Manual Fan Switch Wiring Query
Discussion
About 9 years ago I made my driver's fan switch rear demist function into a manual fan switch. The switch works fine as it grounds the otter switch supply wire (green wire with pink trace) at the multi-block under the dash, however I never got the indicator LED I fitted to the dash to operate as I wanted at the time. I thought I would sort it now as I currently have the instrument panel out to fix an Araldite failure.
This thread reminds me what I originally did, something else I tried and what I ended up with, which was a compromise to get the dash back together at the time.
1 (What I have) - LED connected to common live on instrument panel and connected to otter switch "supply" wire where manual switch is also connected. The LED only illuminates when fan is manually switched as when the otter switch makes the circuit I recall there is insufficient voltage drop to illuminate it. What I really wanted was a light that told me the fans were on by whatever means...
2 - LED connected to common earth on instrument panel and fed a fans-on live connection from the pink wire at the multi-block under the dash. This worked fine except that the LED glowed above 60 mph due to the generating effect of the fans turning in the airflow. Can anyone confirm a resistor value to resolve this? I didn't and still don't fancy an instrument panel hokey cokey of trial and error?
3 - I think I also tried the following - LED connected to common live on instrument panel and connected to fans "return earth" wire (I don't think it was the otter switch one as circuit logic would not have worked). This worked perfectly and illuminated the LED whether fans were switched on manually or by the otter switch, however once the fans had switched on they never switched off! I didn't think about it 9 years ago but I suspect that the live feed from the dash was probably powering the fan circuit after its own live had been switched off? This being the case am I right in thinking that wiring the circuit like this but adding a diode between the LED and the fans "return earth" wire will stop the dashboard live powering the fans but still allow the LED to illuminate?
Any assistance appreciated whilst the car is apart.
Andy
This thread reminds me what I originally did, something else I tried and what I ended up with, which was a compromise to get the dash back together at the time.
1 (What I have) - LED connected to common live on instrument panel and connected to otter switch "supply" wire where manual switch is also connected. The LED only illuminates when fan is manually switched as when the otter switch makes the circuit I recall there is insufficient voltage drop to illuminate it. What I really wanted was a light that told me the fans were on by whatever means...
2 - LED connected to common earth on instrument panel and fed a fans-on live connection from the pink wire at the multi-block under the dash. This worked fine except that the LED glowed above 60 mph due to the generating effect of the fans turning in the airflow. Can anyone confirm a resistor value to resolve this? I didn't and still don't fancy an instrument panel hokey cokey of trial and error?
3 - I think I also tried the following - LED connected to common live on instrument panel and connected to fans "return earth" wire (I don't think it was the otter switch one as circuit logic would not have worked). This worked perfectly and illuminated the LED whether fans were switched on manually or by the otter switch, however once the fans had switched on they never switched off! I didn't think about it 9 years ago but I suspect that the live feed from the dash was probably powering the fan circuit after its own live had been switched off? This being the case am I right in thinking that wiring the circuit like this but adding a diode between the LED and the fans "return earth" wire will stop the dashboard live powering the fans but still allow the LED to illuminate?
Any assistance appreciated whilst the car is apart.
Andy
You dont win with just an ordinary diode, as the voltage flow will still be in the same direction to the LED on the panel be it from a rotating fan, or the 12 volt switched supply. The only device you could use here is a zener diode at say 10 volts, so there would be no current flow unless over 10 volts was available, hoping the fan would not generate more than this. You could use a very high power diode in the fan supply wire that would block any reverse flow, not that Id do this as its a single point of failure that will kill the cooling if it blows. Old skool method would be use a relay to switch the LED, as its unlikely the fans will generate enough to close the relay contacts.
To stop the glow, simply put the led in the coil of the relay circuit You can do that in the footwell. Pop the cover off the relay and connect there. There is no generated voltage in the coil circuit . You can do the override switch from the relay and have the led indicator, no need to open the bonnet!!
