midnightfirews6

iTrader: (1)

My car has been doing this since I can remember; it buzzes at idle and low RPM's and sometimes the choke light comes on. The volts gauge stays pegged at 14 when I'm cruising and dips a little at stops, nothing major, and the car has been doing the buzzing thing for several years and over 20,000 miles so if it were the alternator I'd think it would be dead by now. The battery is a crapster Rural King one and it's old but it still holds charge. I tested it yesterday and it had a little over 12V and a few more CCA than it was rated. I checked the C/K fuse, it's not blown. The car has 92,000 miles and runs great, the buzzing is just irritating. I've read the threads that said to check the fuses and the alternator but like I said above they seem fine. Any ideas on what else to check?

NINÅ

midnightfirews6

iTrader: (1)

Oh sorry I should've been more clear, it's definitely a warning buzzer. I just don't know what's causing it.

TreeFiddy

Do the choke light and buzz happen at the same time, or are they independent? Pull the warning buzzer out of the 'convenience centre' under the dash, see if that stops the noise.

Apeiron

Replace the choke heater fuse.

rusty vango

this was a common thing with these back when they were new ,i have the factory fix info somewhere here,as soon as i find it, ill post it, meanwhile ,good luck

NorwoodGMPlant

My 84 Trans Am is doing the same thing. My car is mostly a show car and is rarely driven (52,000) original miles. The car has recently sat in my garage since about October of last year. It never made the buzzing/chose light noise until I recently changed the battery and got it started again. (My other battery had a dead cell and needed to be replaced). Can anyone guide me on what part would need to be replaced, is it easy to fix, and where to get the part?


Thanks,
Michael

sofakingdom

iTrader: (1)

It's probably the diode trio. Inside the alt. Not hard at all to change out, not too $$$.

OTOH, if the alt is old, ... might as well just replace it.

NorwoodGMPlant

Thanks, I've seen where some people said it was the choke heater fuse (which I would assume would be an easy fix as well?) My problem is the car is all stock and original, except for tires and battery and I'm trying to keep everything with the original parts do you thing the alternator is going bad? I am trying to avoid changing out the original unless I'm forced to.

sofakingdom

iTrader: (1)

Alternators don't last forever. Bearings wear out for example.

Not sure what difference it would make whether the alt is "The Original One" as opposed to an identical one that's been rebuilt... they're kind of all the same.

It's possible to rebuild an alt yourself if you know what you're doing and have the right tools. Hardest part is getting the shaft out of the front bearing without destroying the retainer. Not impossible, but not easy either, usually, especially not the first time. You can then replace the front bearing (the back one in that model of alt hardly ever goes bad), any internal electronic parts such as the diode trio that have failed, put in new brushes, and it'll be almost as good as new again.

NorwoodGMPlant

Will there be a marking on the Alternator to let me know if its the original factory one or how could I tell if it's been replaced before? Also, the buzzing noise doesn't start until it gets to a smooth idol, other than that it never does it until it reaches that point. Car starts fine and everything else works fine, thats why I'm confused about the alternator needing to be replaced. Thanks for all the information!

sofakingdom

iTrader: (1)

Needs a diode trio.

The alt is 3-phase. The diode trio is a half-wave rectifier on each phase. Each phase produces a pulse for 1/3 of a revolution of the alt. When one diode goes out, only 2 of the 3 phases still work; so for each revolution of the alt it puts out pulse... pulse... nothing... pulse... pulse... nothing... The light comes on during the nothing interval. If that lasts long enough (i.e. if the alt is turning slow enough) the ckt that lights it has time enough to respond and turn it on for that brief interval, then turns it out the next time it gets a pulse. That's why it only lights at idle, and doesn't really come on full brightness.

The choke relay buzzes at the same time, since it's also driven by the diode trio.

Needs a diode trio.

By the time you finish dinking around with that inside an alt that's ... how? ... old, you will have spent about 3 - 4 times the time it would have taken to just change out the alt. Plus, as these things always seem to work, you'll fix the diode trio, and next week, some other part of it will fail, and you'll have to buy another one anyway. Might as well just do it and get it over with.

I know of no "marking" that means it's the original factory one. My guess would be, on a 84 car, it's probably on its 4th alt or thereabouts by now; meaning, the odds of it being the one the car first came with, are somewhere between zero and none. Not that it particularly matters; "rebuilt" ones are identical in every way externally to the original, and as far as I'm aware the car couldn't care less what alt is on it as long as it works. ("works" as in, full time, not just 2/3 of the time)

NorwoodGMPlant

Thanks! I am going to go ahead and replace it. I appreciate all of your help!