3 way fan switching

[Apache]

O...K...

In your diagram, when in the fan off position, there is a positive feed through off bulb (which is what you want), but, according to the diagram, there would be current flow through the override bulb to earth. Assuming the bulbs are of equal wattage, each bulb is only half as bright as it should be as there is only 6v across each. The relay coil appears to be in parallel with the override bulb. Whether the override bulb does or doesn't illuminate in this case would depend on the resistance of the relay coil (and automotive ones tend to be fairly low resistance compared to say, communications relays) as a lower resistance coil would tend to consume the lions share of the current.

Still, what you have works, which was the point!

[Vagrant No2]

O...K...

In your diagram, when in the fan off position, there is a positive feed through off bulb (which is what you want), but, according to the diagram, there would be current flow through the override bulb to earth. Assuming the bulbs are of equal wattage, each bulb is only half as bright as it should be as there is only 6v across each. The relay coil appears to be in parallel with the override bulb. Whether the override bulb does or doesn't illuminate in this case would depend on the resistance of the relay coil (and automotive ones tend to be fairly low resistance compared to say, communications relays) as a lower resistance coil would tend to consume the lions share of the current.

Still, what you have works, which was the point!

In the off position the overide bulb and relay have no positive feed but the off bulb gets a positive feed and uses the overide bulb and the relay as earths instead of positives. As they are in paralell there is insufficient voltage to illuminate the overide bulb and the relay has the lower resistance , as you pointed out , and acts just as an earth as the relay also has insufficient voltage to work as a relay . I did try the circuit without the overide bulb and it did trip the relay in sometimes .Thats why I think the overide bulb takes the surge out the system and stops the relay coming in .
I am now getting my headache back !
I am just an old spanner monkey who dabbles in a bit of auto electrics .

[Apache]

In the off position the overide bulb and relay have no positive feed but the off bulb gets a positive feed and uses the overide bulb and the relay as earths instead of positives. As they are in paralell there is insufficient voltage to illuminate the overide bulb and the relay has the lower resistance , as you pointed out , and acts just as an earth as the relay also has insufficient voltage to work as a relay . I did try the circuit without the overide bulb and it did trip the relay in sometimes .Thats why I think the overide bulb takes the surge out the system and stops the relay coming in .
I am now getting my headache back !
I am just an old spanner monkey who dabbles in a bit of auto electrics .

Not the most elegant way of doing it, but then spannering hurts MY head. I was sitting here at midnight last night with a few bottles of Theakstons under the belt thinking about your problem and came up with a solution that utilises 4000 series logic and solid state switching via mosfets. Yours is probably cheaper, but mine's more 'star trek'

[Vagrant No2]

Not the most elegant way of doing it

Hey , I aint never ever been called elegant or ever been known to do anything that could been called elegant
I just thought the way I did was the best ? I did ask right at the begining of this , now long , thread if anyone had an easy way to do this that was not to techy .

[MattF]

By the looks of the diagram, a three position rotary switch
would have been easiest. Popping a diode in between the
override lamp and the far side of the thermo will prevent the
override lamp coming on in normal mode.

With regards to the relay chatter, dropping the far side of the
off lamp straight to earth should sort that, instead of having it
connected to the override position. (I'm beginning to lose
track of it now).

[Vagrant No2]

By the looks of the diagram, a three position rotary switch
would have been easiest. Popping a diode in between the
override lamp and the far side of the thermo will prevent the
override lamp coming on in normal mode.

With regards to the relay chatter, dropping the far side of the
off lamp straight to earth should sort that, instead of having it
connected to the override position. (I'm beginning to lose
track of it now).

I did try an old Lotus wiper switch which was rotary but not enough room behind the panel for it , plus I did not like the wiper picture on the knob .
When you start talking diodes etc is when I get real lost ! Hence the KISS theory .
I had not tried the off wire to earth b4 as I did not have the feed I wanted at that time .

[MattF]

Say, for example, you used a 1N4007 diode, the red wire in
your diagram between the override bulb and the far side of
the thermo would need to be snipped, and the diode inserted
between the two ends of the now snipped red wire with the
silver band on the 1N4007 facing towards the thermo.

If you like, I can have a delve through my bits and see if I might
have any rotary switches which might do the job.

[Apache]

There's always an easier way as I know to my eternal cost.

I wont tell you about the lengths I went to in trying to compress the tensioner following a timing belt change. Suffice to say the chaps in the local motor factors still remind me about it 6 months on!

Give me wiggly amps any day!

[Vagrant No2]

Thanks Gamedawn

I fitted a 2nd fan today as the fan was on alot and did not switch off after a run on the motorway . So I now got 2 2nd gen fans fitted and they switch on/off nice and quick now . Thanks to Roger for donating the 2nd fan .
Tony had fitted 2 fans when he did his , but Jon had given me one fan , so I fitted just the one .

[Gamedawn]

I fitted a 2nd fan today as the fan was on alot and did not switch off after a run on the motorway . So I now got 2 2nd gen fans fitted and they switch on/off nice and quick now . Thanks to Roger for donating the 2nd fan .
Tony had fitted 2 fans when he did his , but Jon had given me one fan , so I fitted just the one .

You managed to find some bolts then

[Vagrant No2]

You managed to find some bolts then

Yep , I managed to find 2 the same as the original ,somehow and the nuts aswell. They were laying on the garage floor !. Must have been from the A/C I sttripped out .I needed 1 more and used a new one from the draw , not the same , but similar.

[Gamedawn]

Do you give lessons? I can never find a bolt the right length or size, or if I can I can't find a nut to fit. Ty-raps are a wonderful thing