Alternator Chirpping noise?

Discussion in 'Trucks and Trailers' started by inzane, Feb 1, 2014.

  1. inzane

    inzane LawnSite Silver Member
    Messages: 2,476

    I'm having a chirping noise around the alternator area on my Chevy Silverado 2007 (4.3 L V6). I changed the serpentine belt and that helped some( no more squeaking), when the belt was off i spun all the pulleys by hand the alternator pulley has a slight squeak when turned by hand. Now the belt squeak is gone, there is still a chirping.. I spray the center of the alternator pulley with Wd-40 after i start up and it goes a way right away for a short time. It seems like when i get going for a while it goes away for a while. I want to say its the alternator. It seems obvious where the noise is comming from, but still wondering if i should change the alternator, wait.. or try to change the pulley or bearing?

    Does this seem like something would be bad to put off for a little while? Truck runs fine, No other issues other than the noise. I have about 60,000 miles on this truck, its the original alternator.
  2. jc1

    jc1 LawnSite Silver Member
    Messages: 2,030

    Take the belt off and clean the pulley groves with a wire brush. Surface rust and rubber builds up in them.
  3. TuffTurfLawnCare

    TuffTurfLawnCare LawnSite Senior Member
    Messages: 667

    call a local "generator/alternator" repair shop. It sounds like a bearing is bad, just needs replaced. They can be done for a lot less than a replacement alternator. You can do it it yourself, just be careful with the wires, brushes, connections and insulation on the inside.
  4. Landrus2

    Landrus2 LawnSite Platinum Member
    Messages: 4,951

    I would just get a rebuilt.
  5. S&S Lawn ServiceLLC

    S&S Lawn ServiceLLC LawnSite Member
    Messages: 159

    have the alternator rebuilt.Probably looking at a $60 fix at best,WAY better than buying a new one!
  6. Valk

    Valk LawnSite Silver Member
    Messages: 2,711

    You hear it just intermittently offensive? Have a battery shop check your charging system. If no issues, then what? Put up with it or pursue the fix. Also and FWIW, make sure it's not just a tensioner pulley (a cheaper fix) assuming you even have one.
    Good luck. :drinkup:
  7. inzane

    inzane LawnSite Silver Member
    Messages: 2,476

    the mechanic i took it to yesterday thinks the first place to start is the tensioner pulley and a better quality belt. the tensioner does move a bit when the truck is on.. He says it doesn't seem normal for it to move like that. He said if it was a bearing the sound wouldn't just go away. which kinda makes sense. the alternator pulley does make a bit of a squeak when turned by hand, none of the other pulleys do. I've been convinced that the sound is comming from there. Its more than just a little noise. I do get alot of looks my way when i'm driving around. Not the kind of attention i want.

    anyways, this stuff is all new to me. trying to save a little money on fixing a problem that could very much be simple. When i take anything with an engine to a mechanic it seems they want to start replacing stuff before they know what the problem is and it ends up costing me. guess i need to keep searching for a good honest mechanic for the future.

  8. Valk

    Valk LawnSite Silver Member
    Messages: 2,711

    If I'm not mistaken, and I could be...but tensioner pulleys are adjustable (to tighten/loosen belt tension) but static during operation in cars/trucks - in that they do not move dynamically like they do on a mower deck. If it is loose then you would be dealing with an intermittent issue resulting in belt slippage due to a lack of consistent belt tension. What happens when you turn on/off the A/C compressor?
  9. rlitman

    rlitman LawnSite Bronze Member
    Messages: 1,714

    That depends on the vehicle.
    I've seen three systems.

    1) adjustable tensioner: My Subaru has this. You loosen the alternator bolts and the tensioner lock bolt, and turn a screw which moves the tensioner. Then tighten everything to set the new tension. The FSM should give a way to measure tension (usually an amount of belt deflection when pushed or twisted with a specific force at one point), or direct tension measurements (I prefer using my own tension gauge). The tension for a NEW belt will be different than the tension for re-installing a used belt, to make up for expected stretch.

    2) automatic tensioner: My Wrangler has this on the serpentine belt. There is a spring loaded arm that you hold back while installing the belt. Once released, there are witness marks that show if the arm is within the correct range of motion to supply the correct tension. With a new belt that still has the "flat" spots from shelf storage in its memory, the arm may bounce a bit as the belt moves. My Subaru has a similar tensioner for the timing belt.
    In these systems, direct measurement of tension is not recommended. The idler may give an indication of belt stretch, which would indicate need for replacement. Actual running tensions are generally less than found in the previous system, but that's ok. With a fixed idler, initial belt tensions are very high, to make up for the fact that belts stretch, and tensions drop. The initial high tension plays hell on pulley bearings. With an automatic tensioner, that isn't a problem.

    3) no tensioner: I've seen this in newer vehicles. They use an EPDM based belt that is stretched onto the pulleys to supply the correct tension. These require a special measuring tool to check for wear in the belt grooves, as the belts will not show signs of cracking.
  10. Valk

    Valk LawnSite Silver Member
    Messages: 2,711

    Interesting info, thanks rlitman.

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