Wiring challenge

I am "wishing" to have an in-cabin switch to switch the engine bay fans from 6v to 12v as and when I feel like the engine bay needs a bit more cooling than normal. Like during a sprint or during/after some spirited driving.

Their operation and switching (between 6 and 12 volts) is elequently described in the w/s manual, pages c-49/50/51. I think I am looking for resistor 577 and a way to shunt it with a dash switch.
Does any one know where this 577 resistor is?

Maybe I am better of to wire in a shunt to activate the timer relay 300 instead?

any views?

I am "wishing" to have an in-cabin switch to switch the engine bay fans, when I feel like the engine bay needs a bit more cooling than normal.

Simon, the simplist way of achieving what you want, is to short out temp sensor 574 with a relay triggered from a redundant dash switch. You will have to use a relay as the dash switch will not carry the current of the fans. A Lucas SRB522 (15 amp rating) or similar fused relay should surfice. This 574 Temp sensor is the engin bay over temperature switch which will bring on both fans with a full 12v across each. If you want a more detailed discription, just let me know.

John

John, I am glad you replied, some how I thought you would have a good solution.

I do something like that now, but the ultimate solution needs to be ignition controlled too.
For now I just use a 1 inch wire with blade connectors on each end and I use it to short the connector wires to the sensor. Unfortunately at my last event I forgot to remove the link when returning to the paddock and the 12 v fans drained the battery. Not something I wish to do again, doh!

Maybe what I need to do in the cabin is to ground the RHS input to relay 300 (via a relay) to simulate switch 574 being closed?

Now I have looked at the diagram again, i am completely confused.
- 575 ONLY lights the lamp, yeh? so no point doing anything to this.
- 233 energises the RHS of 300, and does something to the timer.... maybe holds it high/low??? and allows current to flow through 577, through the RH switch of 300 and to 576 then through resistors to the fans, but dont know what this acheives ??? 6volts only i thnk.

Now I have looked at the diagram again, i am completely confused.
- 575 ONLY lights the lamp, yeh? so no point doing anything to this.

I think you will find I said 574. This is just a quickie, I am going to reread what you have just posted.....watch this space

I do something like that now, but the ultimate solution needs to be ignition controlled too.

All you have to do is feed the relay coil with 12v after ign, so when you switch off the ign the relay will drop out and the short across 574 will be removed, remembering of course that if the temp in the engin bay is still above 90`, the fans will still run until the temp drops.
If you can let me know what switches are redundant at the moment, I will see if there is one which is fed with 12v after ign
Dont get bogged down in the circuitry, it is a dead simple mod, this pic should help.

I have redrawn the relay mod as the original could have confused, as the contacts appeared to be closed on the scanned pic, clearly the contacts should be open and would only close on switching on from the dash

John

Simon, The fan speed resistor is located behind the radio on the passinger side. If you remove the side cover, then connect the switch shorting out the two wires, the rear fans will run at 12 volt when the engine compartment or oil, reaches temperature.

See attached diagrams.

Andrew

when I feel like the engine bay needs a bit more cooling than normal. Like during a sprint or during/after some spirited driving.

That'll be all the time in YOUR case then won't it!

Maybe ??
But a nice option to have/use.
Thanks Andrew.

Maybe ??
But a nice option to have/use.
Thanks Andrew.

I can visualise the sheepish expression as you said that