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Fitted an electric fan to my “new” TR6, and now looking to wire it up

where do you wire to normally on a 6 for the unswitched positive? (Switched to fuse box as per my 4A, unswitched to horn relay)

straight to battery (with fuse)?

i had help for the 4A from Rob & others, and had good diagrams of how it should be, but want to make sure I get it right on the 6, so hoping for help again.

The sensor is in the middle hose from the base of the rad, and will have a manual switch (with light) also.

also, I’m running a new “bigger” wire from the fuse box to my new fuel pump (inc inertia switch). Anything to watch out for here, running 2 new wires to the fuse box?

thanks

john

Edited by johnwill
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I wired mine to unswitched power so that it can continue running with the ignition off.  At least some newer cars are wired that way.

Nothing wrong with connecting to switched power though, if that's how you want it.

Ed

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Do you need the fan to run after switching off draining the battery?

With the standard mechanical fan, airflow ceases on switching off. Yes a bit of heat soak will see the temp at the top of the engine rise and the top hose if that’s where your sensor is. If your sensor is at the bottom of the road that won’t occur. Is that heat soak likely to be damaging whist your engine is off? Probably not. 

As for modern cars, their fans running on after turning off may be for other reasons than simple coolant cooling. Oil cooling for the turbo or regeneration cycles for emission systems rather than dumping coolant heat, although that might be relevant with tight tolerances and fancy alloys when you might start within a minute or two.

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The rad fan running after switch off isn't a bad thing. 

Certainly on a 4A in the height of Summer there is every possibility of vapourisation at the carbs.

If the battery is in good order then the 5 minute power drain would be nothing.

Roger

 

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5 hours ago, RogerH said:

Timer relay !!

I thought it was the water temp/sensor that controlled the time.

But I agree if the sensor stuck on that would not be good.

 

Roger

It should be but if you have it controlled by an unswitched circuit there is a risk of it staying on and flattening the battery.

The switches have a reputation for failing - usually off but if on your battery is flat. Likewise the relay.

You can’t push start a PI with a flat battery as a decent voltage is needed for the fuel pump to deliver pressure enough to open the injectors. Less of an issue with carved TRs.

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Andy, good point but have had my fans wired to permanently live for some time with no failures. Had more flat batteries from lights being left on :-) . Running the fan after turnoff using thermocycling to move the coolant won't do any harm. 

tim

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+1 wired to non switched live, relay protected with an override switch

Never had a problem with the fan running on, flat battery etc in 15 yrs

However, ironically, I did manage to run the battery flat by leaving the override switch on (Doh!) Now, the override is ignition protected although the main fan remains live

Does it do any good, I feel so, never really happy leaving an already hot car to continue to cook when parked. I'd rather cool the rad whilst also pushing the hot air out of the engine bay. Used to suffer fuel evaporation with the SU's

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11 hours ago, North London Mike said:

+1 wired to non switched live, relay protected with an override switch

Never had a problem with the fan running on, flat battery etc in 15 yrs

However, ironically, I did manage to run the battery flat by leaving the override switch on (Doh!) Now, the override is ignition protected although the main fan remains live

Does it do any good, I feel so, never really happy leaving an already hot car to continue to cook when parked. I'd rather cool the rad whilst also pushing the hot air out of the engine bay. Used to suffer fuel evaporation with the SU's

What would the wiring diagram look like for that?

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9 hours ago, johnwill said:

What would the wiring diagram look like for that?

John

I wish I knew :lol: Grown over several years, thermo switched, then override added, then diverted via ignition. Rogers 10sec delay not needed as I'm still live on the main feed (thermo switched). Bit of a mess if I'm honest but it works. Someone cleverer than me (so, almost anybody) will be along in a while to do it properly :ph34r:

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10 hours ago, johnwill said:

What would the wiring diagram look like for that?

It would be nothing exotic if the fan is "high side switched".  This is where one fan wire is grounded, and the 12 volts is delivered through a switch.  The thermal switch can be connected to an "always live" point, while the override switch is connected  to a point that is only on with the ignition.  Both switches connect to the fan power wire.

If the fan is "low side switched", where it is connected to power (switched or unswitched) all the time, and it's ground comes from a thermal switch, it would be more complicated.

Ed

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1 hour ago, ed_h said:

It would be nothing exotic if the fan is "high side switched".  This is where one fan wire is grounded, and the 12 volts is delivered through a switch.  The thermal switch can be connected to an "always live" point, while the override switch is connected  to a point that is only on with the ignition.  Both switches connect to the fan power wire.

If the fan is "low side switched", where it is connected to power (switched or unswitched) all the time, and it's ground comes from a thermal switch, it would be more complicated.

Ed

Where would the always live point be on a TR6? I used the horn relay (already fused, on my 4A)

John

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1 hour ago, johnwill said:

Where would the always live point be on a TR6? I used the horn relay (already fused, on my 4A)

John

The fan is a significant load, so providing a dedicated fuse for it would be an excellent idea.  Simplest way would be an inline fuse holder.  Power could be sourced directly from the battery, or from any other point that is directly connected to the battery.  Direct connection to the battery terminal may be the safest, since adding fan load to an existing circuit may overload the wiring.

Ed

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Posted (edited)

Also, this is the wiring diagram for the switch if you want it to light up. I don’t, so any views on how to connect it? (I’m assuming just + and - to be used, but my assumptions can be dangerous…) :D

thanks

john

762602EE-95AC-432A-AE61-86740F1FA106.jpeg

Edited by johnwill
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If you don't want the internal light to operate, you can delete the connection to the "+" and/or the "-" terminals.  Keep the "C" and "N/O" connections.

Ed

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4 minutes ago, ed_h said:

If you don't want the internal light to operate, you can delete the connection to the "+" and/or the "-" terminals.  Keep the "C" and "N/O" connections.

Ed

Do I not need an earth?

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Thanks for the advice all. Still no luck after lots of fiddling.  Suspect the switch or relay…

Odd thing though (or is it?) if I connect a wire to 87 on the relay to earth, the fan spins. So power getting that far?

John

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Posted (edited)

image.thumb.png.90ba0fc142e7954b9cf7058fe22934a6.png 

Sorry about the size, not sure how to make smaller.

Sensor in water pipe not actually fitted yet. I have a different thread on that issue :-)

John

Edited by johnwill
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