Scavenger Fan Override?

[Gasy]

I was on about
If the engine caught fire
The fan would come on and fan the flames
Surely that's not a good idea / design

I once had a van catch fire in the middle of the night
Electric prob smouldered someone see it smoking from headlight
Kicked headlight in to try and stop it
And up it went as more air got to the smouldering electrics

[JoeC]

Use a hair dryer to heat the sensor.

[Fassi]

I was on about
If the engine caught fire
The fan would come on and fan the flames
Surely that's not a good idea / design

I once had a van catch fire in the middle of the night
Electric prob smouldered someone see it smoking from headlight
Kicked headlight in to try and stop it
And up it went as more air got to the smouldering electrics

Ah. This is a very good point.

[Simon Jones]

The Bongo is not renowned for spontaneous combustion but if some yoof decides to torch it for you, it's going to be wrecked with or without the addition of a fan to speed things up.

[Gasy]

Yes but things can smoulder for hours and it's only when extra air blown over it that it combusts
Just like bear grills starting a fire

The fire brigade said my van had been smouldering for ages inside the ecu / electrical controll box tucked up behind the glove box
Before it combusted

[Simon Jones]

Best park it out of the wind then

[petebee]

I have had no problems overriding my scavenger fan with out the use of a resistor,but the LED on the 12 volt switch doesn`t light.the voltage measures 5V.Anybody any ideas if there is a switch available that will light at that voltage?

[Fassi]

Latest news. If I park the Bongo and the temp gauge is just under 84 and I leave the switch on. The scav fan comes on as I stand by at the side of the road, key in hand, anywhere between 10 seconds and several minutes. I guess the heat soak has taken it to 84. It will only do this once though and last 5 minutes. So I still need to find out if the scav fan will come on everytime 84 is hit or if it is just a one time 5 minute blast as soon as this temperature is recognised by the ecu and needs a reset by the ignition key being used.

It makes no sense that my 400 ohm resistor would allow the scav fan to come on with no ignition, but gasy and the1andonly have a smaller value resistor and it does not do the same. The drawings show the ADD fan connected to the battery so power is always there. So everyone's has the potential to come on when the ignition is off depending on what the ECU sees?

Maybe the sensors are having different values in relation to heat. I've not checked mine as yet.

ps. Just to remind. If my temperature is 83 or lower. The fan will only come on with ignition AND will not latch for 5 minutes. Just normal on/off operation.

[Fassi]

Think I'm repeating myself so will calm down a bit. oops.

[Tony x]

Fassi
Our override switch has a 400 ohm resistor (well, 2 x 790 ohm in parallel) and will come on if the engine is warm, ignition is off and you press the override switch. It will come on for around 5 minutes. However, and to complicate things, it will only do this for a while after switching the ignition off and removing the key.
I did notice that around 5 minutes after removing the key, I can hear a click, presumably a relay. I tried the override once, just after hearing the click and it didn't make the fan come on.
I've not thought too much about how it works as it appears to work when needed.

Gassy
Regarding the fanning the flames point, I guess you could probably find some kind of thermally sensitive connector (like you get on a kettle) that would cut out the fan if it got too hot.