johnwill Posted June 3, 2022 Report Share Posted June 3, 2022 (edited) 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 June 3, 2022 by johnwill Typo Quote Link to post Share on other sites
ed_h Posted June 3, 2022 Report Share Posted June 3, 2022 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 Quote Link to post Share on other sites
Andy Moltu Posted June 4, 2022 Report Share Posted June 4, 2022 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. Quote Link to post Share on other sites
RogerH Posted June 4, 2022 Report Share Posted June 4, 2022 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 Quote Link to post Share on other sites
Andy Moltu Posted June 4, 2022 Report Share Posted June 4, 2022 I assume it’s a PI car so no carbs. My concern was more about the timer relay - seen a couple decide to stay on way too long. Quote Link to post Share on other sites
RogerH Posted June 4, 2022 Report Share Posted June 4, 2022 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 Quote Link to post Share on other sites
johnwill Posted June 4, 2022 Author Report Share Posted June 4, 2022 My thoughts are to keep it the same as my 4A, fan switches off with ignition. yes, PI system. Quote Link to post Share on other sites
Andy Moltu Posted June 4, 2022 Report Share Posted June 4, 2022 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. Quote Link to post Share on other sites
Tim D. Posted June 4, 2022 Report Share Posted June 4, 2022 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 Quote Link to post Share on other sites
Andy Moltu Posted June 4, 2022 Report Share Posted June 4, 2022 It may do no harm, but does it do any good? Quote Link to post Share on other sites
North London Mike Posted June 4, 2022 Report Share Posted June 4, 2022 +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 Quote Link to post Share on other sites
johnwill Posted June 5, 2022 Author Report Share Posted June 5, 2022 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? Quote Link to post Share on other sites
RogerH Posted June 5, 2022 Report Share Posted June 5, 2022 You could add a 10 minute timer to the override switch to shut down automatically after turning the ignition off Roger Quote Link to post Share on other sites
North London Mike Posted June 5, 2022 Report Share Posted June 5, 2022 9 hours ago, johnwill said: What would the wiring diagram look like for that? John I wish I knew 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 Quote Link to post Share on other sites
ed_h Posted June 5, 2022 Report Share Posted June 5, 2022 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 Quote Link to post Share on other sites
johnwill Posted June 5, 2022 Author Report Share Posted June 5, 2022 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 Quote Link to post Share on other sites
ed_h Posted June 5, 2022 Report Share Posted June 5, 2022 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 Quote Link to post Share on other sites
johnwill Posted June 6, 2022 Author Report Share Posted June 6, 2022 (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…) thanks john Edited June 6, 2022 by johnwill Quote Link to post Share on other sites
Lebro Posted June 6, 2022 Report Share Posted June 6, 2022 Looks about right Bob Quote Link to post Share on other sites
ed_h Posted June 6, 2022 Report Share Posted June 6, 2022 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 Quote Link to post Share on other sites
johnwill Posted June 6, 2022 Author Report Share Posted June 6, 2022 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? Quote Link to post Share on other sites
ed_h Posted June 6, 2022 Report Share Posted June 6, 2022 The fan needs an earth, but the switch doesn't. It was only needed for the internal light. Quote Link to post Share on other sites
johnwill Posted June 6, 2022 Author Report Share Posted June 6, 2022 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 Quote Link to post Share on other sites
ed_h Posted June 6, 2022 Report Share Posted June 6, 2022 Can you post a diagram of how you have it wired? Ed Quote Link to post Share on other sites
johnwill Posted June 6, 2022 Author Report Share Posted June 6, 2022 (edited) 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 June 6, 2022 by johnwill Quote Link to post Share on other sites
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