Budget Automotive Multimeter

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  brendanm on 30/11/2019 - 21:58

  +1

  Literally any multimeter should do the job. Just grab one from Jaycar.

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  outlander on 30/11/2019 - 22:12

  +1

  I've gone down this route. With all the electronics in cars, its hard to do. However if you insist, the best way is to get a shunt. Something like this is $4. Wire it in series, then measure the voltage across it. The current going through it will be proportional to the voltage across it.

  For that one, a voltage of 75mv = 30amps passing through. If you measure 15mv, that would be 15/75 * 30, which equals 6amps.
  If you measure 5mv, that would be 5/75 * 30, or 2amps

  There are all kinds of different shunts available, so get the one you think is suited to your needs.

• 

  pegaxs on 30/11/2019 - 22:17

  20A??? that isn't a parasitic drain… With that much drain on the circuit, you could use a thermometer to find it.

  The other thing I would consider is load testing your battery. A lot of people think they have a drain going on, and it's just a battery that is in the final stages of dying.

  Also, go around the car and check all your earthing/grounding points. Make sure they are all clean and tight and all the plugs around relays are connected firm and free from corrosion. same with the fuse box. These are the most common places for electrical leaks.

  • 

    lobsterboyee on 01/12/2019 - 00:09

    I have 0.64A drain when switched off. Battery and alternator are less than 12 months old, alternator is giving the battery 14v when running. Wanted a 20A just for future, in all honesty would only need a 10A multimeter. The joy of a 33 year old Skyline….

    • 

      Cartman2530 on 01/12/2019 - 08:21

      Pretty sure a regular multimeter will do. 640mA drain means something like your stereo/amp or alarm (if you have any of these) is drawing a fair bit of power. To find it, i'd start by disconnecting them all one by one until the current drops down a lot, if its still there start pulling fuses until you find the circuit that is causing the problem. Not many other oem parts on the car would draw that much power while the car is off unless faulty, otherwise the battery would be gone pretty quick.

      has this always been a problem since you had the car or has it just started after you installed something?

      • 

        hawkeye on 01/12/2019 - 09:23

        Good point most radios have 2 power in leads one direct to battery the other to ignition if there arse about who knows.
        I buy these if you can wait a few weeks or handy to have as a spare https://www.ebay.com.au/sch/i.html?_from=R40&_trksid=m570.l1…

        • 

          lobsterboyee on 01/12/2019 - 10:14

          @hawkeye: Problem has only recently started happening. It has an aftermarket head unit and alarm system. After researching this was going to be my first point of call.

• 

  lobsterboyee on 02/12/2019 - 20:30

  So an update, removed all fuses and relays and still had a 0.30 draw. Had me scratching my head going wtf. Then pulled the battery connector to the alternator, gone straight away. So I’ve found the source. Either bad diode in rectifier or incorrect wiring of the alternator.

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  the Unforgiven on 03/12/2019 - 02:19

  If you have acid & other stuff on the top of your battery,
  it will act as a conductor so it will create a circuit,
  so it will then drain your battery.
  Boil a kettle of water & when it is boiled,
  just pour it across the top of the battery & it will clean it

  • 

    lobsterboyee on 03/12/2019 - 08:39

    Thanks for the tip, however the battery is in great nick.

    • 

      the Unforgiven on 03/12/2019 - 11:33

      no worries

      lead acid batteries can die anytime,
      to properly check a lead acid battery,
      you need a hydrometer

      here is another tip,
      if the battery is having a hard time to start or won't start,
      after cranking over the motor (or before),
      take off the battery tops & have a look inside,
      if a cell is bubbling, it is crook

      caution:- gas made from & in batteries can & will explode,
      that is the hydrogen part out of hydrogen sulphide.
      I saw one blow up, acid everywhere, not good

• 

  lobsterboyee on 09/12/2019 - 20:46

  An update. Had the alternator bench tested by my auto electrician neighbour, all checked out. So only logical thing left to do was test the wiring harness with a test light. The numpty who installed it previously had the permanent live onto the L of the plug instead of the S. All is well now.