No so urgent

[karlos]

back to the engine bay induction fan, that runs off the sensor by the hand brake.

I reported a while back it came on after a short journey - anyway that's not the prob.

As Daddyc said with the ignition on "if you unplug the sensor after a few sec's it turns on" - tested this was ok!

Now then - now when I unplug the sensor as above does not come on - having install a switch in one wire to simulate the sensor being removed it make the circuit go open circuit this doesnt work?

So Now I'm with fan will not cut in via sensor of via switch and no it isnt because switch has added a risistance or anytthing like that - when the switch brakes the circuit simulating removal of the sensor it is open circuit so fan should cut in as previous. (fan would not work before fitting switch either, I put the switch in to reassemble van for use!) Although fan work did once recently when I removed sensor after a long drive - which made me think maybe eng bay ambient switch is in series with maybe engine temp switch so the fan wont cut in with a cold engine! "seems like an irratic intermitant number"

Any way I seem to have an intermitant fault with the standard wiring/fan as It works one minute and not the next - It is not the sensor because removing it to test opperation.

Even if the fan is controlled via ecu I suspect there is a relay somewhere? as most ecu's dont handle higher current applications. - I have no diagrams and dont want to get into opening up the loom or ripping the dash out - crawling around van with the mulit meter testing colour coded cables from end to end etc.... ( I suspect if it has a relay maybe it's on it's way out) The fan has run so I doubt it's electic motor related - the sensor is void as I know it cuts with it removed! (and I have used the switch in both positions) I'm only braking one wire not linking both so I cannot create a circuit via the switch with the sensor removed!

Any locations for specific relay and fuse - the fuses under the bonnet test ok! ?

Thanks

[dandywarhol]

Don't claim to know the exact science behind it but at certain temperatures the fan will ONLY come on if the circuit is made for a split second - that way the fan is triggered via the ECU and runs whether it's plugged onto the sensor or not.

Maybe I didn't explain it well enough the last time you asked Karlos

[g8dhe]

The relay is in the position shown here as B6-06 by the battery, row nearest the bulkhead, and on the right hand end. Click the thumbnail for large size image.

The relay is fused by the 30Amp ADD FAN (in the larger fuse box), and driven by the ECU so you can expect many factors might come into play before the ECU decides to operate it.

[karlos]

Thanks for the pic, I will have a poke around sometime in the light - I recall the fuse boxes under the bonnet but not the relays - I have indicator relays by the driver accelerator pedal.


Dandy I did understand last time, a flick of voltage etc. I suspect the sensor -is can not remember the term negative colestant? as the temp rises the resistance drops finally low enough for preset value in the ecu enough to send a feed to a relay ecu blah blah.

The truth is I need to get a manual - although I'm told it doesnt come with wiring diagrams - wierd as all the proper work shop manuals I have do and they are for jap machinery "not imports in the same sense i.e they were meant for uk market" I'm trying to get any issues addressed without spending additonal money as my other automotive projects are finacially taking over my life.

[missfixit70]

Wiring manual in the club shop - http://www.igmaynard.co.uk/bongo/mercha ... tm#Manuals

[karlos]

I recon I shouldnt have bothered with the auto/manual overide fan switch.

Whilst messing about after a bit of a drive hence temp in eng bay - with igntion on, engine off the switch open the fan cut in. the water/eng temp on my gauge dropped. So I kept fiddling - removing the sensor (going open circuit) would not bring fan on with engine running. Tested again worked on ignition - I now presume the fan/sensor circuit is ok.

This experiment has been a waste of time!

It seems the fan does not just look for a break in the circuit(as dandy mentioned it is not just a simple this or that makes it work,- it may look for a specific ohms reading or what ever but it must have other viariables involved i.e engine temp) -

using a switch to either run off sensor or trick it into thinking it has been removed does not work properly.

Whats more once the the switch breaks the circuit enabling the fan when you turn the igntion off and remove the keys the fan keeps running until you switch it back to auto(sensor) and turn the igntion on and off again.

I conclude this is dodgy as if it has more variables and it involves the ecu might cause problems with the black box doing funny things at the wrong time. So I'm going back to standard.

I have my temp gauge and my coolant level alarm - that will have to do for towing my precious around, will have to get break down cover for trailer and bongo if the worst should happen - Touch wood all is well at the mo!

