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Starting from ingition key stopped working

Roger Brooklands

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After work one day the ignition key turns the ignition on but not starter was not powered up.  It bump started and I can now start it by shorting the motor feed to the relay pin.

I've checked the starter and it is fine although the relay resistance is only 1.4 ohms and ignition switch replacement made no difference.  No inhibitor relay is fitted

I now find that there are two pin 30 on the switch one has 12v and the one to activate the starter is 0v.  I've checked the fuses and fuse 29 is intact so this would seem to be the connection between the relay plate to the ignition switch.

Where is the relay plate and is there a full wiring diagram for the starting system.  My Haynes manual simply shows battery to main fuse to relay plate to ignition switch.

Any experience of this


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The ignition barrel turns the switch which makes the connection from terminal 30 to terminal 50b but there is no power to that terminal 30 to energise the starter relay.  The other terminal 30 has power which is why the rest of the ignition system works.

I could connect the two 30 terminal together but I am concerned that the extra current will blow the fuse.

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The immobiliser relay should be in slot 11 on the relay board under the driver's side dash but it is not there. 

It is the 12v feed to the switch that lacks power and that is the one that provides the power to the parking lights when the ignition is off so it can't be the immobiliser.

The ignition switch is a two pole four way one with each pole having a separate power feed cable and source. One does the parking lights and starter and the other pole the ignition and related systems.

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Is there a cut out switch on the cluth pedal manual box and  "press clutch to start"

or if DSG is the switch on the N or P not working properly

I believe the inmobilser just cut the fuel but on my 2 Audis TT is a manual clutch to start message

Q3 is DSG P or N to start


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The relay plate is, as expected, under the banks of relays and that looks fine.

However, the only relay in the upper bank is marked EA4 D113-01 382 and this is variously described as Rear lamp tester relay or, on eBay, interior light relay.  I suspect that this relay is not working as the resistance across the terminals is 3M ohms.

Does anyone have a wiring diagram for the relays as these are absent in the Haynes manual?

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It's a transistor driven relay that explains the high input resistance, they come apart quite easily by levering the base.  It probably is for the interior lights triggered by a low amp sensor.

Next one to look at is relay 100!

Thanks for all your input as it makes me explore even more.

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  • Solution

All relays working,  not the ignition switch although the feed to one pole was intermittent  and resolved by tightening the securing nut.

The Haynes manual suggested the cable so I explored the cable at the starter end.  It went into a bunch of cables and when the tie wraps were removed the cause was found.  For some reason the cable was folded into a loop and wedged under the bunch of thicker cable.  The movement during stating rubbed away the outer and then the copper leading to a 1 cm break.  As there was enough cable to splice and solder it back together it is now working properly.

I now need to extinguish the air bar light as I switched the ignition on when the airbag had been removed.😂

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  • 3 weeks later...

An update on the air bag and steering wheel sensor warning lights.

As expected the air bag code was cleared by a code reader (Autel ML629) and was due to turning the ignition on when the air bag had been disconnected.

The steering wheel sensor came up with code 00778 indicating an implausible signal.  Eventually tracked this down to turning the sensor through 360 degrees when the steering wheel was off.  The Haynes manual says to check that the yellow dot is in the circular small window  at the top right of the sensor.  When the sensor was rotated 360 degrees it appeared and the code cleared.  A short drive confirmed that it did not come back so be careful to follow the manual 😀

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