heater control vacuum loss

[Chas54]

I have been tracking down vacuum leaks whilst I have had my intake plenum off and now only have the heater controls to check. At the moment I have the vacuum connection from the plenum to the heater system reservoir plugged so I can do my setting up . I have tried pulling a vacuum on the reservoir with the supply to the heater switches pipework pinched to seal, and its ok. When the heater switches are tested , they wont hold a vacuum. The water valve and actuator are OK when tested. So I have a leak across the heater switches and system in the dashboard . I cant think why this would be normal , and it looks a nightmare to get at the bits. Anyone come across this problem before?

regards
Charlie

[Fredjohn]

Charlie
Don't know if you've looked at them, but there are some very good pictures in the workshop manual for either the 4 or 6 position switch system. Available in the Manuals tab section at the top of the page, when logged in.

I spent hours looking at it before I figured my lose pipe issue. If you remove the radio, you can just about get a hand in to feel the pipes and connections.

Problem is it could be either a split pipe or a lose pipe.

Silicon (3mm?) tube is the generally recommended replacement.

[Simon_P]

There is a bleed in the rotary switch by design. I think if you turn it to recirculation it will be blocked.
This applies to the 6 position switch, I don't know about the 4 position switch. When I fist got the Elan I was trying to fix the vaccum leak and took the rotary switch to pieces - one part of the switch is a labyrinth, the other has the holes as you move the labyrinth it connects the appropriate holes.
So if the flaps move as you rotate the switch it is OK

[Blaster]

On mine it was one of the hoses going to the face level flap had partly come off causing a leak.

I connected a vacuum pump to the manifold connection then with a bit of small bore hose in one ear moved the other end around to listen for the leak. Using a pump kept the noise down making it easier to listern.

[Chas54]

Thanks for the replies .
I found the drawing showing where the pipes go to the flaps etc but...
Simon P advised that the control switch is a labyrinth with bleed holes and that if I put the 6 position switch to the recirc position, it should seal. Just tried this and I can pull a vacuum on the hose to the reservoir now.
So the loss in vacuum appears to be a designed in loss .
Anyway I am now happy having searched all other areas whilst I had the plenum off. Found the hoses to the 2ndry throttle solenoid the wrong way round.
Ive just got to do some setting up now, ive changed the IAC as it was badly pitted and I think it was slow to operate.
I had the distributor ? off to check for play etc having seen the advance wandering about at idle. It all seemed fine to me though and its now back on and the base timing checked with the strobe in service mode.

Thanks again

Regards
Charlie