Hi there
The heaters in my 1978 Pace Car work OK, hot and cold mixer works. AC does not work (will try to solve at a later date.
My problem with interior heaters is the window defrost position works fine as does the floor position.
When I put it in the HTR position no air comes out the vents.
I have pulled the centre console and dash apart (also attempting to fix clock also) and I believe my issue is the flapper (attachment heat1), this flapper does never moves or even tries to move, but I can push it open with my hand which would then route the air through the dash vents.

The second attachment (heat2) works absolutely fine and the flap is operated by the vacuum spring next to it which allows air to either be sent to defroster or the feet.

The third attachment is a diagram of the vacuum system (heat4) and I noticed in my car the vacuum 3 port switch has two vacuum hoses as per the diagram attached and the third one has nothing connected and this is hissing, if I put my finger over it then it interrupts the hissing noise, should this be happening here?

My hot/cold mixer level cable operates fine.
Any advice or solutions please? Should the vacuum 3 port switch be hissing and letting air escape out that third hole, is it a vent or should it be air tight?
Lastly my 8 track player, works, it will play 8 Tracks but sometimes the front right and rear left speakers drop out, especially on rough road and the skip track button does not work. AM/FM work fine and 8 tracks play fine. I think my issues are all round the skip track button as when pressing that button the player makes no attempt to skip track and sometimes pressing it causes interference or those speakers to drop out, like a loose connection, this issue is not present when radio is on and all speakers check out as working fine and all cables at speaker end are fine and all connections at back of radio are fine.
My drive belt is also loose, so I need a new drive belt, anyone know where I can buy a drive belt in UK please and anyone/anywhere that can service/repair these old players. Be nice to keep it as I have a few 8 tracks for it.
Picture attached of the loose drive belt! (heat3)

Any help / advice would be greatly appreciated please.
The heaters in my 1978 Pace Car work OK, hot and cold mixer works. AC does not work (will try to solve at a later date.
My problem with interior heaters is the window defrost position works fine as does the floor position.
When I put it in the HTR position no air comes out the vents.
I have pulled the centre console and dash apart (also attempting to fix clock also) and I believe my issue is the flapper (attachment heat1), this flapper does never moves or even tries to move, but I can push it open with my hand which would then route the air through the dash vents.

The second attachment (heat2) works absolutely fine and the flap is operated by the vacuum spring next to it which allows air to either be sent to defroster or the feet.

The third attachment is a diagram of the vacuum system (heat4) and I noticed in my car the vacuum 3 port switch has two vacuum hoses as per the diagram attached and the third one has nothing connected and this is hissing, if I put my finger over it then it interrupts the hissing noise, should this be happening here?

My hot/cold mixer level cable operates fine.
Any advice or solutions please? Should the vacuum 3 port switch be hissing and letting air escape out that third hole, is it a vent or should it be air tight?
Lastly my 8 track player, works, it will play 8 Tracks but sometimes the front right and rear left speakers drop out, especially on rough road and the skip track button does not work. AM/FM work fine and 8 tracks play fine. I think my issues are all round the skip track button as when pressing that button the player makes no attempt to skip track and sometimes pressing it causes interference or those speakers to drop out, like a loose connection, this issue is not present when radio is on and all speakers check out as working fine and all cables at speaker end are fine and all connections at back of radio are fine.
My drive belt is also loose, so I need a new drive belt, anyone know where I can buy a drive belt in UK please and anyone/anywhere that can service/repair these old players. Be nice to keep it as I have a few 8 tracks for it.
Picture attached of the loose drive belt! (heat3)

Any help / advice would be greatly appreciated please.