Audi B3 ignition relay / ignition on issue ?

mk1mistry · 08-07-17, 06:14 PM

Afternoon Gents,

I've got a B3 90 QS with an S2 engine,

It seems to have developed an issue where the ignition stays on,
When the vehicle is running the cooling fan turns off when the key is removed, but the engine will continue running.

Has anyone had this issue ?
Also where is the ignition relay so I have a starting point to check,

Thanks

fourringsrus · 08-07-17, 08:17 PM

I had a 1989 B3 90 which did similarly odd things, my first point to check was the ignition barrel switch, which turned out to be the source of the issue.
The switch was worn/damaged from age and was a simple and cheap fix, this should be the first place to check in my opinion.
If that is non confirming ,I think your ignition relay is in the fuse box under the offside corner of the windscreen in the engine bay, but somebody more knowing might correct me on that one
Good luck
Stuart

msh · 09-07-17, 09:34 PM

I agree with the thoughts about ignition switch, because symptoms point at that direction. There's no such a thing like "ignition relay", there's only X relay, and it works fine, that's why rad fan stops upon turning off the ignition - X relay turns off X group of consumers, including fan relay thermo switch supply.

mk1mistry · 11-07-17, 07:53 AM

I thought it mite have been the switch but apon unplugging the switch the fault still occurs,

If there is no ignition relay is there any way that the ecu will get power without the switch ?

msh · 11-07-17, 09:55 AM

Does it have some aftermarket immobilizer?

mk1mistry · 11-07-17, 10:06 AM

No, not that I am aware of, i think I will have to pull the dash out to see if there is any broken wires

msh · 11-07-17, 02:23 PM

After looking at the schematics my conclusion is that the only way where something could happen is between ignition switch and fusebox, in the dash wiring harness - for engine to be running it doesn't just require for ignition power to be provided to ECU - fuel pump relay coil also receives power from group 15, therefore ignition power is already at the fusebox.

fourringsrus · 11-07-17, 06:10 PM

Maybe I didnt mean relay, but some kind of power supply in the fuse box is what I was getting at

08-07-17, 08:17 PM	#2
fourringsrus Grown up member Join Date: Feb 2011 Location: Ashford Kent Posts: 468	I had a 1989 B3 90 which did similarly odd things, my first point to check was the ignition barrel switch, which turned out to be the source of the issue. The switch was worn/damaged from age and was a simple and cheap fix, this should be the first place to check in my opinion. If that is non confirming ,I think your ignition relay is in the fuse box under the offside corner of the windscreen in the engine bay, but somebody more knowing might correct me on that one Good luck Stuart

09-07-17, 09:34 PM	#3
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	I agree with the thoughts about ignition switch, because symptoms point at that direction. There's no such a thing like "ignition relay", there's only X relay, and it works fine, that's why rad fan stops upon turning off the ignition - X relay turns off X group of consumers, including fan relay thermo switch supply.

11-07-17, 07:53 AM	#4
mk1mistry Grown up member Classic Audi Club Member Join Date: Nov 2011 Location: Essex Posts: 159	I thought it mite have been the switch but apon unplugging the switch the fault still occurs, If there is no ignition relay is there any way that the ecu will get power without the switch ?

11-07-17, 09:55 AM	#5
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	Does it have some aftermarket immobilizer?

11-07-17, 10:06 AM	#6
mk1mistry Grown up member Classic Audi Club Member Join Date: Nov 2011 Location: Essex Posts: 159	No, not that I am aware of, i think I will have to pull the dash out to see if there is any broken wires

11-07-17, 02:23 PM	#7
msh 4 ring whore! Join Date: Jun 2008 Location: Rucava, Latvija Posts: 3,816	After looking at the schematics my conclusion is that the only way where something could happen is between ignition switch and fusebox, in the dash wiring harness - for engine to be running it doesn't just require for ignition power to be provided to ECU - fuel pump relay coil also receives power from group 15, therefore ignition power is already at the fusebox.

11-07-17, 06:10 PM	#8
fourringsrus Grown up member Join Date: Feb 2011 Location: Ashford Kent Posts: 468	Maybe I didnt mean relay, but some kind of power supply in the fuse box is what I was getting at