Well some ones got to do these things I supose, I rather be the one who tested the ideas than talk about thing I'd never done.

[mikeonb4c]

Phew - glad its sorted, but I'm confused. I fitted a new feed direct to my scavenger fan via a switch and fuse and it works fine. I didn't go anywhere near the ECU thingie - just ran a fresh 12v supply straight to the fan. Its proved to be an excellent mod. and keeps the engine bay cool(er) when things get hot

[dandywarhol]

If you have time to read through some of the posts I've put up over the past few years you'll read that I came to the same conclusion a while back Karlos.

If you're really determined to have the scavenger fan on manually then do as others have done and feed the fan directly from a relay and manual switch. That way you'll avoid the potentially fatal (for the ECU) situation of putting battery voltage to the "black box".

You'll also read that I personally think its a waste of time devise a system to operate the scavenger fan manually. I've towed a trailer with two 210 kg motorbikes and the Bongo laden around Europe/towed over the Pyrenees/run through west/east Germany for 8 hours virtually non stop in high 30/40 deg. C and the engine has never overheated. During these temperature the fans click in and out when requested by the designers. If the cooling system is PROPERLY maintained, the system works just fine - unfortunately millions of yen of Mazda research and development cannot overcome owners complaicency and mechanics ineptitudes.

If someone needs to over ride something which works perfectly well by design then something must be wrong in the 10 year old + system somewhere I.M.O.

I'll now sit down and await the

[mikeonb4c]

What moi?

Oh go on then:





But seriously, it keeps my passenger compartment cooler (the main reason I did it), plus I don't need to worry whether the system as designed has decided to go AWOL through old age. If that were to happen, my engine bay could be happily cooking itself without me knowing.

Also, its another switch with a (blue) light on - and thats important to me as I don't get out much and I have not the skill or will to do proper pimping

[dandywarhol]

I've got one wee blue led switch thingy on my dash and that tells me how long the glowplugs are glowing for - and more importantly it switches them off! Thats the extent of my pimping - on the van that is

[mikeonb4c]

I've got one wee blue led switch thingy on my dash and that tells me how long the glowplugs are glowing for - and more importantly it switches them off! Thats the extent of my pimping - on the van that is

I liked that

[karlos]

I think I just got a bit over concerned, when I first got the van overheating via hosesleaking, cracked heads and head gaskets seem to be a commonly reported problem. I have a good amount of mechanically sympathy so I hope I should be ok now!

I plan to tow next year,- something similar to a caravan with a very/very light way car inside so I wanted to avoid any potential problems before hand.

I realised the simplest route would be to just operate a relay to pull in the fan - but as removing the sensor was suposed to cut the fan in - seemed simple to brake the circuit with a switch.

I probably wont bother with any mod to this fan system now - I tackled several tasks within the first two weeks of gettin the van, made sense while I took it to bits to carry out all the tasks at the same time.

Starter Contacts, Silicon hoses, Alarm with servo to make central locking remote, a accurate deg c gauge for water temp, my own coolant alarm, all works spot on, (fan switch now void)

[bigdaddycain]

I have a switch which breaks the fan circuit, (thus activating scav& rad fans) I have rarely used it, but it's there if i ever need it. (if the sensor fails). I have only ever activated the switch whilst the vehicle is in motion,and under heavy climbing load. I have never overheated thankfully, but thought it a practical (and quick) fix IF my gauge ever does nudge the red... There is a post elsewhere on the forum where a coolant leak led to a dramatic and rapid increase in temps, and by the time the poor owner did pull over it was too late and his head was cooked, activating the fans would not prevent this scenario, but for the sake of a flick of a switch there wouldn't be any harm in trying to head off as much excess heat as possible.

[mikeonb4c]

I have a switch which breaks the fan circuit, (thus activating scav& rad fans) I have rarely used it, but it's there if i ever need it. (if the sensor fails). I have only ever activated the switch whilst the vehicle is in motion,and under heavy climbing load. I have never overheated thankfully, but thought it a practical (and quick) fix IF my gauge ever does nudge the red... There is a post elsewhere on the forum where a coolant leak led to a dramatic and rapid increase in temps, and by the time the poor owner did pull over it was too late and his head was cooked, activating the fans would not prevent this scenario, but for the sake of a flick of a switch there wouldn't be any harm in trying to head off as much excess heat as possible.

attaboy - i like your style