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alternator whine

alternator whine

Postby brownbear [OP] » Feb 22 2011, 8:45pm

finally got my truck running, although it's running like crap now, I now have a pretty loud whine that seems to be coming out of my alternator. I never touched it, it's only 14 months old, it's a high amp 240amp alt. I don't know if I messed something up while trying to get my truck started. I just replaced all the plugs with accel shorty plugs and replaced the ignition coil with a msd. Could a coil cause the alt. to whine? I did do a lot of leaning on the alt. while working on the carb. When the truck thaws out I will have to check my connnections and the belt. It has never whined before until now......any suggestions?
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Re: alternator whine

Postby Alphatonic » Feb 22 2011, 8:53pm

Does it only whine for a short amount of time after start-up?
If so Its probably just a loose belt. That's more of a squeel tho..
Possible oily substance on the belt
Check the ground wire. You may have to make a new ground. Its possible the factory ground isnt sufficent
Last edited by Alphatonic on Feb 22 2011, 9:02pm, edited 1 time in total.
1994 Silverado K/1500 Z71
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Re: alternator whine

Postby Hartski » Feb 22 2011, 8:56pm

Belt could be too tight, too. Or alternator could be just a touch misaligned
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Re: alternator whine

Postby brownbear [OP] » Mar 01 2011, 11:23pm

the whine comes and goes, what i did notice was the batt. gauge would drop to around 10volts. The truck seems to run fine, but the drop in volts isn't good. I got out of my truck and popped the hood, I seen the fuel pressure gauge reading 3psi lower. When I checked voltage with a meter it was 11.7v, which was telling me the alt. was charging the batt. I wiggeled the wires on the back of the alt. and you could instantly hear a different sound of the truck. I checked the voltage and it jumped up to over14v, so I'm guessing it's one of the wires. I changed the wire that went to the battery with a thicker gauge wire. Does anyone know how important that fusible link on that wire is. I don't know if I should put some kind of a inline fuse on that wire or not. The other wire is what I'm concerned with. It's the one with the connector. I have a one wire connector and it seems like when it was wiggled, it made more of a difference. Does anyone know where I can find one of those connectors. Auto parts stores don't sell them.
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Re: alternator whine

Postby Oh that guy » Mar 02 2011, 12:07am

If not the wiring you're already tracing you may have a short, or bad relay somewhere. The increased load on the alternator may be making it whine when the extra load is added. I would think this IF the regulator in the alternator is truley good. This may be the effect, not the cause. If the fusible links have not burned, i wouldn't touch them. Are you saying one is already missing? Voltage on a healthy system is 13.6 minimally. Incorrect wiring can affect the alternator quickly. I'd still pull the alt. and have it tested (free) if it were me. Any pic's of wiring and/or this connector?
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Re: alternator whine

Postby brownbear [OP] » Mar 02 2011, 3:11am

fusible link looked fine, maybe a little old and melted. I removed the whole wire and just ran a new 6 gauge wire. I don't know if I should bother putting a fusible link on or not. It is a 200 plus amp alt. and I'm not sure what size fuse or fusible link to put on, IF I even need one. I don't have a pic of the connector yet, not sure how that will help. You have one thick wire from the alt directly to the battery. Then I have this one wire connector that plugs into the back of the alt. next to where the cable from the batt. goes. From the connector the wire runs into a large loom of wires. It might just be for the gauge inside, but I think it does more than that. When changing the alt. 5 yrs. ago I had a hard time getting the connector off and I ended up snapping off the part that locks onto the alt. I was afriad I wasn't getting a good connection, so I went around looking for a connector, but no one had one. I went to a shop and I guy found one and put it on for me, but it had 3 wires on it and I only needed one, so he cut the other two off. The connector went in, but it never snapped in tight, so I rebuilt the other connector that came off originally and put it back on. Things were fine till I started messing around with the carb, so I'm hoping that a new connector might help.....I would just like to find the connector without having to go to a dealer and spend more money. Advanced has one, but it also has 3 wires on it and I don't know if it will work or not.
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Re: alternator whine

Postby lzn197 » Mar 02 2011, 4:55am

A bad diode in the alternator will cause noise. The 11.7 volts you stated does not indicate it is charging correctly.
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Re: alternator whine

Postby brownbear [OP] » Mar 02 2011, 9:20pm

anyone know where I can buy this one wire connector plug for the alternator? It has 4 holes in this plug with one of them bigger than the other 3. The thing is I am only using 1 wire, but I cannot find anyone who sells the right plug. Everyone I have seen so far has as many as 4 wires on it. Again I only need the one wire, other than cutting off the other 3 I don't know what else to do or where else to look. I even called a dealer and they had the 4 wire plugs. Let me know if you know of any place I can find one......
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