Radiator Fans-over-ride switch

[Peter2414]

Thanks to the great deal of information posted by members (I realy am most grateful) I have fitted an over-ride switch by cutting one of the wires from the sensor in the block and feeding it to an on/of switch. The part I can't get my head around is "leave it in the "on" position when switching of the engine". By doing this the fans keep running even when the engines cold. "I am extreamly confused" of Dorset. Its not a problem as I just switch 'em off !!! Having fitted a Mason Alarm (superb piece of magic) I can just switch the fans on if the gauge creeps up (especialy when towing). Once again thank you to all members who have posted such a morass of useful information. Having just forked out £1400 for a recon gearbox, (Dunnings of Weymouth - great job)the raditator fan switch, the scavenge fan switch, and the Mason Alarm alll give me the confidence to carry on towing. Tanks to all , Peter

[mikeonb4c]

Thanks to the great deal of information posted by members (I realy am most grateful) I have fitted an over-ride switch by cutting one of the wires from the sensor in the block and feeding it to an on/of switch. The part I can't get my head around is "leave it in the "on" position when switching of the engine". By doing this the fans keep running even when the engines cold. "I am extreamly confused" of Dorset. Its not a problem as I just switch 'em off !!! Having fitted a Mason Alarm (superb piece of magic) I can just switch the fans on if the gauge creeps up (especialy when towing). Once again thank you to all members who have posted such a morass of useful information. Having just forked out £1400 for a recon gearbox, (Dunnings of Weymouth - great job)the raditator fan switch, the scavenge fan switch, and the Mason Alarm alll give me the confidence to carry on towing. Tanks to all , Peter

Gosh - 1st person to do that I think (though I could be wrong)! Can't get my head around your circuitry but presume it works OK

I fitted an over-ride to my scavenger fan but did that by providing a new switcheable feed via an on/off switch. It will even run with engine off (not that you'd forget to switch it off as its quite audible).

I'd be very interested to hear how effective switching rad fans on is at getting the temp needle to drop back from a high position esp in different situations e.g. when on the nove with engine working hard (where natural airflow is effective), or when stationary in traffic (where natural airflow isn't).

Anyway, well done

[dandywarhol]

Its because the fans are designed to cut in even when the engine is off and the keys removed. It's to allow for heat soak in the engine occurring when there's no airflow to cool it - especially when you've come off a motorway etc.

[Bongo Boozer]

Peter,
Can I ask why you needed a recon gearbox. Only I have just had mine done after giving up (sep post) and Dunnings have done mine.
It's just I did a search on the forum when mine gave up and to my knowledge I think that we are the only 2 people on here to have had a problem with a gearbox which has lead to a complete re-build.
I know its off subject but what lead to the new gearbox.

Cheers
Steve

[jaylee]

Gosh - 1st person to do that I think (though I could be wrong)! Can't get my head around your circuitry but presume it works OK

I fitted an over-ride to my scavenger fan but did that by providing a new switcheable feed via an on/off switch. It will even run with engine off (not that you'd forget to switch it off as its quite audible).

I'd be very interested to hear how effective switching rad fans on is at getting the temp needle to drop back from a high position esp in different situations e.g. when on the nove with engine working hard (where natural airflow is effective), or when stationary in traffic (where natural airflow isn't).

Anyway, well done

Its because the fans are designed to cut in even when the engine is off and the keys removed. It's to allow for heat soak in the engine occurring when there's no airflow to cool it - especially when you've come off a motorway etc.

We talking bout the angled fan in front of the engine??

You now what..? I've never seen that fan come on.. Been across Europe in blistering weather. It's never come on...
My old alarm system required a wire was fitted to a scavenger fan earth, because the system worked by sensing a voltage drop when alarmed... I never needed to attach it!!
I've since upgraded the alarm, works on a different method.

Apart from when i had a top hose go October last year (mason alarm fitted) i've never over heated.. Runs fine..!

Least i think it does.. Never really let me down in 2.5 years!

