Scavenger fan.

[windywatson]

Hi Guys,

Recently fitted a switch to over ride the the temperature sensor that activates the scavenger fan. Why do this you ask? Well wanted to be able to cool the engine bay down quickly once parked up after a long distance run. I find cab area is gets very warm once stood and the heat rises. Great in winter not so good in summer and my Chocky bars go all soft when left in the cubby hole in front of the gear shift. Any way I digress, the question is this. Why should my alternator charge light come on & flash when I run the fan. The warning light for the exhaust temp lights up and flashes which is what I expect as the system thinks it's warning of an over heat.
At first I thought that is must be the amount of load being put on the electrics by the fan & the alternator couldn't keep up. However, I can load the electrics with full lights, heater fan flat out, air con on & fans kicking in and out and that doesn't bring the charge light on! So I've switched every thing off and tried it, and it only need that one fan on to make the charge light come on and flash.
Of course I can switch the engine off and run the fan and this doesn't bring up any lights except the exhaust temperature light which is expected. But surely that one fan can't be exceeding the total load of all other stuff on it's own could it?

Any Ideas?

cheers

[missfixit70]

Are you sure that's not the scav fan warning light? is it the pic of a coil (that also shows the glow plugs are working) it's showing there's a fault in the scav fan circuit (as described on page 92 of the handbook).
How have you wired the switch?

[missfixit70]

http://www.igmaynard.co.uk/bongo/forum/ ... ht#p449567 may put you mind at rest (or not )

[windywatson]

Are you sure that's not the scav fan warning light? is it the pic of a coil (that also shows the glow plugs are working) it's showing there's a fault in the scav fan circuit (as described on page 92 of the handbook).
How have you wired the switch?

Thanks for the feed back on this. I tested the circuit to see if I could get the fan to work by basicly shorting the 2 wires that are plugged into the sensor together. As this worked I assumed it had simulated the sensor being hot and compleating the cuircuit. So all I did was fit a switch across the two wires.

I'll check what the hand book has to say. Could be that the system is seeing the dead short across the sensor as a fault.

Cheers

[jaylee]

Did you use a momentary switch?

[windywatson]

Did you use a momentary switch?

No, the switch is permantly made as long as I leave it switched.

[missfixit70]

Have you tried switching it momentarily?

[dandywarhol]

As others say, the sensor is a momentary trigger to the ECU - what you're doing is confusing the ECU and it's going haywire - mess about with it and it'll cost you an ECU - you'll be a bit hotter under the collar then...................

[Northern Bongolow]

[petebee]

I've done the same as you, short cicuited the sensor with a switch.I always switch on the scavenger fan permamently when towing,not had any problems apart from the switch LED doesn`t light I think because ther's only a 5 Volt feed.

[mikeonb4c]

I fitted a complete new supply from the battery to fan when I modded mine. No probs in 4yrs of use. Irishmans luck maybe

[dandywarhol]

I fitted a complete new supply from the battery to fan when I modded mine. No probs in 4yrs of use. Irishmans luck maybe

No, good sense - that way you aren't interfering with the ECU.