Thanks Chris I think that the air con is working ok I am trying to confirm whether it is the HBV leaking before stripping out scuttle or inlet and plenum as suggested by Darth.
Yes. In order to confirm the hbv leak is leaking, you need to;
1) find it
2) see if it leaks
3) if confirmed leaking, replace it.
1) follow the vac pipe from the heater pipes in bulkhead. This leads to the hbv hopefully.
2) to test the hbv you need the engine running, which means leaving the engine parts in place, and cycling the cc from hi to lo with hand/s on the hbv each time to see/feel if it leaks.
3) once confirmed as leaking, Daz suggests removing the plenum as said. I prefer to remove the scuttle and re seal it, insuring its water tight and doesn't drip on your coil pacs. Marks Dtm suggests replacement by removing nothing but the hbv. Choice is yours.
The vac pipe from heater matrix pipes on bulk head attaches to the top of the hbv and the cc uses this via vacuum to switch the coolant flow away from the heater matrix via the hbv. This is the sole purpose of the hbv. With cc on lo the coolant flows one way through the hbv. With cc set to hi through the other coolant way in the hbv. So by switching the cc from hi to lo you are able to test both the water "ways" of the hbv.
Just to clarify
