408: A lot of heat coming through the firewall.

[Giles]

Yes, to jump on a bandwagon - I had this too and the heater was constantly on. Drove from England to France in July and it was a bit of sauna.

If it's coming out from the heater, I'd check that the heater valve is working (not constantly on) and that the heater flaps are opening and closing.

You can also take the heater apart and check that the seals on it do close properly. If you are refurbishing it, the heater core is I think the same as one of the sprites.