2012 Audi Q7 No crank but lights work fine and fan activates

[Shimstar]

Hello all,

I appreciate any help i can get from this forum. I have a Audi Q7 3.0 TDI CRCA engine. I have been rebuilding this as a project car which required drivers wing and core support replacing. The car had always started strong upon the first turn when I purchased it and up until recently. the car has been sat on the drive for about 2 months now while I have been working on it with the little time that I have spare. I had used a trickle charger on 2 occasions using the terminals in the engine bay as I was conscious of the battery going flat. Currently, I am getting no crank at all but all the dash lights etc work fine and does not dim when I turn to crank however after about 5 -10 seconds the radiator fans come on and stay on until I turn the ignition off. I initially assumed it must of been the battery so ordered one from Halfords and installed it but this seemed not to help (I did not register it on a diagnostics). While my old battery was out, I trickle charged it to full and deemed it must not be the battery. I have a Autel which is showing voltages at terminal 15 and 30 around 11.7v ( I am not sure if that is enough to send the signal to the starter motor? I have comms with the ECU so I am hoping it is not the ECU. I am exploring whether it could be a relay because of the trickle charger causing issues etc? I did notice when I was fitting the core support a lot of corrosion around a wire that was connected to the main chassis leg on the right side, and I did use tool to hit off excess rust but left it alone after a pathetic attempt. I also wondered if there was a shock security system that may cause this as when I lowered the car from my jack it did land a little heavy and set the alarm off. I am a bit miffed why it would suddenly not crank. Any ideas or suggestions much appreciated.

[Bigdave1230]

Try putting a jump lead cable from the negative terminal under the bonnet or from the battery negative onto a good metal point direct on the engine and try starting it to rule out a bad earth.

[Stevey Y]

8 hours ago, Shimstar said:

Hello all,

I appreciate any help i can get from this forum. I have a Audi Q7 3.0 TDI CRCA engine. I have been rebuilding this as a project car which required drivers wing and core support replacing. The car had always started strong upon the first turn when I purchased it and up until recently. the car has been sat on the drive for about 2 months now while I have been working on it with the little time that I have spare. I had used a trickle charger on 2 occasions using the terminals in the engine bay as I was conscious of the battery going flat. Currently, I am getting no crank at all but all the dash lights etc work fine and does not dim when I turn to crank however after about 5 -10 seconds the radiator fans come on and stay on until I turn the ignition off. I initially assumed it must of been the battery so ordered one from Halfords and installed it but this seemed not to help (I did not register it on a diagnostics). While my old battery was out, I trickle charged it to full and deemed it must not be the battery. I have a Autel which is showing voltages at terminal 15 and 30 around 11.7v ( I am not sure if that is enough to send the signal to the starter motor? I have comms with the ECU so I am hoping it is not the ECU. I am exploring whether it could be a relay because of the trickle charger causing issues etc? I did notice when I was fitting the core support a lot of corrosion around a wire that was connected to the main chassis leg on the right side, and I did use tool to hit off excess rust but left it alone after a pathetic attempt. I also wondered if there was a shock security system that may cause this as when I lowered the car from my jack it did land a little heavy and set the alarm off. I am a bit miffed why it would suddenly not crank. Any ideas or suggestions much appreciated.

Hi try what Dave suggested and if that won't work its probably an immobiliser issue.

Steve.

[Shimstar]

Thanks for the feedback. I will try this out and see what happens. I have ruled out battery as I purchased two different batteries and tried them out, I have also ruled out relay and fuse issue as I have tested them and also tried 2 new relays that are most likely to be issues. I get  comes with the ecu via my autel mk808bt so most likely not the ecu.