Alternator? | FerrariChat

Alternator?

Discussion in '308/328' started by ClydeM, Jul 3, 2020.

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  1. ClydeM

    ClydeM F1 World Champ
    Owner Rossa Subscribed

    Nov 4, 2003
    10,581
    Wayne, NJ
    Full Name:
    Clyde E. McMurdy
    #1 ClydeM, Jul 3, 2020
    Took the car for gas & coffee. Started fine, warmed up, and at the bottom of my steep driveway I heard a metallic sound which I have been thinking was a shock or spring extending & contracting as the wheels left the pavement & reconnected It's faint & I've heard it for a while. My daily does a similar sound so I wasn't worried.

    Then down the road, the battery light blinked on a couple times. That's a first. The battery is like 4 years old and the alternator was rebuilt like 5 years ago. Battery is on a tender all winter long between limited winter drives.

    The car was idling fine, seemed to be a little off on power though I was driving 1 mile to the gas station easy thinking life if fine. I turned the A/C on. Still no problems.

    After filling the car up, she started right back up, the alternator light went out after the usual slight throttle blip to get it to go out, she started making a sound that sounded like the A/C clutch engaging & disengaging. I turned the A/C off. the noise continued. Sounded like a muffled back-fire more than metallic. Turned the car off & then back on. No noise until I started to move then the noise came back. turned her off & started again. same deal, She teems to be idling at 1K smooth. All gauges read fine. I headed home. Going up my driveway, she lacked power. I thought maybe I was too light on the throttle for the load going up, but the battery light blinked a few more times.

    I just put in a voltage measurer in the cig lighter. At stop, 14V. started, dropped to 10. then she was all over the board at 11v to 13.v. The alternator light came on a few times, but no more odd mettalic noise.

    So can the alternator make that kind of A/C clutch engaging noise? or is it the voltage is too low either causing a cylinder to mis-fire? or causing the ECU to cause a mis-fire?

    Now my 355 started throwing CEL 5-8 lights & codes even though she idled fine. Turns out similar Alternator issues of voltages are messing with the ECU.
     
  2. mike32

    mike32 F1 Veteran

    May 13, 2016
    5,835
    Isle of man- uk
    #2 mike32, Jul 3, 2020
    Engine off should be say 11.7 to 12v. Starting will drop to about 10 v. Then ticking over or above 14v would be good.
    Check the belt tension and if ok see if the alternator free to turn etc
     
  3. mike996

    mike996 F1 Veteran

    Jun 14, 2008
    6,691
    Full Name:
    Mike 996
    #3 mike996, Jul 4, 2020
    With engine off, a fully charged flooded lead acid battery should show 12.6-12.7v. It will show higher if the car has been running recently but that's a surface charge and it will drift down to the 12.6-12.7 level on it's own in a few hours even if you totally disconnect the battery.

    I wouldn't trust the voltage indicator plugged into the cig lighter unless you have verified it - If you haven't, check the V at the battery with a multimeter at various RPM and see how it compares with the indicator. FWIW, remember that charging voltage will change based on the battery's state of charge. IOW, at the same engine RPM, a fully charged battery may show a reading of, say 13.4V while a heavily discharged battery might show 14.5+. The regulator determines the charge voltage based on battery condition.

    The alternator doesn't engage a clutch like the AC compressor does so there shouldn't be any such noise from the alternator itself unless something mechanical has broken/bent - maybe even a partially shredded belt where a piece of it is striking the engine/body. ASSUMING your voltage readings from the cig lighter are accurate, something is amiss in the charging circuit. It could be as simple as poor connections at the battery, system ground, etc. Could also be that the alternator is loose on the mount and 'bouncing' somewhat though I would expect to hear some periodic belt squeal if that's happening.
     
    rjlloyd likes this.
  4. thorn

    thorn F1 Rookie
    Silver Subscribed

    Aug 7, 2012
    3,322
    Tallahassee, FL
    #4 thorn, Jul 4, 2020
    You've checked the alternator belt itself?

    Also, there's no way I would trust voltage readings off the cig lighter for diag. It's not a dependable baseline circuit.
     

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