rad fan re-wiring assistance

[dark_knight]

i've heard & read several (other) posts about people re-wiring their rad fans to engage on-demand at the flick of a switch but haven't quite found one that has had done what i'm looking for so please hear me out: is it possible to retain the rad fan relay feature, meaning the thermo switch/relay will still activate the fan when hot but still allow me to still override this and engage the fan manually..? i'd like this routed through an IGN-activated power feed so that i can't accidentally leave the fan engaged and drain my battery after the engine is off.

i ask because i've noticed that at times even though the engine is hot at about 94+ deg C, the rad fan only engages for about 5 to 10 seconds then goes back off for an extended period of time before kicking in again. in my understanding, i thought the thermo switch should remain open the whole time until the coolant temp drops below the threshold, which i suspect is 94C..?
can anyone shed some more light on this..?

 

[GT-TD04]

Perhaps your thermostat is getting stuck closed,might be worth replacing if it is indeed this problem. When its at normal temperature,does it drop when you drive it or when you put on the heating?

As for the wiring,
My understanding of it is the sensor sends a 12v current down to the fan when certain temps are reached,and then stops sending it when it temperatures go back down.

So if you wired a 12v+ (lets call this B) wire into the fan loom after the sensor (so just before the connector on the fan) to the + wire one the fan (there is only two i think,so earth and 12v+) you could send power to the fan independently of the temp switch.

Once you had your wire (B) wired into the loom you would then need to get a current going through it activated by a switch.


The way I would do it is
T your new wire (B) into a 12V+IGN at the radio or ignition.
Run this wire through the firewall and T it (B) into the power wire on the fan about 8inches back from the fan connector.
Then T in a switch onto B (inside the cabin) so as to stop or allow current,thus giving you control over the fan.


Now I'm not great at wiring so wait for someone else who knows a bit more who can either confirm the above or give you the correct answer.

I'd try it myself but I dont have a starlet at the minute. To test it if no one else replies you can just try running a temporary wire from the back of the radio to the fan connector wire,if it powers up it'll work. A face tester would help alot

 

[dark_knight]

thanks GT-TD04. had a bad day as mine was broken into and they made off with my stereo face-plate. a little vexxed but will still review your suggestion and test.. thanks mate. much appreciated..

 

[dac69er]

the fan will be controlled by a relay, just control that and your sorted.

from what i can assume the control is failsafe. the sensor grounds out one side of the coil on the relay. when the temp gets too hight the circuit it broken, the relay switches and the fan comes on.

i would say its probably best to just wire into the pressure switch on the aircon. make and break that circuit and the fan will come on and off

can anyone confirm this? im just assuming this due to the fact you remove the plug off the sensor and the fan comes on

 

[Texx]

Wire the switch side of a normally closed relay between the fan switch in the stat housing and the fan switch connector, then ground one of the coil terminals and connect the other coil terminal to a switch inside the car that supplies an IGN only +12v.

This will give you the ability to switch the rad fan on via a switch on the dash and also retain the stock thermo switch function when the dash switch is in the OFF position. Feeding the normally closed relay with an IGN switched +12v will prevent you accidently leaving the rad fan running once you've left the car parked up.

 

[dark_knight]

override switch

dac69er, mine is the glanza platform so i'm unaffected by removing the air-con and having the rad fan constantly on.
i think what Texx has suggested sounds like a good plan -- i'm guessing i'll need a relay for that..? was hoping all i'd have to get was the switch.. but that's me being lazy..
will draw up a schematic and share here to see if i'm on the right track..

 

[weeJohn]

The rad fan switch on the thermo housing pulls a relay in when it switches to earth, all you need to do is connect a wire from the rad switch wire (at the plug on the thermo housing) and run it through the bulkhead to the dash. Then fit your fan on/auto switch on the dash, connect that wire to it and the other side of the switch to earth. That will make it work a Texx describes above and as the switch is only operating the fan relay there will be very little current running through it.

