Scavenger fan sensor test

[not so old]

Cheers Guys, I feel much better now Yes John it was on thursday that we had all the wire cutting nonsense . I thought we'd never get there, because something was going to blow up Must admit we were on a flat road when it went off(alarm) 105 degrees. the sun was quite warm on the front of the car though.
It didn't go over 110, chris , so that should be OK. I don't know about the hills in scotland though . Better try and minimalise all the gear I take I'm sure I could manage without the washing machine and dishwasher


Thanks Anna

[lizard]

About the 110/115 degree mark is when you need to start worrying.

I have mine fixed on the second threaded hole near the oil filler. Is this where most peeps have fixed theirs This would give a better indication if all TM2 sensors are fixed at the same point.

[Lewy]

All very interesting - I was previously convinced my rad sensor was shot - but now not so sure, perhaps its just never got that hot after all. Still I think I will replace it when I change and flush coolant this Easter if I can get a 12 quid one from Wigan.

I think I will do the scav fan over-ride switch too, especially if it also kicks in the rad fans too (I don't remember seeing this when I shorted the circuit but wasn't looking for the rad fans to operate) as a simple override for extra-ordinary Devon and Cornwall climbs.

My questions are is there a good fit switch to go for for this mod? AND when you put the AC on don't this operate the rad fans too - or are those fans different? In which case you could simply slap the AC on when going up really big challenging hills.

Also had to do a bit of a hike today in van and noticed it really wasn't getting as hot on the TM2 - its fairly windy today has that circulated more air arounf engine bay and block? My sensor is drivers side (inlet) about 3 rocker cover bolts in from front of engine.

[dandywarhol]

Maybe peeps are just fitting to many distactions to their vehicles now - why not just rely on an alarm to give early warning and keep your eyes on the road? There's some vulnerable road users out there......

SORRY MATE!

[lizard]

Maybe peeps are just fitting to many distactions to their vehicles now - why not just rely on an alarm to give early warning and keep your eyes on the road? There's some vulnerable road users out there......

SORRY MATE!

I know, It's difficult watching DVD's as the glow fron the TM2 gauge is very distracting.

[dandywarhol]

[missfixit70]

If you need a boost to your cooling system, go old school, whack the heaters up to full & wind down the windows

[not so old]

If you need a boost to your cooling system, go old school, whack the heaters up to full & wind down the windows

good trick to know. I'll remember that , thanks

[bigdaddycain]

Maybe peeps are just fitting to many distactions to their vehicles now - why not just rely on an alarm to give early warning and keep your eyes on the road? There's some vulnerable road users out there......

SORRY MATE!

It's the vulnerable road users that distract me from flicking switches!

[dandywarhol]

Been doing a bit of scavenger fan testing today (call it a student project and you can work on yer own van in College time )

Removed the fan sensor wire, ignition on - fan didn't come on!
Temperature in the workshop 20 deg. C
Tested the sender resistance - open circuit!
Heated up the sensor with a hot air gun - still open circuit - then noticed a flicker on the ohmeter
Tested "A" terminal of the loom connector for the sensor - 5.1 volts as expected.
Shorted the loom conector - scavenger fan ONLY came on and stayed on for several minutes, even with the shorted connector removed and the ignition OFF
Reconnected everything and applied a heat gun to the sensor - at approx 31 deg.C, the scavenger fan ONLY came on, and stayed on for several minutes, longer if more heat was kept on the sensor, but only with the ignition on (The radiator fans work okay with the A/C switched on)

Conclusion: This is a complex piece of kit. The sensor on the centre console the handbrake only "flicks" on for a second, enough to tell the ECU to close the circuit for a predetermined time. The circuit only works on 4.5 to 5.5 volts (most ECUs do).........don't fer chrissakes ever feed battery voltage to it!
IMHO - leave well alone and don't bypass/mess about with it - it involves more than one circuit.

PS - students bored by the first test..........

PPS - tried it again - this time applied more heat to the sensor - at roughly 50 deg.C the scaavenger fan came on and stayed on even wit hthe sensor disconnected and ignition off for around 5 minutes.

PPPS - students now threatening suicide

[mikeonb4c]

Been doing a bit of scavenger fan testing today (call it a student project and you can work on yer own van in College time )

Removed the fan sensor wire, ignition on - fan didn't come on!
Temperature in the workshop 20 deg. C
Tested the sender resistance - open circuit!
Heated up the sensor with a hot air gun - still open circuit - then noticed a flicker on the ohmeter
Tested "A" terminal of the loom connector for the sensor - 5.1 volts as expected.
Shorted the loom conector - scavenger fan ONLY came on and stayed on for several minutes, even with the shorted connector removed and the ignition OFF
Reconnected everything and applied a heat gun to the sensor - at approx 31 deg.C, the scavenger fan ONLY came on, and stayed on for several minutes, longer if more heat was kept on the sensor, but only with the ignition on (The radiator fans work okay with the A/C switched on)

Conclusion: This is a complex piece of kit. The sensor on the centre console the handbrake only "flicks" on for a second, enough to tell the ECU to close the circuit for a predetermined time. The circuit only works on 4.5 to 5.5 volts (most ECUs do).........don't fer chrissakes ever feed battery voltage to it!
IMHO - leave well alone and don't bypass/mess about with it - it involves more than one circuit.

