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September 2006

Heated Windscreen

Fitting the windscreen is fairly easy - just follow the instructions in the Tiger manual for fitting a conventional (i.e. non heated) windscreen the important thing to remember is to drill the holes to allow the power cables to pass through the scuttle into the dashboard area. If you forget this stage well it isn't worth proceeding any further.

Basic wiring the windscreen has two wires one connects to a power feed and the other connects to an earth point so feed a wire from the switch to the screen and job done! Er no. The windscreen draws 14A which would melt most switches and could result in a fire. What we need is a relay, at this stage I could have just gone out and bought a conventional 30A auto relay and wired this in. However this to my mind has a major disadvantage in that it would be easy to forget the screen was switched on. So I needed a timing relay. After a lot of fuss and bother I finally located one from www.vehiclewiringproducts.co.uk

This relay has a small timing device built in so once it has been triggered it will stay closed for 10 minutes before opening again - perfect for the forgetful driver. At the same time I also bought one of their modular relay and fuse bases to give me something to wire the relay onto. The part numbers for these items are RS3F (~2 each) and GLR10 (~9.20) the prices are approximate so check their website for the latest costs. You will also need some 25A minimum cable to connect the relay to the screen and a 20A fuse.

Installation - the installation is fairly straightforward as the standard tiger loom provides a lot of the connections you will need.

  1. For the power to the fuses and relay take a feed from the auxiliary (small yellow) terminal on the ignition switch. This will give a power feed when the ignition is turned on and more importantly it is killed when operating the starter (running a heated windscreen and a starter motor at the same time will overload the power available on the car).

  2. For the switch trace out the original heater control wires - it is a small bundle of three cables loomed together a power feed from the car and two wires one for low speed and one for high, we are only interested in the power and the low speed cables.

  3. Once you have obtained these wire up the unit as shown in the diagram below.

  4. For the warning lamp you can either install another warning lamp into the dashboard or rewire the existing switch lamp to operate at the same time as the screen is switched on.

  5. Because the base that I bought has three spaces for fuses and I had only used one I also wired up the other two fuse bays - one I used to feed the cigar lighter (useful for battery chargers) and the other feeds my speed camera detector - it is a lot easier to do this out of the car on the workbench rather than fiddling about under the dashboard!

Wiring Diagram:wiring diagram

Operation - using the existing switch on the dashboard switch it on and off again this will create the pulse needed to start the timing circuit running. If everything is working correctly after a minute or so the glass will become warm to the touch and then shortly after become hot. If in the meantime you wish to turn the screen off I haven't yet worked out how as the relay needs to lose power apart from turning the ignition off to lose the power feed to the relay.

Future modifications - one thing if I can locate one is to change the switch from a conventional rocker design to a momentary switch so it will automatically reset rather than having to operate the switch twice myself.