[missfixit70]

I think mine came on once when we'd been caning it up that mountain in Italy to the site we met you guys at, roasting hot day (before the storm), switched the engine off too soon & I'm pretty sure it kicked in for a few minutes, but other than that, never noticed it come on before.

[Peter2414]

Hello Steve, in reply to your question as to why the gearbox failed. I work in an evironment where we trial and develop vehicles and equipment so I am surrounded by expert engineers ( I'm more of the plugs, points, and condenser kind of engineer). I also took advice from Dunnings of Weymouth who are the recognized experts. The answer is not simple (it never is). Basically the gearbox overheated, and hung on to second gear.This was because:

1. It was a very hot day and we had towed our 1200kg caravan at about 60mph for three hours on the M5.
2. The gearbox oil may have been low (I hadn't checked it for a while and mineral oil does get "used").
3. Mazda's wisdom of fitting the gearbox oil cooler in the lower part of the engine radiator seems a little suspect (good heat exchanger between the two systems). Ours is a 97 model and I looked at a 95 model and the gearbox oil cooler is a seperate unit in front of the radiator. Begs the question why was the design changed, to save money maybe?.
4. Mechanical wear and tear ( 75k miles) Probably one of the four electricaly operated solenoids in the gearbox failed due to wear or the high temperature.
5. One, or both of the cooling fans thermal sensors may be suspect.

In view of all of the above I fitted the Mason Alarm and manual over-ride switches for both the scavenge fan and the radiator fans, together with a new larger oil cooler mounted in front of the radiator (by Dunnings-reduces the gearbox oil temp by 20c). I now feal confident that I can manage both cooling systems, especially as the engine cooling system coped very well for two hours at 4500 revs !! Hope this all makes sense !!! Peter

[mikeonb4c]

In view of all of the above I fitted the Mason Alarm and manual over-ride switches for both the scavenge fan and the radiator fans, together with a new larger oil cooler mounted in front of the radiator (by Dunnings-reduces the gearbox oil temp by 20c). I now feal confident that I can manage both cooling systems, especially as the engine cooling system coped very well for two hours at 4500 revs !! Hope this all makes sense !!! Peter

Slurp slobber - it would be great if you felt up to doing a little article/factsheet on what you've done, how to do it, and when and why it might be useful mods for a Bongo owner to make. Really useful sounding mods it seems to me. Out of interest, have you a temp. gauge so you are able to observe the effect of switching on (1) the rad fan over-ride and (2) the scavenger fan over-ride?

Great work

[Peter2414]

Hi Mike,
Thanks for the kind comments. I obtained all the information I needed from this very forum and am most grateful.
No I don't have an additional water temperature gauge, I rely on the Mason Alarm to indicate when I should switch the fans on, and together with the original two senors (hopefully working OK) I feal fairly confident.
I retire next year and shall change the radiator, thermostat, cam belt and tensioner, and the ATF, so hopefully Bertie will out live me !!! It does everything we need superbly well and mechanicaly is a fairly simple and robust beast (even with its quirks!!). The electronics however are way beyond my skill level !!!!

Regards,
Peter

[mikeonb4c]

Hi Mike,
Thanks for the kind comments. I obtained all the information I needed from this very forum and am most grateful.
No I don't have an additional water temperature gauge, I rely on the Mason Alarm to indicate when I should switch the fans on, and together with the original two senors (hopefully working OK) I feal fairly confident.
I retire next year and shall change the radiator, thermostat, cam belt and tensioner, and the ATF, so hopefully Bertie will out live me !!! It does everything we need superbly well and mechanicaly is a fairly simple and robust beast (even with its quirks!!). The electronics however are way beyond my skill level !!!!

Regards,
Peter

Sounds good to me Peter

Wool eh? Many's the time I've wended my way over the Isle of Purbeck through the Army Ranges, rejoining the road to Weymouth at Wool and stopping off to fly my model gliders at Ringstead Bay.

Happy Days