Cooling Fan Switch
Discussion
Needless to say I'll be overriding it with a switch 
Easy-ish to get at if you remove the nearside headlamp pod. Actually, you might be able to get at it by removing the headlamp unit and reaching in thru the hole...
Dont really go wrong though, so it you have a problem, this probably isnt it. Probably...
Easy way of wiring an override switch is to find the relay that powers the fan up on the relay board. I did this (cos the relays are all over the fricking place on the board and bear NO resemblance to any wiring diagram ive ever seen...) by locating the fuse (fuseboard in the bottom of the glovebox DOES match the sticker: weird..........), and tracing the wires.
The otter switch powers up the fan by earthing the relay when the otter switch contacts close. So, if you wire up a parallel earth path, and put a switch in it, you will be able to override the otter switch.
In laymans terms, I tapped into the wire that goes from the relay to the otter, put a rocker switch on it, and wired the other end of the rocker switch to earth.
Override switch on mine is nicely sunk into the top left hand side of the steering column shroud (Rover SD1 column).
Works a treat. Switch doesnt have to be too manly, as IIRC the control path of the relay only draws about 500mA anyway.
HTH.
Ed.
Dont really go wrong though, so it you have a problem, this probably isnt it. Probably...
Easy way of wiring an override switch is to find the relay that powers the fan up on the relay board. I did this (cos the relays are all over the fricking place on the board and bear NO resemblance to any wiring diagram ive ever seen...) by locating the fuse (fuseboard in the bottom of the glovebox DOES match the sticker: weird..........), and tracing the wires.
The otter switch powers up the fan by earthing the relay when the otter switch contacts close. So, if you wire up a parallel earth path, and put a switch in it, you will be able to override the otter switch.
In laymans terms, I tapped into the wire that goes from the relay to the otter, put a rocker switch on it, and wired the other end of the rocker switch to earth.
Override switch on mine is nicely sunk into the top left hand side of the steering column shroud (Rover SD1 column).
Works a treat. Switch doesnt have to be too manly, as IIRC the control path of the relay only draws about 500mA anyway.
HTH.
Ed.
Edited by ed_crouch on Saturday 9th June 22:49
The water-temperature of my 350i sometimes grow up to 120 degrees, especially in traffic jam after quick highway-ride or on the way up to a very high mountain, when it´s not possible to speed enough. Because of that I changed the old and only Kenlowe-Fan to two Spal-high-performance-Fans. But the switch turns the fans on only at nearly 100 degrees. I think, it´s a little bit to late.
In my opinion, rather than messing around with otter switches that are a pain to get to, I would fit an adjustable temperature switch. If you wire in parallel or in place of the otter switch it will cause the cooling fan relay to operate just the same.
If you can then get a temperature meter with a touch probe you can set the cut in temp very accurately. I have always used the capillary type and this can be snuck in under any hose clip as long as you use a thin piece of rubber under it so it doesn't get pinched onto a lip or flange. I believe you can get strap on types as well and you should be able to get for 20-25 quid so if you take into account 30 mins labour to replace an otter switch then pays for itself in the long run. When fitting if you run another pair of cables in parallel to a switch on the dash you also have an overide switch.
If you can then get a temperature meter with a touch probe you can set the cut in temp very accurately. I have always used the capillary type and this can be snuck in under any hose clip as long as you use a thin piece of rubber under it so it doesn't get pinched onto a lip or flange. I believe you can get strap on types as well and you should be able to get for 20-25 quid so if you take into account 30 mins labour to replace an otter switch then pays for itself in the long run. When fitting if you run another pair of cables in parallel to a switch on the dash you also have an overide switch.
I agree with correspondents who say "fit an override switch". I only have an "override" switch (no otter switch, see?). If you're disciplined (and doing a regular eye-sweep across the instrument panel) it's one less worry. For example, I switch it on as I'm leaving a motorway after a fast run to provide additional, early cooling as I meet traffic. I put a warning LED in circuit and I can reasonably estimate my speed around the NSL by how brightly it glows when the fan is being turned solely by the inrush of air 
- Streaky
- StreakyMine has been removed and the hole sealed up. fed up with the leaks etc. Fitted an in line just south of the thermostat housing. Its a tube with a sensor the dry side.
Might wire it up one day and see if it works. Being a naughty boy I rely on the override switch. Might wire in an LED one day...... I rely on the drop on the voltmeter, its substantial..... I need a roundtoit.
Might wire it up one day and see if it works. Being a naughty boy I rely on the override switch. Might wire in an LED one day...... I rely on the drop on the voltmeter, its substantial..... I need a roundtoit.
Like Streaky, my 350i has only got a manual switch - haven't had chance to look and see if the sensor is in place or even wired... But I generally find that all the time you are moving (even at 15-20mph) there's no need for the fans and I just flick them on when I stop and off when I start moving
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