Fan run on after ign off - anyone got a circuit?

[Pupp]

One niggle with the Emerald ECU for all its flexibility on fan control is that when the ign is off the fans stop regardless of temperature or soak... anyone got a circuit (perhaps with a timer) that enables run-on if the fans are running when the engine is stopped (always an issue for me when using the car for work by the time I navigate the obstacle course of speed humps to get onto the business park immediately after 20 miles of, err, spirited cross country driving )?

[rev-erend]

Sounds like you need a SPAL fan controller - not wired to the ignotion but instead
to a live battery circuit.

http://www.a1electric.com/spal/faninfo.htm

[jenkotvr]

Yes this is definatly something i would be intersted in fitting.

[Barkychoc]

Why do you need to overcomplicate things?
Just power the fan circuit with a permanent live circuit - if its hot the fans will continue to run till the temperature is reduced below the otter switch temp level.
I remember Ford Fiestas of 1970's vintage did this.

Or have I missed the point?

[jenkotvr]

Barkychoc said:

Why do you need to overcomplicate things?
Just power the fan circuit with a permanent live circuit - if its hot the fans will continue to run till the temperature is reduced below the otter switch temp level.
I remember Ford Fiestas of 1970's vintage did this.

Or have I missed the point?

Sounds good to me as I always leave the ignition on until the fans switch off anyway..

Has anyone done this and documented?

[Ant.]

Barkychoc said:

Why do you need to overcomplicate things?
Just power the fan circuit with a permanent live circuit - if its hot the fans will continue to run till the temperature is reduced below the otter switch temp level.
I remember Ford Fiestas of 1970's vintage did this.

Or have I missed the point?

The permanent live is only part of the solution, the Emerald grounds the fan relay, therefore the emerald would have to also stay live after ignition off.


Pupp, what would it actually achieve though, as the water wouldnt be circulating...

Edited by Ant. on Thursday 17th June 16:48

[Barkychoc]

Ok slightly more complicated but how about wiring the otter switch across the emerald terminals with a relay - so when ignition is on the emerald has full control - but when ignition is off the otter switch is connected across the emerald terminals via a changeover relay (using the contacts that are connected when the relay is not energised).

Connect the otter switch terminakls to fan / ground and you're away.

It will reduce under bonnet temps by a few degrees I'd have thought.

[Barreti]

I have the David Beer half speed fan mod (bear with me on this)

When the kit was built by David he put a wire I could run a live feed from the starter motor into which would keep the fans running after the ignition is switched off.

I did this over the winter and it works brilliantly.

But as Ant says, it very quickly turns off because the water isn't moving, so the sensor cools down and the fans switch off.

Surely unless you move the water around you either have the fans switching off prematurely or staying on for ages because the sensor is sitting in red hot water.

IMHO the work I did over the winter was useful but not essential, I might as well have saved myself the trouble and just lifted the bonnet and left the key in the ignition as I always did.

Edited by Barreti on Thursday 17th June 17:23

[sonnylad]

jenkotvr said:

Sounds good to me as I always leave the ignition on until the fans switch off anyway..

Has anyone done this and documented?

This sounds like the best action to take, as having a fan run on with ignition off is only really cooling the radiator as there is no pump circulating the coolant.

[spend]

The fans power circuits are always live.

I use a heated rear screen relay and a changeover relay (so it is only powered when the ignition is off) in series with the otter switch.

[Pupp]

Not sure the circulation point is entirely correct as the system will still thermo-siphon to some degree, no? I have no otter switch; the Emerald uses the signal from the coolant temp sender...

Thanks for the ideas

[spend]

There is a way with a capacitor to hold the relay closed IIRC.

[rev-erend]

The reason I suggested a pukka solution was that they probably have a timer
so the fans run for a set amount of time rather than rely on the crude system
of running off an otter stch with no water circulation. Way back in the 1980's
none of us trusted these systems as very often they did not switch off for ages
and drained the battery...

[spend]

He might just wants it to fan the starter motor? nothing to do with engine cooling?

[Barkychoc]

Pupp said:

Not sure the circulation point is entirely correct as the system will still thermo-siphon to some degree, no?

I would have thought a little circulation at least - thats how the old back boilers used to work not a pump in sight - though admittedly the hot water tank was usually one floor up.

I would say the key to this is to keep the solution simple - start making it complex and you're asking for trouble IMHO!

Edited by Barkychoc on Thursday 17th June 21:07

[BliarOut]

What about using a self latching relay circuit? That way the first time the fans stop the circuit will go open meaning you can't drain the battery but they will run on still. You could also power anything else you wanted from the latch till it goes open.