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How do you check a RRC alternator?

Discussion in 'Range Rover' started by fett, Feb 9, 2010.

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  1. fett

    fett Well-Known Member

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    I want to test my alternator on my 1990 3.9 v8 classic , non serpentine.

    I own a multimeter but am a complete and total novice to electics.

    can anyone tell me how, including setting on the meter, keep it simple please:D
     
  2. gegs88

    gegs88 New Member

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    engine running, multimeter set to dc volts (on number 20 on the dial) then put your probes on the battery terminals. black to - and red to +.
    should be getting about 13v on tick over rising to around 14-14.4 when you rev it
     
  3. Khryztal

    Khryztal New Member

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    your turn for alt troubles then Fett me boy?
     
  4. wammers

    wammers No longer with us, RIP Donater

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    As above, but check it at idle then switch on headlamps to check it under load. At around 1500- 2000 rpm with lights on you should get 14+ volts any less than that it needs looking at.
     
  5. fett

    fett Well-Known Member

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    Thanks guys , I will give it a try on Friday after work!
     
  6. fett

    fett Well-Known Member

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    I was just thinking that a few people on here had said that small missfires and things like that had been caused by a dodgy alt.

    As I have replaced everything else on the car, or its currenly broken I thought I may as well check it:doh:

    Where have you been hiding anyway matey?
     
  7. Khryztal

    Khryztal New Member

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    Been working one hell of a lot. Hows you two?
     
  8. classic kev

    classic kev Well-Known Member

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  9. The Mad Hat Man

    The Mad Hat Man Well-Known Member LZIR Despatch Agent

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    or look in the Q's & A's section where there is a full write-up.

    or take it to Halfrauds coz they will test it for nout.
     
  10. wammers

    wammers No longer with us, RIP Donater

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    That depends on how much is being drawn from the battery by the vehicle. If the battery is fully charged the alternator controller will shut the charge down or raise it as systems are switched on or off, as the case maybe, to maintain a set battery voltage that is sensed by the controller. The maximum you should get is 14.4 or so volts. The alternator does not charge at 14.4 volts all the time or it would boil the electrolite. That is why i say check it at idle then switch on headlamps, the charging voltage should rise with headlamps on to replenish the current being drawn.
     
  11. The Mad Hat Man

    The Mad Hat Man Well-Known Member LZIR Despatch Agent

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  12. fett

    fett Well-Known Member

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    PM'd ya back matey:D
     
  13. fett

    fett Well-Known Member

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    So it should be 14.4 with the lights on? but its ok if its less at idle with them off?
     
  14. Teflon

    Teflon New Member

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    Does the Rev-Counter work properly? does it do strange things like flick to the red-line for no apparent reason? (Especially when you try cranking the engine) Does it just 'trip out' or stop working whilst driving?

    The Rev-counter takes its signal from the alternator frequency. If the regulator 'goes' then the tacho will often just stop working.

    If it does strange things, like flicking to the red line, or wobbling about at steady speed, or dropping out then coming back, it can be pointing to the windings breaking down.

    It's NOT a sure fire test, but if you are having intermittent electrical problems, then the rev-counter can be a good director to the alternator, as it is showing up stuff thats going on while you drive, and as the windings get hot etc, that wont always show up when you test the thing cold, on the drive, and not under the same load or temps as when driven.

    Useful little widget you can get from Halfords is an alternator tester, just clips to the battery, and is essentially a 0-20v volt-meter.

    Using the Multi-meter on 0-20 (or higher) range DC, you CAN test in teh 'dynamic' state, (ie driving!) by extending the test leads through door seal and bonnet gap, and having the meter on the passenger seat.
     
  15. wammers

    wammers No longer with us, RIP Donater

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    Basic answer to that is yes. But is does depend on state of battery charge. If you check it just after starting the charge will be high because there has just been a big drain using the starter. Check the battery voltage with the ignition off. You should have more than 12 volts maybe 12.5. Start up and let the engine idle for a while.Then check it a idle, you should have more than 12.5 maybe 13.8. Check it again with lights on at around 1500 rpm you should have 13.8 to 14.4 depending on battery state. You can check it with ALL the systems running lights, heater fans Etc but you may have to rev engine to 2000 rpm or so before charge balances. And you should still get 13.8 to 14.4 volts. Anything less than 13.8 have a look at brushes and controller.
     
  16. fett

    fett Well-Known Member

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    Thanks for all the input guys , I havent had chance to check it yet as it was dark when I finished work and the wife has me house hunting all the time now :doh:

    There are no symptoms on the rev counter, it seems good its just that the idle is a little lumpy and too low and you can hear a very slight exhaust missfire at idle (only by the tail pipe, yes iI know I am being fussy) and stuart coulnt find out why the idle was low or get rid of the very slight missfire on his last visit.

    As all the ignition parts have been raplaced (several times now) and the fuel economy is now good I just wondered if the alt was the prob , a few people on here have had running issues because of it.

    I have one thing to check though , although the plugs have been changed and checked and cleaned several times I have just invested in new set to fit now its running much better, worried though about the threads on two holes as that fecken mechanic who fecked up my autobox put them in so tight last time I think the threads are right on the edge and I cant afford for those heads to come off! :doh:
     
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