Why are S30 electrics so weak? | The Z Club of Great Britain
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Why are S30 electrics so weak?

Discussion in 'S30 (240Z,260Z,280Z) Electrical' started by Rob Gaskin, Jul 14, 2019.

  1. Rob Gaskin

    Rob Gaskin Treasurer Staff Member Moderator

    I've had an ignition issue this weekend which might be related so the question is why does S30 electrical 'stuff' need the engine running to work?

    Even the indicators don't flash at the correct speed unless the engine is running. I've had this on more than one car.
     
  2. franky

    franky
    Z Club Member

    whats the resting voltage in your battery?
     
  3. datsfun

    datsfun
    Z Club Member

    I think you will find compared to British and Italian cars of same vintage, they are far superior.EXTRA:D
     
    Jimbo likes this.
  4. Jimbo

    Jimbo 1978 260z in yellow

    resistance unfortunately and the distinct lack of relay use.
    you could upgrade it all but its not an easy task if you dont know what your doing.
    upgrading the headlight circuit with relays will help reduce the load on the old system.
    other than that upgrading the alternator would make a big difference especially if you can reduce the diameter of the alternator pulley.
     
    AliK and slaphead like this.
  5. Rob Gaskin

    Rob Gaskin Treasurer Staff Member Moderator

    I have heavy duty batteries fully charged. Upgraded alternators yes (well 60A) but of course I'm asking why the engine has to be running at all. I do have a reasonable electrical knowledge tbh. I have relayed headlights.

    I have upgraded my wipers to Honda too - huge improvement.

    Guys try this - switch your ignition on and try the indicators. Do they operate correctly i.e. flash consistently?
     
  6. MaximG

    MaximG
    Z Club Member

  7. Paul_S

    Paul_S
    Z Club Member

    Mine cause the fuel pump (on a relay) to go off and on when the engine's not running!
     
  8. jonbills

    jonbills
    ZClub Administrator
    Staff Member Moderator

    Mine too.
     
  9. Farmer42

    Farmer42
    Z Club Member

    Ditto. You must have a resistance in the circuit somewhere that stops your flasher unit operating properly. Either that or it's duff! Dry solders on the ignition switch or corroded bulb holders can cause it.
     
    franky and Paul_S like this.
  10. Jimbo

    Jimbo 1978 260z in yellow

    test voltage at the relay and see if your getting battery voltage
    i will be very suprised if you do.
    when the battery is charging off the alternator the voltage must be higher than battery voltage, this in turn is what the circuits in the car are designed to run at.
    when you turn the engine off the voltage will be lower and therefore everything appears to run slower, this isnt a fault its just the way it is.
    age makes it worse with the forementioned resistance and other age related issues.
    modern cars are better regulated (power operating things is regulated to 12v irrespective of alternator output, this is why its not uncommon for modern alternators to output 16volt to charge a battery but not effect the rest of the cars electrics) they are ecu controlled with a myriad or relays sending power along the shortest route so losses are minimalised.
    this can be replicated on old cars but its probably worth just living with the quirky electrics
     
    Rob Gaskin likes this.
  11. uk66fastback

    uk66fastback
    Z Club Member

    Great knowledge Jimbo!
     
    Jimbo likes this.
  12. franky

    franky
    Z Club Member

    The reason to test voltage at the battery, is to see what the 'resting' voltage is, then test along the circuit. to find out where the excess of resistance is.
     
    Jimbo likes this.
  13. Jake RAH

    Jake RAH
    Z Club Member

    My next door neighbours house lights flash on & off when I do that. Is that ok?



    :p :gnorsi:
     
    RawlinSTR likes this.
  14. johnymd

    johnymd
    Z Club Member

    As you know Rob, electric are very very simple. High resistance causes a volt drop so you end up with less voltage at the load. Lessen the resistance in the entire circuit (to and from the load) ( people often forget about the path back to the battery) and your load will work better as it has more voltage across it. Simple.

    As the wiring, switches and connections age their resistances increase a little but eventually all add up to make a big difference.
     
  15. Rob Gaskin

    Rob Gaskin Treasurer Staff Member Moderator

    Thanks guys, that's very helpful. I thought it was just old switches and components.
     
  16. MaximG

    MaximG
    Z Club Member

    It might be worth checking your earth point Rob. You have the obvious one in the engine bay attached to the bolt that holds the break thingy to the inner wing. But there is also probably a lesser known one by the fuel tank which might be worth cleaning up.

    Mike
     
    Rob Gaskin and Paul_S like this.

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