Hi folks,
Sorry it's taken me a little while to get involved in this, despite the PMs and tagging in this thread.
We can request the wiring enters the car on either the N/S or O/S. I was thinking N/S so to make life easier.
For a right-hand-drive car, the wiring should be on the N/S, but we're probably best talking about this in terms of left/right. The wiring should enter the car on the left, as the under-floor electronics compartment is always on the left, irrespective of whether the car is a right- or left-hooker. If I was wiring such a system for A2 owners, that's where I'd be doing it.
I see the biggest issue as power. You're talking about 1kW or so? Make it 1.2 for ease of calculations - that's 100A. 1.4s only have a 90A alternator.
Whilst we now know Bret's power-consumption figures are a bit high, I still think he makes a valid point. A 25A current draw isn't negligible, especially not on A2s with the 90A alternator. Even on A2s with more beefy alternators, a cold, dark morning could see the driver asking for the electric cabin heater, rear screen heater, headlights, heated seats, etc. Throw a heated front screen into the mix, and the alternator may be on its knees, begging for mercy. This is probably something that needs thinking about on a car-by-car basis, depending on which engine/alternator/options are fitted.
That's a very basic standard relay circuit. But yes. I would want something resembling OEM which would be simple plug and play.
The wiring diagram posted above is, more or less, how I'd envisaged wiring this in. As far as I'm aware, the goal here is to make it such that the front winscreen switches on/off with the rear screen demister rather than it having its own dedicated button. I can certainly do it with OEM relays, connectors, etc, all located neatly in the proper relay plates, meaning it would all look factory standard, but I cannot see a way of making this plug-n-play. If I'm to be involved in this, then the electrics would have to be installed by me, in much the same way as I'd do any of my other retrofits.
A big negative is it's gonna be annoying if you pay a lot out for the windscreen plus the wiring etc if it were to get broke within a few months when there's a minimum order of 5. Plus any replacement covered on your insurance is just going to be for the original spec
This is, of course, a big consideration. The issue regarding windscreen insurance could probably be circumvented by having a chat with the insurance company and insisting that any future screens are sourced from a particular supplier. However, who is that supplier? Does an A2OC member stock replacements? If so, where? How many? What happens when the supply dries up?
if your wear glasses the fine wires can cause issues
I suppose this is a personal issue and not really a deal-breaker for all, but I absolutely hate driving vehicles with electrically heated windscreens, despite not wearing glasses. I'm often distracted by the weird, diffractive effects that seem to be caused by the matrix of fine wires, especially when driving at night. I'm always keen to see new developments for the A2, and I'm happy to be part of the overall machine to make this happen, but my own A2 will remain demisted by old-fashioned hot air!
Cheers,
Tom