Griffit said:
About 9 years ago I made my driver's fan switch rear demist function into a manual fan switch. The switch works fine as it grounds the otter switch supply wire (green wire with pink trace) at the multi-block under the dash, however I never got the indicator LED I fitted to the dash to operate as I wanted at the time. I thought I would sort it now as I currently have the instrument panel out to fix an Araldite failure.
This thread reminds me what I originally did, something else I tried and what I ended up with, which was a compromise to get the dash back together at the time.
1 (What I have) - LED connected to common live on instrument panel and connected to otter switch "supply" wire where manual switch is also connected. The LED only illuminates when fan is manually switched as when the otter switch makes the circuit I recall there is insufficient voltage drop to illuminate it. What I really wanted was a light that told me the fans were on by whatever means...
2 - LED connected to common earth on instrument panel and fed a fans-on live connection from the pink wire at the multi-block under the dash. This worked fine except that the LED glowed above 60 mph due to the generating effect of the fans turning in the airflow. Can anyone confirm a resistor value to resolve this? I didn't and still don't fancy an instrument panel hokey cokey of trial and error?
3 - I think I also tried the following - LED connected to common live on instrument panel and connected to fans "return earth" wire (I don't think it was the otter switch one as circuit logic would not have worked). This worked perfectly and illuminated the LED whether fans were switched on manually or by the otter switch, however once the fans had switched on they never switched off! I didn't think about it 9 years ago but I suspect that the live feed from the dash was probably powering the fan circuit after its own live had been switched off? This being the case am I right in thinking that wiring the circuit like this but adding a diode between the LED and the fans "return earth" wire will stop the dashboard live powering the fans but still allow the LED to illuminate?
Any assistance appreciated whilst the car is apart.
Andy
None of the above methods will inform the driver that a supply and return are present at the cooling fan motorThis thread reminds me what I originally did, something else I tried and what I ended up with, which was a compromise to get the dash back together at the time.
1 (What I have) - LED connected to common live on instrument panel and connected to otter switch "supply" wire where manual switch is also connected. The LED only illuminates when fan is manually switched as when the otter switch makes the circuit I recall there is insufficient voltage drop to illuminate it. What I really wanted was a light that told me the fans were on by whatever means...
2 - LED connected to common earth on instrument panel and fed a fans-on live connection from the pink wire at the multi-block under the dash. This worked fine except that the LED glowed above 60 mph due to the generating effect of the fans turning in the airflow. Can anyone confirm a resistor value to resolve this? I didn't and still don't fancy an instrument panel hokey cokey of trial and error?
3 - I think I also tried the following - LED connected to common live on instrument panel and connected to fans "return earth" wire (I don't think it was the otter switch one as circuit logic would not have worked). This worked perfectly and illuminated the LED whether fans were switched on manually or by the otter switch, however once the fans had switched on they never switched off! I didn't think about it 9 years ago but I suspect that the live feed from the dash was probably powering the fan circuit after its own live had been switched off? This being the case am I right in thinking that wiring the circuit like this but adding a diode between the LED and the fans "return earth" wire will stop the dashboard live powering the fans but still allow the LED to illuminate?
Any assistance appreciated whilst the car is apart.
Andy
David Beer said:
To stop the glow, simply put the led in the coil of the relay circuit You can do that in the footwell. Pop the cover off the relay and connect there. There is no generated voltage in the coil circuit . You can do the override switch from the relay and have the led indicator, no need to open the bonnet!!
No this doesn't work as it should, I deleted my post from above earlier as I had overlooked something, you have overlooked something.The whole job revolves around an LED wired directly to the supply and return terminals of the radiator cooling fan so as to prove that the supply and return are there when they should be
I now have the solution
Edited by Penelope Stopit on Friday 13th January 08:26
David Beer said:
Sorry, you can have it all from the relay. Done many.
