Heater fan mists windscreen

Greetings. My first post and it's with a problem:

When it's been raining my heater fan blows moist air on my windscreen instantly misting it up. Not great on the M6.

Any suggestions?

you may have a leaking heater matrix, so the hot air is picking up all the moisture from it.

Look on the passenger side wing, there should be a vent there screwed to the wing top. If it's got some standing water in there, take the vent off and clean the drain tube at the back of the space under the vent to let the water out.

If it's not that, then yer heater's probably for it

Thanks, I'll give that a try. Bit more background:
happened a while a go and my local landy friendly mechanic stuck his arm under the bonnet and cleared some gunk out of a rubber drip valve? Said they always got clogged up and that the valve is to separate water from the heater. Does this make sense?

yeah, under the wing, under the vent is a big duct thing. There is a rubber pipe coming out of the bottom of that.

Thats the drain pipe to let the water out of the heater intake, they do get blocked.

I wouldn't rule out the heater matix leaking though.

Thanks. I'll attack the drain pipe at both ends and cross my fingers. Any easy way of knowing if the heater matrix is leaking?

Erm... Not really. Check the duct is dry, if it still steams up it probably is.

Try radweld in the system, follow the bottle instructions but don't burn yourself on the filler cap when you open it - they are pressurised when hot.

Radweld does work though, and it will fix a small leak quite happily.

if your matrix is leaking you usually get a smell that it similair to what your rad smells like when you take the cap off, you know slightly sweet smell.

Yep. It's gonna be a blocked drain in the bottom of the intake pipe.

Had a go at the drain pipe in the intake - quite a bit of water came out. The pipe itself seems to be almost flush against the wheel arch. No wonder it gets blocked. Is this normal? Should I take a stanley knife to trim it back a bit to let it drain more freely?

The rubber tit on the end of the drain is supposed to act as a 1 way valve, letting water out whilst preventing under-bonnet fumes being sucked into your heater. If you trim it, you'll get fumes in the cabin.
The rubber hardens over time and it stops working effectively. You can try either replacing it with a new one or finding some other type of 1-way valve to fit in its place.

mine is nipple-less - that would explain why you can smell h ot oil in my cabin!

How did you get on rjj, was it the intake?

I had the same problem when i went into deep water. water went down vent and into the heater.
The instance i turned on the blower, windscreen misted up.

solution was to feed a piece of fish tank tube into the fan area from the vent on the front wing and syphone the water out.


pm me if more details needed

daz

Gave the drain valve a squeeze and a good few mls of water came out. Didn't seem to be blocked. Has done the trick for now. The rubber (is it rubber or plastic) of the drain valve felt very stiff and I don't think it would let water through so I'm keeping an eye on things for now. Got leaks to deal with now...

rjj said:

Had a go at the drain pipe in the intake - quite a bit of water came out. The pipe itself seems to be almost flush against the wheel arch. No wonder it gets blocked. Is this normal? Should I take a stanley knife to trim it back a bit to let it drain more freely?

Click to expand...

Had a look at mine and its the same thing. Tight up against the inner wheel arch. Gave it a squeeze and got what looked like a pint of water so took the whole air intake out and cleaned it properly.
Amazing what you find when you go looking. Never knew I had a drain on the air intake.