Alternator whine

[petriach]

Comes in both over my radio's speaker(especially at idle when squelched and volume turned up,K0BG's site has an example),and I can hear it from the alternator itself(high pitched whining). You don't hear it in transmitted audio,or in my car's stereo.

The sound will change depending on RPMs and electrical load,whine gets louder from the alternator itself as more of a load is placed on it. I think it's the rectifier/diodes going bad.


Alternator is not that old,only a few months,I got it from O'Reilly's to replace the OEM one in my car that's output stud got messed up. The part # is 01-3681
2nd one from them,the first one actually shrieked and only gave 12.3V maximum,so I took it out,hooked a charger to the battery,and went and got this one. Put it in,and it was showing 15V+ at the battery,but now it shows around 14.2,which is normalish,after driving with it for a while.

Any thoughts/tests I can do myself? It was hard enough getting a replacement from them with the first one,even though when turned by hand in the store you could hear the noise,and I showed them it was only giving 12V(ridiculous,would drop to dang near 11V when fans and lights were on). Same old "but it tests fine on our machine!"

[tractor guy]

I had the same situation with a starter from one of those types of stores. When you hit the key the starter would start spinning and not stop. It too tested fine on their machine until I explained calmly and rationally to the guy how a starter should work, how his machine worked and why it would not replicate the problem. After we changed the test procedure just a little it did what I said it would, and the kid was dumbfounded. I got a new starter.

To make a short story long and try to get back on topic, If all of your electrical grounds in your vehicle are good you may need to add a choke or something to your radio to cut the noise. Or you may be able to get one of the O'reilly guys to come out to your vehicle and listen to the whine.

Joe

[231]

The first thing to do is confirm which direction the noise is getting in through. It's either going to be the power leads to the radio or the antenna...or both. It's an easy test to see if it's only one. Simply disconnect the antenna coax from the radio and see if the noise is still present. If it is, then likely it's getting in through the power leads. Where exactly are you pulling power from? There are filter available along with adding some snap on ferrite beads to the power leads which might knock that out completely. If it's coming in through the antenna, then you have only a few options to solve the problem.

Good luck.

[sparky17]

Other things to check besides the alternator:

I was fighting with alternator whine noise, and it was actually my car stereo amplifier emitting the alternator noise (Changed with RPM, etc). It also picks up and re-emits all kinds of other crap. I turn off my stereo amp when I want to listen to the CB, otherwise it's 7lbs of noise (alternator, fans, window motors, door locks)..

Also, another good test is to listen to the radio while pulling the fuses in your fuseblock to see if any other components are giving you grief.

[petriach]

231,the power is being pulled from the power feeds near the passenger kick panel,it's an ex-cvpi,and there are 2 triple bullet connectors there,fused at the block.(Someone said you drive one too,you seen these?) Ground it connected to the frame with a ring connector with star washer or whatever they are called.

And it's coming from the power leads,you can hear it sometimes when it's really bad through the squelch when the volume is cranked up,usually at idle,seems to stop coming through so much when the engine revs up though past 2000+ rpms

Only RF noise I have is the gosh danged coil on plugs,hate them with a passion.

Sparky,I don't have a audio system in the car,still the normal CV granny radio with oversized buttuns

[hilltop 439]

I had this problem with my mobile setup the problem was that my power lead and ground wire was not insulated well enough and ignition noise was getting between them. What i did to fix this and it my sound crazy was i took two pieces of RG 6 video coax and twisted them together as tight as i could i used the center copper wire of the coax and hooked directly to the battery the positive and negative both. The coax provided a great insulated wire do to the shielding it has and twisting them together prevented any ignition noise getting between the two. It worked for me just trying to throw out some ideas.

[North Texas Mudduck]

these cheap auto stores are nothing but a pain in the butt
oriley autozone advanced auto
either go with a Napa Carquest or take it back to the dealership and have a qualified service tech install a OEM alt back in it

i learned my lesson after about the 3rd time on alts from oriley and autozones
and the whining part
i installed a alt from autozone and it whined and whined to it back got a alt from orileys same whine if not louder
took it out and went to the dealer ship payed like 125 dollars more to have it replaced but i have no more whining

[rslifkin]

I'd blame the rectifier. My Jeep had a whine like that from the alt for almost a year (was there when I bought it), but it all worked fine, so I wasn't worried. That is, until a week ago when one of the rectifier diodes failed and dropped a dead short across the alternator output. Makes A LOT of heat really fast. When I pulled the alt apart and replaced the rectifier, one of the diodes had literally exploded.

[sparky17]

While mucking with my mobile install, I noticed that alternator whine/windshield wiper noises significantly went away when I effectively shortened the ground wire length to the radio.. (foot warmer is grounded).

My radio ground wire is 15' feet, and about 4 feet when I run the foot warmer.. (grounded through the coax shield when using footwarmer).

['Doc]

Do yourself a favor and ground the radio and amplifier to the vehicle's metal with the shortest run possible or practical. Depending on a ground through the feed line is just asking for problems.
- 'Doc

[443 Arizona]

ya rslifkin reminded me of a point, when we use jumper cables, these babies are hard on the alternator diodes,,, if ya know what i mean

[rslifkin]

The key to saving the diodes when jumping is to connect and disconnect without the engine running, that way the alternator doesn't see the sudden shock.