Bypass/override switch for coolingfan.

[RazorbackNOR]

Does anyone recall something here about something like this? I seem to recall some talk about it and I'm interested in some more info on this, but searching the forum has not helped much. I think there was some talk about using a threepole illuminated switch so the light in it would switch on when the thermostat kicked in.

Any more info is greatly appriciated.

[suffolkpete]

You don't need a three pole switch, a normal single pole single throw will do unless you want to be able to turn the fan off when the thermostat switches it on, but I don't see why anyone would want to do that.  Wire the switch in parallel with the radiator switch and the connect the light to the switched feed on the switch.  You will then be able to turn the fan on manually and the light will illuminate whenaver the fan is on, whether manually or automatically.  I've got this arrangement on my car and it works fine.

[RazorbackNOR]

Hmm, I seem to recall someone talked about using an illuminated switch, and it was wired so that when switched on the light was off, and it only came on once the thermoswitch had switched on, and would have turned on the fan by it self, to indicated that things are working as it should.
Otherwise your suggestion is a wellworking one SuffolkPete. Did you mean putting in between 10 and 10A on the diagram? Is there somewhere closer to the dashboard these wires can be accessed?

[davidewanprice]

I think it may have been my thread but I was wanting to know how to light the switch. I have switch in place, located in between the radio and ignition. This takes a feed from the fan, and another through a fuse straight from the battery terminal. I made the switch light up by simply attaching the remaining free terminal on the switch to earth, I.E. a piece of metal.. It works... If anyone thinks this isnt correct id like to know..
I wouldn't want to wait for a light to come on, that sounds as unreliable as waiting for the thermostat to kick in, I just flick the switch whenever I hit traffic and looks like I may be stood for a while.. If its a long while I turn the fan on full on hot.. This seems to prevent any problems.... Touch some wood/MDF.

I must sort what's draining my battery tho, something is killing it within 5 days! It's a new battery too...

[suffolkpete]

Hmm, I seem to recall someone talked about using an illuminated switch, and it was wired so that when switched on the light was off, and it only came on once the thermoswitch had switched on, and would have turned on the fan by it self, to indicated that things are working as it should.
Otherwise your suggestion is a wellworking one SuffolkPete. Did you mean putting in between 10 and 10A on the diagram? Is there somewhere closer to the dashboard these wires can be accessed?

Yes, between 10 and 10A.  10 can be accessed from the ignition switch, or a number of other places behind the dashboard, it is coloured grey.  10A I think is only accessible at the front of the car.  Connect the lamp to 10A as well.

[Jon Weywadt]

-- I made the switch light up by simply attaching the remaining free terminal on the switch to earth, I.E. a piece of metal.. It works... If anyone thinks this isnt correct id like to know..
--
I must sort what's draining my battery tho, something is killing it within 5 days! It's a new battery too...

Perhaps the answer to your battery drain is in the top sentense 
Try drawing out the wireing you have made. Perhaps you will find that the light and fan ends in series, thus draining the battery. the lamp would not allow enough current flow to run the fan and the fan would not allow enough current to light the lamp. Not sure, but check it out.

[davidewanprice]

But surely if the switch is off then theres no circuit to drain from as neither light nor fan are active. I think it could more likely be the stereo or alarm related... Apart from this annoying fault my car has been running really well this year.

[RazorbackNOR]

I found your post on your switch davidewanprice
, but I don't thing it was that one I'm thinking about. I think this one spesificly stated about not coming on when manually switched, but gave light when on AND the thermostatic switch also switched, to indicate that it functioned correctly. I can have dreamed all this, but I'm so certain..... Looking at the diagram for the switch and for the fan/thermoswitch, I really can't see how this could be possible..... Two poles, going throu for opening/braking the curcuit, and one ground, since you need this for the light, connecting this to earth would as you showed, make it light normaly when switched on(as it should)

[RazorbackNOR]

Just figured it out! With a threepole illuminated switch connected between 10 and 10A AND also grounded, while turned off this switch will light up when the the thermoswitch engages and starts the fan. Light will go off when thermoswitch switches off again. Light will remain on if illuminated switch is switched on, regardless of thermoswitch.

This can be enhanced further, with a diode and a little extra wire to indicate only the the status of the thermoswitch only.

Will see if I can make a diagram of the layout tomorrow.

[RazorbackNOR]

So, here is then the different layouts.
Mind you I'm not an electrician or electrical engineer, so you'll have to bare with me on the drawings.....

1. Normal setup. This is how it normaly works(when it does)


2. Normal illuminated switch. This setup will give you the indication of when the thermo switch goes on and off with the light in the switch as long as the switch is off. Switching it on overrides the thermoswitch, engages the fan and switched the light in the switch on. Which means no indication of what the thermoswitch is doing as long as you override it. Also the easiest and probably the most used setup


3. Allways illuminated. This setup lets you have the switch allways illuminated no mater what. As long as the ignition is on, the light in the switch will glow. Can be ok if you allways want to know where your switch is.


4. Now this is the one! This is the setup I'm wanting. This makes the light in the switch indicate the status of the thermoswitch. Light off if not engaged, light on if engaged. Overriding with the switch has no effect on the light. It does require a little modification thou. you need to open the switch, break the connection between the lamp and the second leg on the switch and solder on a bit of wire to the now disconnected part of the lamp.. On the 10A wire, you also need to put on a diode, between the point where the newly added wire from the second leg of the switch comes in and the newly added extra wire, to rectify the current(so it doesn't flow back in the curcuit.

[krede]

My car is fitted with an override switch for the cooling fan... but if your cooling system is properly maintained, you will never need it.