Got a Mk 1 GTi Cabrio heater problem... sound familiar?

[will2003]

Hello!

Finally registered here after visiting a lot, what a great forum!   

Just bought myself a G reg 1800 GTi Cabrio, and absolutely love it, bar one problem that I can't understand...

Regardless of how you set the hot-cold slider on the heater controls, the vents that run along the dashboard front, for heating the windscreen, always pump out hot air - is that normal? Does the hot-cold slider not affect these vents?

Secondly, when you set the fan to blow from the two vents that face the driver and the passenger, it always blows very slightly warm, regardless of where you set the hot-cold slider... not looking forward to this in winter, that's for sure. What causes this problem? Is it the wire / cable things that have come dislodged (maybe by my stereo install), or is it something more complex in the inner workings behind the gearstick console thing?

I also notice that sometimes the windscreen steams up in seconds, randomly, while driving - as if water somewhere inside the heater system has come into direct contact with hot metal.

It absolutely poured with rain today, and the first corner I took when I drove it later in the day made a trickling water sound somewhere in the front area of the car... could this be a summer's worth of leaves blocking something up in the bulkhead area and causing water to colllect where it shouldn't, maybe casuing the problem above too?

I'm full of guesses but would love to know if any of you have any tips or suggestions.

Cheers!

Will

[richandhazel]

Hi and welcome.

The heater control operates a valve in the engine bay, that controls how much coolant flows through the matrix. You can manually operate it, look for 2 pipes going through the bulkhead, one of the pipes will have said valve on it. Check to see if moving your slider is making the valve operate. If it is then it could be the valve itself is faulty.

[richandhazel]

If your scuttle drains are clogged then it is possible that rain water could find its way into your heater via the fan intake. However another common problem is for the heater matrix to leak........you end up blowing coolant onto your windscreen.....are you losing any coolant?

[will2003]

Thanks for the quick responses guys, much appreciated!?

I took off the flimsy plastic cover thing that runs along the bulkhead and surprise, surprise it was absolutely packed with sludge and leaves, to a point where water was just filling up in there, high enough to actually enter through that white plastic mesh box thing, so I'm guessing that's why the car was steaming up from the inside? Cleared it all out, and even found that rubber drainage pipe / plug thing on the passenger side of the bulkhead was completely blocked up too. Cleared it all out and now rainwater has an easy and quick way to drain out of that area safely Am I right in thinking that is the only drainage hole in the bulkhead area? There isn't one on the other side of the bulkhead anwhere that I missed?

I also found the valve thing you mentioned - now, when I move the hot-cold slider control the cable is indeed moving the metal arm on the valve, but whatever position the metal arm is moved to (this should be opening and closing the valve, right?). the vents still just blow tepid.

As I mentioned before though, the vents along the front of the dash that blow onto the inside of the windscreen blow really hot, again regardless of how the hot-cold slider is set...

Does that valve control the heat of both the windscreen vents *and* the other vents that face the driver and passenger? Or are the windscreen vents designed to get a supply of hot air regardless of how the controls in the car are set?

If the windscreen vents blow hot or cold depending on how you set the hot-cold slider inside the car, then my problem is twofold - firstly, the valve is permanently stuck open, hence the hot air coming from the windscreen vents, and secondly when you set it to blow through the vents that face the passenger and driver, the hot air is getting lost somehow, and only tepid air makes it through... could the plastic pipes that connect these vents to he heater box be cracked or badly connected? I know the previous owner had the dashboard out to fit an immobiliser

Many thanks again guys, sorry for the essay!

[richandhazel]

I should know this but without taking the cabrio for a spin I can't remember whether the dash vents should permenantly blow cold or change IAW heater slider position. I've got a feeling the centre ones should always blow cold and the side ones should be IAW heater position.

Regardless, I think your valve is faulty. Its basically stuck open, hence you have heat on the windscreen all the time. When you move the slider to cold, the valve should shut preventing coolant from circulating through the matrix. Yours isn't doing that. Fix that first and then I suspect the rest will all behave as normal.

There is a scuttle drain each side, so if you have only found one, you need to dig out the one on the other side. You really don't want water building up in the scuttle area. For a start it will rust and more importantly all your electrics, fusebox etc are located underneath on the passenger side: water/electrics

[will2003]

Thanks again - been under the bonnet all day and replaced the valve - now it works beautifully

I also found that the carpet under the mat on the passenger side was soaked - it's been raining very heavily for 3 days now in London, and as I was saying before the bulkhead area was so clogged with rotting leaves etc there was literally 3/4 of an inch of collected water sloshing around there. In a case of such bad blockage and collected water in that area, could water get inside the car and down into the footwells, causing the damp carpets in the passsenger footwell?

Oh, and a quick consultation of the user manual revelaed all - the two vents that blow onto the driver and the passenger always provide cold / fresh air, regardless of how you set the heater... classic case of RTM Sorry to wate anyone's time on that one...

Nice one for your help 

Will.