No need to be sorry, but there really is a need for people that are carrying out electrical work on anything to understand what needs to be achieved so as to end up with information circuits working in the best possible wayYour method is not the correct way of giving the best possible information and I am amused that you have carried out this work on many vehicles and possibly charged for that work when the end information given by the dash mounted LED or Bulb using your method is not good enough information
Your method is only informing the driver of the vehicle that power is being supplied to a relay coil
Having spent some time on this I now have in front of me a circuit to inform the driver that a supply and return is present at the cooling fan motor terminals, this information is what I and many other drivers would want from a cooling fan circuit
The OP has asked the question but has not returned here, I will wait and see if the OP returns before going any further with this
Edited by Penelope Stopit on Friday 13th January 08:27
Still here and reading with interest as it is the weekend tomorrow, which may mean I can look at this.
I've not tried connections at the fuse box before because the multi-block was right there in front of me with the instrument panel removed and it was too easy not to connect there.
Look forward to further variations on the theme and appreciate the risk of adding the diode to the fans power feed (pink wire).
I've not tried connections at the fuse box before because the multi-block was right there in front of me with the instrument panel removed and it was too easy not to connect there.
Look forward to further variations on the theme and appreciate the risk of adding the diode to the fans power feed (pink wire).
Penelope Stopit said:
No need to be sorry, but there really is a need for people that are carrying out electrical work on anything to understand what needs to be achieved so as to end up with information circuits working in the best possible way
Your method is not the correct way of giving the best possible information and I am amused that you have carried out this work on many vehicles and possibly charged for that work when the end information given by the dash mounted LED or Bulb using your method is not good enough information
Your method is only informing the driver of the vehicle that power is being supplied to a relay coil
Having spent some time on this I now have in front of me a circuit to inform the driver that a supply and return is present at the cooling fan motor terminals, this information is what I and many other drivers would want from a cooling fan circuit
The OP has asked the question but has not returned here, I will wait and see if the OP returns before going any further with this
So I had a look at this today and am not sure that I had done what I thought I had in (3) above 9 years ago as it just didn't seem to test out (until my multimeter battery went flat Your method is not the correct way of giving the best possible information and I am amused that you have carried out this work on many vehicles and possibly charged for that work when the end information given by the dash mounted LED or Bulb using your method is not good enough information
Your method is only informing the driver of the vehicle that power is being supplied to a relay coil
Having spent some time on this I now have in front of me a circuit to inform the driver that a supply and return is present at the cooling fan motor terminals, this information is what I and many other drivers would want from a cooling fan circuit
The OP has asked the question but has not returned here, I will wait and see if the OP returns before going any further with this
Edited by Penelope Stopit on Friday 13th January 08:27
). One way or another the dash is going back together tomorrow as I've a respray, hood and carpets booked from next friday!Having looked at the fusebox for a connection the two things that strike me are that I really should chop out all of the excess loom one day and why didn't I move the battery behind the passenger seat when I had the body off?! Probably something to have done before the interior and paint but a bit late now.
Any further clues welcomed!
blitzracing said:
You dont win with just an ordinary diode, as the voltage flow will still be in the same direction to the LED on the panel be it from a rotating fan, or the 12 volt switched supply. The only device you could use here is a zener diode at say 10 volts, so there would be no current flow unless over 10 volts was available, hoping the fan would not generate more than this. You could use a very high power diode in the fan supply wire that would block any reverse flow, not that Id do this as its a single point of failure that will kill the cooling if it blows. Old skool method would be use a relay to switch the LED, as its unlikely the fans will generate enough to close the relay contacts.
This needs saving here in case the poster decides to delete the originalThis is a classic
Mr Plow said:
Penelope Stopit said:
Mr Plow said:
Can anyone provide an idiot's guide to stopping the LED coming on above 60mph?
I have the same challenge as the OP.
Cheers
Email me atI have the same challenge as the OP.
Cheers
PenelopeStopit@tutanota.com
I must get PH to edit my email address
Post back here and comment Email sent
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