Toggle Switch

[Black Cat]

I'm will shortly be installing a Revotec thermostatically controlled fan controller which has a relay for my electric fan on my Triumph Spitfire 1500 and I was thinking of installing a fan override toggle switch.

Not being electrically minded what exactly is a toggle switch or can I use any type of switch or does it have to be a specific type of switch?

What I don’t want is a switch which sticks out, I’m looking for a small rocker type of switch which I can locate in a suitable position and possible with a light built in to indicate the fan is on.

Many thanks

[NonMember]

There are several aspects of a switch that can be specified, electrical, functional and mechanical. The term "toggle" is, unfortunately, used in more than one way.

Electrical:  The switch has both voltage and current ratings. You will often see these quoted as different for AC and DC, not because switches care at all but rather because certain types of load (inductive, including motors and relays) are more punishing on DC than AC. If you're using the switch to directly bypass the Revotec then it must be rated for more DC Amps than the motor draws.

Functional: Switches can be "momentary" - you need to keep holding it - or "latching". The latter is sometimes called "toggle", especially if it's a push-on-push-off type. You will need a latching switch.

Functional/electrical: In the case of momentary switches, they can be "normally on" or "normally off". For all switches, they can be "single throw" (just on or off) or "double throw" (three terminals, the switch throws the centre from one side to the other). They can also be "single pole" or "double pole" (or even multiple pole), meaning there are more than one isolated electrical switch all controlled from one physical knob. You probably only need single pole.

Mechanical: The operating knob can be of many shapes - a push button, a rocker, a sticky-out thing. That last is sometimes, confusingly, called a "toggle". It sounds like you want a rocker switch.

So, you're after a single pole, single throw, latching (non-momentary) rocker switch with a DC rating of at least 15V and 20A (typical electric fan motor).

[RogerH]

Hi BC,

 not sure how the Revo controller works but most of these would do what you want  Switches

You need to power the fan through a relay. The relay then takes the BIG amps and the switch takes the small amps.

As you do not know what these switches are - are you happy working on electrics on your car !!!??

 

Roger

[dougbgt6]

Toggle switch needs a round hole whereas toggle needs a rectangular hole.

From Roger's list:

Heavy Duty On / Off / On Toggle Switch 25 AMP Rated 12v / 24v 3 Way Positions | eBay

 

Rocker switch

On/Off Rectangle Rocker Switch + Cover Car Dashboard Dash Boat 12V | eBay

 

Doug

[johny]

The Revotec site is pretty good with fitting instructions for the items they sell.  This page shows how to wire in an overide switch (they do offer a rocker type) to operate the relay already incorporated in their controller so avoiding the need for another.    070075.pdf (revotec.com)

However you might want to use their 3 way switch (if you want a way to turn off the fan manually) as, to avoid possible overloading of existing wiring/ignition switch, the fan controller should be powered directly from the battery via a fuse mounted as close to the battery as possible.

[chrishawley]

Auto Electrical Spares have a wide range of rocker (and other) switches many of them in a style more aesthetically sympathetic to a classic than a 'modern generic'. Poss worth a look. Sounds like what you want is an suitably rated (as per post above) 'click, make or break' switch.

The 'best' way to wire in a electric fan is definitely a case of 'as many men, so many opinions'. For me the Revotec wiring diagram is both a blessing and a curse. The good aspect is that it allows the fan to run on after the ignition is turned off until cooling has occurred. But the bad aspect is that the switch would allow the fan to be left running constantly with ignition off and at 10 - 12amps battery drain would rapidly supervene. And possibly (not sure) the Revo wiring might not allow the illumination of an illuminated switch to illuminate.

[johny]

18 minutes ago, chrishawley said:

The 'best' way to wire in a electric fan is definitely a case of 'as many men, so many opinions'. For me the Revotec wiring diagram is both a blessing and a curse. The good aspect is that it allows the fan to run on after the ignition is turned off until cooling has occurred. But the bad aspect is that the switch would allow the fan to be left running constantly with ignition off and at 10 - 12amps battery drain would rapidly supervene.

Yes thats always a conundrum. My solution has been to wire the supply to the relay coil and sensor in the Revotec diagram through a mechanical temperature switch attached to the radiator. Its an added layer of complexity but means when the rad cools to 60º theres no risk of fan run on (unless its relay sticks of course🤪) or the electronics draw flattening the battery...

