Alternator whine & Speedo issues?

[I Like Waffle]

I get a really bad whiney noise from my alt under the hood when a loud bass note plays, however my speakers and subs sound good with no interference. At full tilt my voltage never drops below 13.5 at the HU or at the amp. Only problem is i can hear the whine under the hood from outside the car even with the hood closed. Anything i can do about this or is it just from current draw?

Also another thing which might or might not be a sign of a problem - my speedo jumps around like crazy on certain songs- varying from 5-10 mph jumps, and i cant figure out why //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif Figured it might have something to do with my power wire running past my cars main computer, maybe causing electronic interference or something? But i thought the speedo was mechanical with a cable that spins the dial since i have an old car?

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[tuomas 10+ year member]

Maybe its the speedo... have you tried board shorts?

 

[kentb 10+ year member]

has someone messed with your wiring lately?

i had a problem before, whenever bump and turn the lights on my gauges goes crazy.

it ended up being the ground point on the kick panel.

somehow it got messed up before

 

[I Like Waffle]

Ive messed with my wiring //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif Electrical wise ive removed the cat, smog pump, ac pump, ac condenser, ac idle kickup motor, and replaced all the engine ground/batt wires. I dont know if its EMR from my power wires going past the cars computer which is in the passenger kick panel in the front in older GMs. Or maybe its just vibrations? I have one of those "bouncy" speedo needles which doesnt accel smoothly, but rather bounces from 10-35-55 when i get on it hard for example. Only happens with high bass notes too i noticed

 

[Mike465 10+ year member]

It may be your alt belt has lossend up and is slipping.

 

[93dakota 10+ year member]

It may be your alt belt has lossend up and is slipping.

I agree i would say that the noise is your belt slippin on you alt, are you running a stock alt? also the spedo problem could be voltage. in my truck if i have any fast change in voltage my tach drops 1000rpm or so because it is electronically controlled. if that is the problem it is not worth worrying about.

 

[350Rocket 10+ year member]

That speedo is mechanical cable driven, nothing related to the electrical.

 

[rc10mike 10+ year member]

That speedo is mechanical cable driven, nothing related to the electrical.

Are they still like that on ALL cars?

 

[edzy 10+ year member]

get a new speedo cable. Pretty easy to install. That one is probly just worn out. You could disconnect it at the dash and try pouring some oil down it, and see if that helps. As far as alt goes.. ... So try the oil or new cable.

 

[350Rocket 10+ year member]

^^No, but all of that type of car are. Every one of my cars (1980's GM's) have noisy speedo cables in the cold. I would do as Edzy suggested.

 

[scoob8000 10+ year member]

I would hazard to guess on an 81' your speedo is mechanical. Coasting down the road turn the ignition off (not enough to lock up the wheel). Does the speedo still work? If so it's mechanical and has nothing to do with the electrical system.

Is the underhood whine always there? You could try taking the belt off the alternator and start the engine and see if it's gone..

 

[I Like Waffle]

i dont think its the belt slipping because the alt belt is tight as shit. I cant tell right now anyhow as i have no dbz due to burned up amp. Waiting for it to get back from the manufacturer. From what i can tell its just the strain on the alt from the amp. Not anything actually slipping. I have stock alt with 2 batts and >1200wrms so it might be struggling idk. No clue what the prob is with speedo. Doesnt bother me i just thought it was weird. Did i mention earlier that one of my power wires is like 3 inches away from my ECM thing? Thought that might have something to do with it from electromagnetic interference and all that bs but wasnt sure. Im gonna move it before the next install though.

 

[Louisiana_CRX 5,000+ posts]

Ive messed with my wiring //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif Electrical wise ive removed the cat, smog pump, ac pump, ac condenser, ac idle kickup motor, and replaced all the engine ground/batt wires. I dont know if its EMR from my power wires going past the cars computer which is in the passenger kick panel in the front in older GMs. Or maybe its just vibrations? I have one of those "bouncy" speedo needles which doesnt accel smoothly, but rather bounces from 10-35-55 when i get on it hard for example. Only happens with high bass notes too i noticed

there was a cat in your car //content.invisioncic.com/y282845/emoticons/confused.gif.e820e0216602db4765798ac39d28caa9.gif

 

[I Like Waffle]

catalytic converter? Did your rice not have one? //content.invisioncic.com/y282845/emoticons/tongue.gif.6130eb82179565f6db8d26d6001dcd24.gif