Eastside Cruisers

Hey guys,

Keen to hear some thoughts on this one...

Ever since I can remember, I've had my thermo fans wired to a manual switch. Works like a dream - unless you forget to turn them on! My manual toggle switch was switching the relay Earth (I prefer switching Earth circuits rather than active 12V circuits after a bad experience with a fried switch).

So anyway, recently I thought it was about time that I changed the wiring in an attempt to make the fans turn on and off automatically with the ignition. So this is what I've now done (apologies for the crap explanation and lack of wiring diagram!!):

TWIN RELAYS:
* Earth - still connected to my toggle switch which connects to earth inside the cabin.
* Constant 12V Input - connected directly to main Alternator 12V pole.
* Switch Wire - connected to "Accessories" fuse on the main fuse-box.
* Output - connected to thermos obviously.

Ok, so my hope was that I could now leave the toggle switch permanently on, and the fans should turn on and off with the ignition. And it works perfectly - turn ignition on, fans come on. Turn ignition off, fans turn off.

If I now start the engine, the fans stay on - still looking good. However, turn the ignition off, and guess what - the engine keeps running!! I have to flick the toggle switch off (breaking the earth) in order to stop the engine. Which defeats the whole purpose of this exercise.

Is this some kind of back feed from the alternator 12V? Would a diode fix this? Are diodes reliable?

Any comments?

PS. I assume I haven't mixed up the Constant and Switch Inputs on the relay - will have to check this. But either way, the problem is still there.

I'm thinking you only need the fans to operate whilst the car is running.ie, you don't want them to stay on for x amount of time after the motor turns off. If so...
You wouldn't need the 12v constant wire, you could try connecting this to the accessories wire ( include a fuse if possible- just make sure you use the right amp fuses. then im thinking thermos should turn on / off with the motor if switch was left on.

If you're absolutely stuck, maybe try n call fletch at maroondah auto elec, club sponsor, n he may be able to help over the phone.

Lettuce know how you go.

sounds like a feed back through the ignition wire. very common especially if you are using falcon fans. and yes a diode will fix it.

Davis Craig make a kit that worked perfectly on Mitch's tonna they where wired of ingnition and it was crap but when we had the motor out we fitted the kit it had a sensor that goes In between the rad fins and a little dial to adjust when you want them to cut in and out kit was $80 odd bucks and made a huge sufferance to how the tonna regulated its temp around Winton didn't give any signs of running warm where before it would have been sh*t

Cheers guys.

The plan has always been to eventually fit a proper switch to automate the fans, I just need to get off my ass and do it.

Hey Iso, any more details on the Magna switch? What do they look like and where do they fit - eg a screw-in fitting or something else?

Also - so Leigh that Davies Craig one works purely off air temp in the radiator fins?

Yeah I was a bit suss on it at first but it worked just like a factory setup

here is the kit we fitted
http://www.daviescraig.com.au/Controlle ... tails.aspx