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Testing for bad battery connections and bad earths...

  • 13-11-2014 11:02pm
    #1
    CountyHurler
    Closed Accounts Posts: 8,657 ✭✭✭


    Hi there,

    My brother recently had a problem with his car... He got the clutch done and "coincidentally" shortly after there was a problem with the alternator not recharging the battery.. Turns out the guy had left the earth connection from the gearbox loose..

    But this got me thinking.. Everybody I've seen online normally suggests voltage drop testing to identify such a fault... But if you have a no start condition, why dont people just run their jumpleads (which most people already have)... red cable from battery + to starter +, and black cable from starter - to battery - .... (basically running parallel connections for both connections).. then try to start the car..

    Wouldnt this be a quicker way to identify the connection fault?


Comments

  • #2
    dieselbug
    Registered Users, Registered Users 2 Posts: 1,104 ✭✭✭dieselbug


    Voltage drop testing is a excellent way to diagnose and isolate a fault in a circuit. Moving along the circuit until you find where the drop takes place.

    Using the jump leads will confirm there's a problem, but where?


  • #3
    CountyHurler
    Closed Accounts Posts: 8,657 ✭✭✭CountyHurler


    I know what you're saying DieselBug and I agree using the cables will not identify exactly where the fault lies... But I guess I've seen where mechanics go through the process of changing battery, then changing alternator, then possibly changing starter....And only then tackle the possibility of there being a problem with connections / cables...

    I would have thought that it would have been an useful and easy FIRST step... Car arrives with no-start condition... Straight away, hook up the parallel cables (as described in my original post) and then
    i) if the car starts, then you have an excessive voltage drop somewhere along the connections/cables and you can move on to a more granular voltage drop test..
    ii) If the car still does not start, then you know that the problem is not caused by connections/cables and you can move on to battery/alternator/starter troubleshooting.


  • #4
    dieselbug
    Registered Users, Registered Users 2 Posts: 1,104 ✭✭✭dieselbug


    CountyHurler wrote: »
    I know what you're saying DieselBug and I agree using the cables will not identify exactly where the fault lies... But I guess I've seen where mechanics go through the process of changing battery, then changing alternator, then possibly changing starter....And only then tackle the possibility of there being a problem with connections / cables...


    Like this for example




    http://www.boards.ie/vbulletin/showthread.php?t=2057323345

    While attempting to start, first check the voltage at the battery. If that's ok check the voltage at the starter. If it's still ok then suspect your starter.
    Ten minutes max.

    Presuming there'a feed to the solenoid of course.


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