[NonMember]

39 minutes ago, johny said:

means when the rad cools to 60º theres no risk of fan run on

When I bought my Vitesse it had a Kenlowe adjustable thermostat controller with its probe stuck in the top hose, as per the instructions. One evening I'd driven to a mate's house in Ely (for band practice) which isn't far, so it was only moderately warm. Mid evening I popped out to grab something from the boot and noticed the fan still running and flattening the battery, despite the radiator being stone cold. The coolant level had dropped just enough that, when running it had got the probe hot, but when stopped there was nothing to cool the probe down.

[Black Cat]

Thank you gents for your constructive comments.

This is what I’m proposing to do.

Firstly aquire a single pole rocker unlit switch with a DC rating of 20A. (An illuminated switch will not tell me the fan is running, only that it’s getting          power.)

Secondly follow the Revotec wiring diagram below with the added options: -

Install a 20amp fuse close to the battery 12 volt supply

Connect a new 18-20g wire to the live feed between the relay and the fan live connection to a warning LED bulb with a built in resistor on the dash and            then ground the bulb

Is it necessary to add an additional 1-2A fuse to the live feed to the bulb to protect the line feeding the light as close as possible to where I make the splice into the wire going to the fan?

Will this work or should I get an electrician to wire it up?

 

[NonMember]

Ah, jolly good.

So, first, if you're following that diagram then, as RogerH pointed out, the switch isn't carrying motor current and doesn't need a 20A rating. That may make it easier to find (or cheaper!)

On the other hand, that wiring diagram assumes a "double throw" (SPDT) "centre off" switch to select between automatic, off and permanently on. If you only want to be able to override to on, then you don't need centre-off. Alternatively, an SPST from the "blue" controller-to-relay wire down to earth, leaving the connection from controller to relay intact, is probably sufficient. However, check whether that's approved - I can't see any reason they wouldn't use and "open drain" output but you never know...

Adding the 20A fuse is a good idea - though be prepared to consider a 30A one if it's a big fan. The LED bulb is also a good idea and a low rated fuse at the fan end of that wire would protect against some possible wiring faults without taking the fan out of action. Technically, even then, the bulb doesn't tell you if the fan is running, only whether it's powered, but since the difference relates to seized motor bearings and the like, you may not be so fussed about that.

[PeteH]

Probably the only way to tell if the fan is actually running would be to monitor the Current draw?. The how? might be problematical. A "shunt" maybe?.

Pete

[johny]

Just a thought, the LED indicator in the propsed layout may well light up when the fan isnt powered because the fan can spin by the airflow when driving at speed and generate a voltage. Modern vehicles have this problem and use diodes to stop this reverse flow of current... 

[NonMember]

1 hour ago, johny said:

Modern vehicles have this problem and use diodes to stop this reverse flow of current

Unlikely. They may well have diodes but the reason won't be that.

When I worked at Rover's in-house ECU department, the team working on the Rover 218 asked us to turn the cooling fan on above a certain road speed. We told them we didn't have a road speed sensor as it was too expensive. They said we might need one. We said it would be on their cost centre. You get the drift. Anyway, we asked why they wanted the new feature, and they said the fan spun up so fast because of air flow at the vehicle's maximum speed that it exceeded the manufacturer's safe limit for the bearings. They wanted it turned on to slow it down (because at that speed it was generating more than the battery voltage, so turning it on would treat it as a generator). We told them to put a diode across the relay - when the fan spun that fast the diode would conduct to make use of the current flow to protect the bearings.

The other reason for diodes, if the fan is driven directly by a FET, is to quench the inductive flyback, which has nothing at all to do with the fan spinning.

[johny]

9 hours ago, NonMember said:

Unlikely. They may well have diodes but the reason won't be that.

When I worked at Rover's in-house ECU department, the team working on the Rover 218 asked us to turn the cooling fan on above a certain road speed. We told them we didn't have a road speed sensor as it was too expensive. They said we might need one. We said it would be on their cost centre. You get the drift. Anyway, we asked why they wanted the new feature, and they said the fan spun up so fast because of air flow at the vehicle's maximum speed that it exceeded the manufacturer's safe limit for the bearings. They wanted it turned on to slow it down (because at that speed it was generating more than the battery voltage, so turning it on would treat it as a generator). We told them to put a diode across the relay - when the fan spun that fast the diode would conduct to make use of the current flow to protect the bearings.

The other reason for diodes, if the fan is driven directly by a FET, is to quench the inductive flyback, which has nothing at all to do with the fan spinning.

I think it was on Wheeler Dealers or some such telly programme as they were fitting a double cooling fan set up to one of their vehicles and they showed that by spinning one fan by hand the other rotated driven by the generated power...

