NY Twin Turbo said:
Never heard of this before but it sounds like it can't be good! (I'm thinking about the possible need for a fire extinguisher!) How does the alternator make noise?
Click to expand...

The voltage regulator is a bang-bang controller. It oscillates to control the output voltage of the alternator.

RemoveBeforeFlight
 
Some alky. system controllers use a PWM output which can be an audible high frequency when ON.

Pinpoint the source if you can that's the best way to find it.
 
Since you didn't try and start it, and didn't put a votmeter on the batter, or look at BAT on the scanmaster.....


.....was the dome light full brightness when you opened the door? Did the batter charger throw a spark when you hooked up the last clip?
 
The dome lights were on, I have been working on the interior for a couple hours and my guess is the battery was low.
 
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