Back to original issue, where are you measuring the water temps for the Defi gauges? It might be possible the fan is cooling the coolant more than you can see due to the sensor location.

 

[dark_knight]

coolant temp pick-up location

i'm picking up my coolant temp readings adjacent to the thermo housing right next to where the OEM gauge sender is. i guess this is the best place for this..?

 

[weeJohn]

Where I take it from as well.

 

[dark_knight]

will this work?

not to disregard what you suggested Texx but just wondering if this will work..? even though i know it may not have any ignition-only mode. not too sure how to wire in the NC relay you mentioned. think you can draw up something similar for me to follow..?

 

[weeJohn]

That will work as long as the middle wire (from the relay) on the switch is the common. Only thing about doing that way is you will have to cut and extend the switch and relay wires into the cabin from the engine bay.

 

[dark_knight]

schematics

now, if only Texx would share a schematic of his explanation above..

 

[weeJohn]

now, if only Texx would share a schematic of his explanation above..

Its pretty much the same as you have, but your switch is replaced with a relay and there is another switch. To be honest, there is such a low load off the relay that runs the fan, the circuit you drew would still work 100%.

 

[dark_knight]

i know weeJohn, but i'm a little lost at how the actual relay wiring will come into play with the (ignition) line that's energized only by the key..

 

[Stu-]

The way I would do it is
T your new wire (B) into a 12V+IGN at the radio or ignition.
Run this wire through the firewall and T it (B) into the power wire on the fan about 8inches back from the fan connector.
Then T in a switch onto B (inside the cabin) so as to stop or allow current,thus giving you control over the fan.

Dont mean to pick but thats probably not the wisest way of doing it. The fan draws quite a lot of current so you'll be blowing fuses if you wire from the radio circuit.
As other posters have said, the stock relay requires an absense of earth to make the fan run (aka unplug the sensor and the fan relay triggers turning the fan on). You can splice the line into the cabin on a defeat switch so you essentially interupt the earth from the sensor to the relay which will cause the fan to run. It'll run just like stock in the mean time.

 

[dark_knight]

then tell me this Stu-, what triggers the rad fan relay 1 to power the fan..? is it not the thermo switch earthing to the engine block..?

 

[Stu-]

The fan relay is triggered by an absence of earth on the sensor side. For example if you un-plug the sensor plug from the thermostat then the earth to the relay is cut causing the fan relay to engage which supplies power to the fan. The sensor itself is normally closed and opens when it gets to temp. So when the fan is not running (engine cold) there is earth from the engine to the relay keeping it open.

My comment above was about running a new power feed direct to the fan (not relay) from the radio or ignition circuit. The fan draws quite a bit of current so its better to wire the overide switch into the trigger side not the power side.

 

[dark_knight]

ignition override

good thinking. so then, if i simply add an on/off switch in between the thermo switch and the rad fan relay, question is, on the override position, with the ignition off, will the relay still be energized (or not) to keep the fan running..? looking at a situation where my override switch is in the 'on' position -- meaning the fan is running, but would like it to cut out when the ignition is 'off' as well. this is something i would like to test..

 

[Stu-]

No the relay wont kick in with the ignition off as the main circuit open relay supplies power to the fan relay. You could change the supply to the fan relay so it direct to the battery as a work around but I'd be putting a fuse in there somewhere as you wouldn't be Protected by the main fuses.

Why do you want to run the fan after the ignition is off? Turbo timer not do the trick? the water isn't circulating with the engine off anyway so your only cooling the radiator and not the engine.

 

[dark_knight]

ignition override

no no no Stu-.. you got it bad. i DON'T want the fan to run with the ignition off. i would not like an instance where, say i've gone on a spirited drive and had the fan switch on the override position only to park and leave it still running even with the ignition off. it would kill my battery in a matter of minutes -- hence the reason i need a solution that will allow me to override the fan relay to keep the fan running when i want it to (with the engine still running) but with the ignition fail-safe to keep the fan off when the key is out of the barrel. will go give this a shot and see. will be very glad if it works..
thanks for sharing. repped!