[dougbgt6]

13 hours ago, Black Cat said:

An illuminated switch will not tell me the fan is running, only that it’s getting          power.

The temperature gauge will tell you if the fan is working!   

The light reminds you to turn it off once the correct temperature is achieved. Running too cold for extended periods is not good for the engine.

Doug

[mpbarrett]

Slightly OT, but why do you need a separate temperature sensor when you already have one driving the temperature gauge?

Just monitor the voltage across the sensor, simple comparator (with adjustable threshold) and drive the relay to turn the fan on.

Am I missing something?

mike
 

[chrishawley]

BlackCat: I like your proposal (as above) for it's simplicity and doityourselfability.

SWG19 (≤1mm) is more than adequate for a LED. Fuse on the LED feed, as you suggest, is desirable in the event of a short.

I'd go DIY rather than spend ££s and then you're familiar with everything should later revisions be desired/needed.

 

 

 

[PeteH]

2 hours ago, mpbarrett said:

Slightly OT, but why do you need a separate temperature sensor when you already have one driving the temperature gauge?

Just monitor the voltage across the sensor, simple comparator (with adjustable threshold) and drive the relay to turn the fan on.

Am I missing something?

mike
 

I am not 100% sure, but most older temp gauges will be bimetallic strips and the current is what heats the strips, the voltage is generally stabilised at about 10V. you would need to measure current in that case?. 

Pete

[NonMember]

1 hour ago, PeteH said:

the voltage is generally stabilised at about 10V

No, that's the voltage at the top of the gauge. Mike proposed to measure at the bottom of the gauge, top of the sender. That will vary with the current, since the bimetallic strip is heated by a resistive heater element. The voltage on the sender should be a good measure of temperature, if rather severely non-linear.

Where you may find a problem is if you have an original bimetallic voltage regulator, because then the 10V is nothing of the sort - it's a variable mark-space chopped Vbat, and the sender voltage will follow that shape.

[Pete Lewis]

the joys of an engine driven fan is almost appealing  after all this     whats the improvement ??

Pete

[johny]

Dont do it Pete! The OP just asked for advice not opinions on cooling methods😂

[Pete Lewis]

yes  i get that   it just amazes me why so many supposed upgrades give so much discussion when the triumph designs have lasted 50 years 

i would go with a 3 way switch so you get on  ,auto , off ,     as three options as for switch design  have a browse at places like carbuildersolutions 

Pete

 

[Colin Lindsay]

20 minutes ago, Pete Lewis said:

yes  i get that   it just amazes me why so many supposed upgrades give so much discussion when the triumph designs have lasted 50 years 

Different driving conditions! I used to wonder that, too, but then I can still get into my car and drive for miles without ever meeting another vehicle, and as long as I avoid peak times there are rarely any jams to speak off even in the local towns.

Then I started to notice, whenever I went down the M6 or through some of today's cities, what I was missing... one minute you're at 70 for miles, then suddenly a dead stop for ages, or nose to tail for hours crawling along at a snail's pace. It does test the cooling system a bit.

[PeteH]

4 hours ago, Colin Lindsay said:

Then I started to notice, whenever I went down the M6 or through some of today's cities, what I was missing... one minute you're at 70 for miles, then suddenly a dead stop for ages, or nose to tail for hours crawling along at a snail's pace. It does test the cooling system a bit.

That is "un-joined up Britain". Truck drivers life. 56mph to the next traffic jam, then the customer/scheduler is on the cab phone wanting to know why you missed your "slot". Now their all wondering why young guys and gals don't fancy HGV driving?.

Pete

[Black Cat]

Rights Ladies & Gents, this is my proposal: -

I now have the Revotec fan controller which was on offer at Moss Bros.

Firstly wire up the fan controller as Revotec guide as my earlier post but adding the following additions: -

1.      Modified wiring diagram (Photo 1)

2.      Install a 20amp inline fuse close to the 12 volt battery.

3.      Connect  a new red cable from the fan live to a diode (Photo 2)

4.      Connect the diode to an inline 5amp fuse

5.      Connect the 5 amp in line fuse to an LED warning light and earth the LED light (Photo 3)

6.      Replace the Revotec switch with a simple on off switch rated at 20amps (Photo 4)

Just to clarify a couple of points points: -

1.      The reason I didn’t want to use a toggle switch was the switch is going to be placed in the side of a boxing to cover the gearbox tunnel and I didn’t want a switch which protruded out.

2.      A note on the Revotec wiring layout states the Revotec override switch is only to be used with a Revotec Electronic Fan Controller. Is there any reason why I can't use a different switch?

Hope this is OK, if not let me know please.