PS - students bored by the first test..........

PPS - tried it again - this time applied more heat to the sensor - at roughly 50 deg.C the scaavenger fan came on and stayed on even wit hthe sensor disconnected and ignition off for around 5 minutes.

PPPS - students now threatening suicide

Yer making me nervous. OK so I have a direct live 12v feed (via a switch) going to the Scavenger and have left the original feed in place. Since the original supply is also 12v then it ought to follow that it is a separate supply than the one to the ECU, that requires a lower voltage. So the ECU is acting as a sort of relay, simply switching a 12v power supply on or off. You would think, in that case, that there is no danger of feeding 12v into the ECU supply circuit. I'm hoping I've got that right!

[dandywarhol]

I don't know which circuit to are feeding Mike. Most ECUs work on 5 volt circuits whether they're for fuel injection/ignition/gearboxes/blah blah. Feed an ECU battery voltage on the wrong side and you're liable to damage the circuitry. I don't know enough about the intricacies of them to give more detail but the scavenger fan sensor should only be working at 5 volts.

Without sounding more of a pompous prat than I am - I did warn of this a while back but folks with more knowledge of electronics took the risk. I'd be concerned that other circuits triggered by the ECU and linked to it's 5 volt system could suffer and for that reason I'm leaving well alone.

Last year we scaled some long climbs in Europe in high 30s C and the Bongo performed flawlessly. Only heard the scavenger come on a couple of times through heat soak when stopped on motorways. sure the cabin was hot but a couple of Lidl's finest air cooled seat covers were bliss

[g8dhe]

I would support DW comments about the input side of the ECU it will most often be 5 volt powered. However the Fans themselves are relay switched by the ECU, so it is reasonable to play with 12 volts on the relay contacts side.
The two radiator Fans are interesting devices,the diagrams show them as having two sets of brushes each - one set is powered via the ignition switch and controlled by the ECU and the other sets along with the scavenger Fan are connected on the live side of the ignition via there own fuses and again controlled by the ECU, in total there are 4 relays controlling the 3 fans. So that may well explain the oddities you were getting DW with the temperatures and ignition switch, the ECU can override the Ignition switch if it needs to!

Edit later:- Its even worse than above, one set of relays control the +12Volts to one set of brushes and the the other relays control the ground connections to the other brushes so there are lots of permutations - and I am certain it will vary between versions of the vehicles as well to add a bit more spice

[mikeonb4c]

I would support DW comments about the input side of the ECU it will most often be 5 volt powered. However the Fans themselves are relay switched by the ECU, so it is reasonable to play with 12 volts on the relay contacts side.
The two radiator Fans are interesting devices,the diagrams show them as having two sets of brushes each - one set is powered via the ignition switch and controlled by the ECU and the other sets along with the scavenger Fan are connected on the live side of the ignition via there own fuses and again controlled by the ECU, in total there are 4 relays controlling the 3 fans. So that may well explain the oddities you were getting DW with the temperatures and ignition switch, the ECU can override the Ignition switch if it needs to!

Edit later:- Its even worse than above, one set of relays control the +12Volts to one set of brushes and the the other relays control the ground connections to the other brushes so there are lots of permutations - and I am certain it will vary between versions of the vehicles as well to add a bit more spice

V interesting + DWs also. I think from all that that I'm OK with my 12v feed to the power side of the scavenger fan. Must admit, I rarely use it but my excuse is we haven't had a hot summer yet plus (seriously) I avoid traffic jam roads more than ever in the Bongo as I drive for the view and the driving experience more than in a normal car, and that takes me off motorways and out of urban jams whenever possible

I wonder then if there is a simple way to feed 12v direct to the radiator fans on the power side should I wish to (not that I do - I agree with Dandy that a healthy Bongo shouldn't need it and 1st priority should be to check that the rad. sensor is functioning OK)

[dandywarhol]

Okay, I don't have a wiring diagram but the sensor switch has a 5v supply going to it and when the switch momentarily triggers for around 1 second then thats going to be 5v going BACK to the ECU - not directly to the scavenger fan. So you're supplying 12v to the "safe" side (by luck presumably ) of the ECU. Whenever your engine bay gets hot enough to allow the sendor to become a closed "switched" circuit you're going to put 12v down to the "unsafe" side of the ECU - PHUTTTTTT

"Ermmm Bongobits - could I have a second hand ECU please?"

Plausible????