Heater valve...,?

[9two8]

If the heater valve fails will the comb flap ( centre dash vents) stay closed. I have chilled air to the screen but when I use the slider to "Eco" the flap wont open ?

[Alan in AZ]

Quite possibly - if its a vacuum problem.

Windscreen defroster open is the default with no vacuum, as is heater valve open and other flaps closed. Check connections and for leaks...

Alan

[9two8]

Originally Posted by Alan in AZ

Quite possibly - if its a vacuum problem.

Windscreen defroster open is the default with no vacuum, as is heater valve open and other flaps closed. Check connections and for leaks...

Alan

..., thank,s The car stood 6 months in my garage (winter layup) and this year on first start I had a massive misfire situation. Long story short, took it to my mechanic who also rebuilt the gearbox for me about 20 years ago and he removed the fuel tank cleaned it out new filters, Dist cap, rotor, Beru leads silicone vacuum hoses and pipes replaced, etc, etc, Car was still sick, however he removed all the fuel injection components, and checked them thoroughly., basically a top end refresh.., the car now performs brilliantly. It was when I picked it up I noticed the comb flap was staying shut. I removed the air filter assembly and checked the heater valve to see if everything was ok, and there was nothing amiss.

I,m wondering if it was working before all this expensive work as I said it stood 6 months , but distinctly remember it was working previous to the 6 month standing. Iv,e got a new valve in the garage that I always keep handy, it was 4 years ago since I last replaced it. Have noticed when I slide the lever to ECO I can hear a sort of shish noise momentarily.

Any thoughts ?

Ken

[Alan in AZ]

Test for vacuum holding - steady state the vac line to the HVAC should hold vacuum - you will lose a little bit during flap activation - but you should not have a steady leak in any configuration.

You will need a mity vac or similar to test, with this ($50-$60) you should be able to diagnose vacuum problems yourself.

The feed line enters though a grommet in the firewall near the wiper motor - and is fed from a check valve ported off the vacuum line to the vacuum accumulator (in the drivers fender) , there is also the vacuum line to control the heater valve running from the same grommet.

At the HVAC end find the solenoid bar under the HAVC head unit in the console (access from side carpet panels). This is fed vacuum from the line described above - it selectively applies it to the actuators based on the electric solenoids controlled by the head unit slider switches. You can pull the vacuum lines off to test the flaps individually (but test the whole thing first - it may just be a vacuum supply issue).

Alan

[9two8]

Thanks again for your detailed and helpful description,.., must buy a Mity-vac!. In the meantime do you think I should just go ahead and replace the heater valve, and eliminate it, I use the Mercedes valve as it,s identical to the Porsche unit and one third the price here in the UK ?

Ken

[Alan in AZ]

No I'd test it fiirst - if you have no vacuum to it it can't possibly work...

Alan

[9two8]

..., OK thanks

Ken

[9two8]

Originally Posted by Alan in AZ

No I'd test it fiirst - if you have no vacuum to it it can't possibly work...

Alan

Well, it turned out to be the white hard line connection to the vacuum reservoir tank had become detached. Basically you were right, and thanks again

Have ordered a vac tester.


Ken