Sierra Ignition Switch Power cuts to Aux 1 on Crank

[Jake Gully]

I'm losing power on aux1 when I crank the engine over, but this does not seem to affect power to Aux 2.

Is it likely a faulty switch?

I want to run my Emerald ECU Pin 11 from Aux 1 and then the ECU Relay supply to Pin 28 (triggered from Aux 2).   This should allow my cooling fan relay to keep running until lower limit is reached, provided the key remains at position 1.

Works fine if I run a permanent feed to Pin 11, or join 11 and 28 to Aux 2.

What have others done here?

[richyb66]

Use Aux 2 to trigger a dedicated relay that feeds 11, 28 and also power the coil packs and injectors. This is how my Emerald is wired on my Rover V8.

Attached file shows how I wired Emerald on Rover Vitesse (very similar to my car).

Rover Vitesse Main Relay Wiring (1).pptx

[Jake Gully]

12 hours ago, richyb66 said:

Use Aux 2 to trigger a dedicated relay that feeds 11, 28 and also power the coil packs and injectors. This is how my Emerald is wired on my Rover V8.

Attached file shows how I wired Emerald on Rover Vitesse (very similar to my car).

Rover Vitesse Main Relay Wiring (1).pptx 50.48 kB · 0 downloads

Thanks Richy, that's nice and clear.   The inertia switch is also a great safety addition.

I run my fuel relay switched by the ECU Pin 20 provides switch to earth to control the pump, but could easily add an inertia switch in line and will see what I can source.

 

I can run Pin 11 from Aux 2 and use Aux 2 to trigger the ECU power to Pin 28 and this does work, but does not allow the cooling fan to continue running when I switch back to position 1.   Not in itself a huge issue, but also annoying that the ECU shuts down, as I have to turn ignition back to Aux 1 to crank the engine - at least until I get my start button wired in to the lower dash.

 

Oddly, neither pin 4 or pin 6 on my ECU provide the earth switching for ECU or Cooling fan relays, though both relays work if I manually ground them.     I have tested and have a solid ground for ECU pin 29 and 30, so this may have a fault or config error with the ECU which I need to pick up with Emerald.

 

It's all a bit of a learning curve and new area for me, but I am getting intimately acquainted and the snagging list is getting shorter, slowly!
 

[Jake Gully]

OK, I have rewired pins 11 and 28 to the output of the ECU relay (R5) - this relay is now triggered from Aux 2.   Works and runs fine, but still does resolve my issues with the cooling fan or relay control....  Will have a chat with emerald next week.

[IanS]

Dropping power to aux1 dates back to cassette tape deck audio systems. When cranking the volt drop caused the auto-reverse to partially activate and tangle the tape.

[richyb66]

I wouldn't worry about the fan not running with the ignition off. If the engine isn't running, then it isn't got any hotter.

My fan operates like this, Rover 4.6, Cortina Coolman rad. Never had any overheating issues.

[Jonty Wild]

8 hours ago, richyb66 said:

I wouldn't worry about the fan not running with the ignition off. If the engine isn't running, then it isn't got any hotter.

My fan operates like this, Rover 4.6, Cortina Coolman rad. Never had any overheating issues.

Err it could be a problem because if the coolant isn't circulating the engine could continue to get hotter without the fan going, Are you sure that isn't working? i.e. does it come back on at all, even say after a couple of minutes?

[richyb66]

Once the engine is switched off, it's not generating any more heat and the water isn't being circulated. Having the fan on will just dissipate the residual heat a bit faster.

If it's a massive problem, then the fan relay needs to be controlled either without the Emerald or with an additional temperature sensor.

[Jonty Wild]

Yes you are correct there is no more heat going in, but equally no air cooling.  I have had several cars in the past, e.g. Ford Capri, Ford Orion and I think my Audi Coupes (probably others too) plus my Robin Hood 2B, when the fans often came/come on a few seconds or even minutes after the engine had been turned off - sometimes several times.  This suggests that the temperature at the switch had risen enough to turn the fan on again, and I have certainly had cars that boiled over after stopping and, although running hot, not while running (usually because of a fault).

[thespannerman]

Always thought of it as basic safety. You don’t want the fan turning on when working in engine bay with ignition off. Fans bite