JST Posted November 24, 2012 Share Posted November 24, 2012 i have a fog light switch from a td5 defender which i would like to fit into the spare slot on a Puma Defender. i would like to use it to power the electric heated door mirrors. does anyone have the knowledge to know which wires would be needed to switch a relay for the mirrors. i guess it needs a const 12v supply to replicate the feed which would of been the lights on, i was going to wire in an ign feed for this. the switch doesnt latch, so i guess its just repetitive pushing for on then off or does it go off when ign feed is lost? i have 4 wires on it red/yellow black/grey black red/orange would welcome any help i am not too good with wiring diagrams! Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted November 24, 2012 Share Posted November 24, 2012 Unfortunately the switch is just a simple momentary switch. It provides a connection to earth when pressed down but that is it. The actual function of connecting the fog light to power is done by a small ECU in the dash, Luckily for you the functionality can be replicated with a simple latching relay. Wire it so that it is "pulsed" to earth by the fog light switch and then it will provide power to your mirror heaters. This is similar to how the heated screen functionality works. I think, off the top of my head, the wiring is as follows: Red/yellow - 'On' light, fed from fog light ECU Black/grey - Connection from ECU to switch Black - Ground Red/orange - Illumination So basically you need to supply one side of the coil (latch) circuit of your latching relay with 12V (ignition-switched), and feed the other half to the black/grey wire on this switch. This way when you press the switch, it will momentarily energise the relay, switching your heated mirrors on or off. Or you could use another switch that latches, and swap the fascia over. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted November 24, 2012 Share Posted November 24, 2012 Is the Td5 switch different to the previous ones then? Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted November 24, 2012 Share Posted November 24, 2012 James is referring to the 2002-onwards switch when he says Td5, 1999-2001 Td5s had a column fog light switch as per previous models. Quote Link to comment Share on other sites More sharing options...
landroversforever Posted November 24, 2012 Share Posted November 24, 2012 ahh of course. I hadn't thought of that Quote Link to comment Share on other sites More sharing options...
Troll Hunter Posted November 24, 2012 Share Posted November 24, 2012 JST, Wouldn't you want your mirror heaters to switch off after the frost/ice has cleared? It's probably better than relying on your memory to turn them off. If this is the case, then a timer facility, such as is used for heated rear windows, might be appropriate. If it switches them off too soon, just press the ON button again. However, be very wary of any of my electrickery comments, I'm no auto electrician. My skill set ends at operating a light switch! Mike Quote Link to comment Share on other sites More sharing options...
JST Posted November 25, 2012 Author Share Posted November 25, 2012 cheers for the replies guys. very informative and quick. so either a timer relay or a latching relay would be required. any recommendations for either? Quote Link to comment Share on other sites More sharing options...
western Posted November 25, 2012 Share Posted November 25, 2012 mine are just on a on/off switch, no relay, they only need to be on for around 3 to 4 minutes. Quote Link to comment Share on other sites More sharing options...
mmgemini Posted November 25, 2012 Share Posted November 25, 2012 When I bought me mirror heater elememts from Ploughman Bros I was told to use an ordinary switch with a relay. No timer relay. As the mirror heater would need to be on longer than a heated windscreen. I use a switch with a warning light. Also I use my mirror heaters in wet weather which keeps the glass clean. Quote Link to comment Share on other sites More sharing options...
Retroanaconda Posted November 25, 2012 Share Posted November 25, 2012 Latching relay: http://www.vehicle-wiring-products.eu/VWP-onlinestore/relays/relays.php#latch Wouldn't bother with a timer function. As above, it's useful to have them on all the time in rain as it keeps them clearer. Quote Link to comment Share on other sites More sharing options...
JST Posted December 4, 2012 Author Share Posted December 4, 2012 cheers guys, just getting around to sorting this out now! Quote Link to comment Share on other sites More sharing options...
ejparrott Posted December 4, 2012 Share Posted December 4, 2012 Rumour has it that BMW's have heated rear screen and mirrors on constantly. I don't know how true it is, but someone with a modern BM would know whether there is a switch for it. My source says there isn't, because they're always on there's no need for a switch. That only works on the assumption that they can handle that amount of use. Quote Link to comment Share on other sites More sharing options...
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