Well, after T7Design came to nothing I thought if you want a job doing properly - do it yourself.
My heater didn't provide any heat. It provided air, and heat was getting to the heater through the coolant so it was pretty clear the issue wasn't air leaking, but the flap in the heater not working. But I thought what's the point in fixing it when so many others have failed before me, and T7 Design will have a new heater....er....soon?
Reading through the various heater threads it's clear that the rad is up to the job and so is the fan. The box is $hit and so is the ducting. So I thought I'd remove the box, connect the inlet and outlet radiator hoses together so I can still use the car, and then make a heater box myself, using the existing rad and fan.
So I take the heater box out (why do Lotus insist on having a clearance of 0.0000001mm for everything) and have a look at it before I start to dismantle. It's actually in good shape without many gaps. There's also not much crud in it. The car had 14k miles on it when I bought it last year and the previous owner clearly didn't use the heater much because it doesn't work!
It was clear what the problem with the flap was. The join of the two halfs of the heater box was catching the flap, stopping it move. Someone had tried to force it (probably me) and so the flap control had broken. So I'm thinking - why not put it back with it left on hot?
Which is what I did, and now I have heat. Not a huge amount, and it's 10°C outside when I tested it, not -10°C so my opinion may change, but it makes the car useable over longer distances in winter, which wasn't the case before.
Funny, I never had much of a problem with demisting before. As the cabin was so cold it wasn't so much of an issue. Yes, now it takes ages to clear. Will just have to keep a cloth in the car - which I always have done anyway. De-icing isn't such an issue for me as it's mostly garaged.
I am still looking for an upgrade. The original ducting is awful and I think I'll get some good stuff from T7 design, and while I'm at it I might upgrade the heater like trevvx220 did: -
I don't think the flap will ever work properly so I'll probably add a water control valve and use that instead.
I need to properly wire in my sat nav and I'll silicon the cabin ventilation ducting at the same time.
I will also insulate the pipe to the rad when I change to winter tyres soon.
All in all, wish I'd done this last year, and if the T7Design thing wasn't in the offing I would have done.
on the flip side it did also pull too much heat from the cooling system :s
Kind of "supplementary heater". Interesting.
for a bit of outside the box thinking though.
btw check your brake/clutch fluid
