Manual Fan Override Switch Questions

[johnhenry 20]

Afternoon all

 

Im wanting to install a Hi-Low fan override switch, I've read a lot of the topics about this, and found a diagram that works for me, as in it makes sense to me.

 

 

the only questions i have are;

 

1) what amp rating does the switch have to be, I have a 17Amp toggle switch sitting in the garage from another project, as the fan is 15Amp, should this be fine?

 

2) what wire thickness' in terms of amp rating should i use? same all over just to be safe?

 

3) where could i build in a fuse as a fail safe?

 

Cheers

John

[jackherer 543]

If you're using relays any switch will do as the load is going through the relay. The fuse for the fan should be 25A I think, if you take the power from the shunt box you can use the fused outlet already there for the fan loom or if you wire it straight to the battery put a fuse as close as possible to the battery terminal so as much wiring as possible is protected by it. The wire gauge is shown in your diagram, thin wire on the switch side of the relay and thicker stuff on the fan side.

[johnhenry 20]

Thanks jack, the whole AWG thing was confusing me, didn't know what it meant, but if i go off the mm2 thickness. it seems to be easy enough to understand.

 

so the 0.5mm2 relates to about 6± amps, and the 3.0mm2 wire is 27.5 Amps - which works for me! in fact i think i have some in the shed.

[jackherer 543]

AWG is American Wire Gauge so you can safely ignore that!

[johnhenry 20]

had a though, last question

 

The red wire - from the battery, shouldn't that be abit thicker? how can that get away with being so thin? I'm not great with electrical

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[jackherer 543]

The red wire is supplying the very low current to the switch which is just used to activate the relays. The high current positive supply is via the existing fan wiring. That means you only need a very small fuse too so ignore what I wrote earlier about a 25A.

[johnhenry 20]

thanks so much jack, everything is cleared up perfectly, will be ordering parts this morning and cracking on with an install guide hopefully

[johnhenry 20]

okay, lil update I've assembled the relays, flying sockets and wires. pretty happy with it so far!

Only question I've got so far is that - where is the toggle switch 'live' coming from? red wire on the diagram above. - can it come from something like the cigarette lighter as that will have a live feed?

Cheers john

 

EDIT - attached photo of progress, isn't great photo but at least shows I'm getting there!

Edited October 24, 2014 by johnhenry

[jackherer 543]

Any switched live will work but personally I would use the switched live feed going through the brown multiplug in the drivers footwell that supplies the engine with its switched live which is wire number 2.

[mrfirepro 127 1 Cars]

Will it not be possible just to wire a two way switch across fan test connector??

[welshpug 1,666]

not advisable, its just a test point, the wire gauge is far smaller than the fan wiring itself.

[johnhenry 20]

I used the fag lighter as a power for the toggle switch to test it, - it works!

I got myself really confused about the switched live off the multi plug described above - through my own dumbness rather than instructions

basically, The wiring has been out of my car completely, and there are 2 brown multiplugs I can see in the area.

One of them comes off the ignition barrel, the other is just in that area, which one is it?

Here are photos of both

 

IGNITION BARREL multiplug

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OTHER multi plug

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Cheers

John

[welshpug 1,666]

neither of those but in the background of your last picture you'll see the engine loom coming through a grommet, follow this wiring back and you'll find the two brown plugs as long as the car is post 87.

[johnhenry 20]

found it! found number 2 wire too, wired it up, it works perfectly!

the 25A fuse on the shunt box blew out on its maiden voyage, have replaced and tested with main beam and wipers on full tilt on the driveway, and it seems to work fine now, was an old looking fuse so I think it might have been a tired fuse!

 

Will produce a lil guide to install and forward to mods/jack/welshpug to see if it makes sense, and we can go from there

Thanks all! John

PS - I HAVE A TOGGLE SWITCH NOW

[Tom Fenton 1,548]

Not trying to pick fault, but I don't understand why so many folk feel the need to install manual/override switches for radiator fans. When the standard setup is working it's simple and effective.

[welshpug 1,666]

totally agree tom

[jackherer 543]

Me too but at least this way it is an override, it's the people that only run a manual fan that I really don't understand.

[johnhenry 20]

I totally get why people don't have an override

I have however had a real mare with fans before, so i wanted to have an override, Dead chuffed with this now