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Thread: Low voltage at starter motor solenoid – hence no start

  1. 16th March 2011, 07:48 PM #1
    pibby
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    Low voltage at starter motor solenoid – hence no start

    1998 disco petrol running 14cux

    Getting around 9.5 volts at the solenoid. Turn key – nothing. Run wire with 12 volts to solenoid and starter kicks into action.

    So trying to backtrack where the feed to solenoid is coming from – disappears into a bunch of wires above the auto. So what I can visibly see is a wire which goes out the drivers side back to pins 14 and 40 on the ecu but these are earths. The other wires I can see go out via the passenger side to a connector next to the washer bottle and then off to wherever from there. I tested each one of these wires pins on the connector and was unable to find 12 volts on any of them.

    tested the inhibitor switch and its output reads 0 volts where it needs to be and approx 9.6 when in gear. So appears to be working except for the low voltage. The solenoid appears to be supplied from the output of the inhibitor switch. So where the bloody hell does the 12v come from to supply the inhibitor switch.

    The car once was a manual but has been converted to auto but surely I should still be able to locate the 12v supply to the inhibitor switch so I can tap into it with a new supply???

    Spent way too many hours trying to find it so am hoping for a lead in the right direction. Worst case scenario – if I run a new supply to the inhibitor switch which is powered when ignition key is turned to start the car will this cause any other issues?

    Had an unexpected roadworthy to do as rego had lapsed by 1 day over grace period so car been off the road last few days and now too much stuff having to go onto the backburner. Just hotwiring like I have done fails the roadworthy, it must not be able to be started in gear. Geez – not happy. Not at all.

    Any suggestions?
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  2. 16th March 2011, 08:01 PM #2
    bee utey's Avatar
    bee utey
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    Do the same as every other person in this situation does...get a relay, run it off the 9.5 volts and use it to switch battery power to the starter.
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  3. 16th March 2011, 08:17 PM #3
    pibby
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    ah, grasshopper....

    very good. was focused on trying to put things back to normal but completely overlooked the obvious/simple solution.
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  4. 17th March 2011, 05:22 PM #4
    pibby
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    Wired up a relay and what do you know, can’t get the starter to turn. connected the wire (which normally goes onto the solenoid) to trigger the relay but the 9.5v it is carrying drops to 0.5v when connected to the relay and my guess is it is not enough to trigger the relay.

    Tried 2 other relays and jury rigged them plus my original relay and can get them all to work off a full 12v.

    So why are the volts dropping?

    Still like to work out where the 12v feed to the inhibitor switch comes from – anyone know. At least it gives me a backup if can’t figure out why the volts are dropping.

    Taking it back in for roadworthy in the morning so hoping to get it sorted.
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  5. 17th March 2011, 05:52 PM #5
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    bee utey
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    Run a wire direct from the starter wire at the ignition lock to the inhibitor switch. Hopefully the inhibitor switch is OK or you might just have to bypass it and hope the roadworthy inspector doesn't spot it.
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  6. 17th March 2011, 06:21 PM #6
    pibby
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    any hint on which wire it would be or how to identify it? although....

    have tested the inhibitor switch works by checking supply to starter solenoid had power in p and n, but nothing in any gear. so really i could just find any supply which has 12 volts with ignition on and 12v with key turned to start then use this to feed the inhibitor switch. as i know it works, it will look after ensuring car doesn't start in gear.

    still hoping someone would know where the feed is that goes to the inhibitor so i can just tap into that rather than running a cable in underneath the car and trying to splice it in. not a lot of room under there.

    thanks for the replies bee utey.

    inspector already failed as starts in gear so have to fix this properly as it's on his list to check.
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  7. 18th March 2011, 07:22 AM #7
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    According to my copy of RAVE the inhibitor switch is in the t-bar selector under the console cover. You should be able to find the starter operating wire here, and feed 12V to the inhibitor to see starter operation, then hot wire from the key switch harness direct to the inhibitor.
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