No hot air from vents at higher speeds

[alecT25]

I seem to have a nicely working interior heating system, heater blows out hot air nicely. However, at higher speeds on the motorway there seems to be so much air blowing through all the vents/system that the warm air is lost in the huge amounts of cold air blowing in from outside. All the levers seem to work correctly and I can regulate how much heat is coming out and which vents it goes to, when driving around town. I don't seem to be able to completely close off the vents, as there is also a really annoying whistling of the air at higher speeds. The van is a converted panel van 1986, Watercooled DG engine, so from investigating other posts it would seem that I would only ever get cold air from the side vents anyway?
Is there something missing in the system that should let me close the vents down to the outside as it would seem this might be the problem or is it something else?
Any help gratefully received.

Thanks

[bigherb]

It is either the cables are not adjusted correctly and the flaps are not shutting or likely the foam seals on the flaps in the heater box have crumble away.

[alecT25]

Thanks for the response.
Do both of those options require removal of the dashboard to investigate, or is there an easier way to find out without going through that?

Thanks again

[bigherb]

The cables can be adjusted without removing the dash undo the clamps or spring clips holding the outer cables to adjust
This an air cooled engine heater box but water cooled are similar.


The dash and heater box has to be removed to replace the foam you usually find something like this.

[alecT25]

Thanks for the pictures, that's a great help.
Will have a go at tightening the cables, hopefully that's the issue.
If it is the foam that needs replacing do you know whether I would I need to get a new heater box, or is the foam a part you can get? Searching online for that doesn't give any results that look particularly promising.

Thanks again for all the help.

[ghost123uk]

Just to add, as far as I am aware, the side vents on the dash, the ones that face rearwards, are fresh air only, i.e. not heated. They turn on/off with a thumb-wheel type control on the actual vent. Guessing you knew that, but just in case

Re the foam. You just have to be imaginative here. Draft excluder foam has it's uses, and also you can buy it off a roll at some market type places etc. E D I T = or Ebay of course -> http://www.ebay.co.uk/sch/Vehicle-Parts ... et&_sop=15" onclick="window.open(this.href);return false;

[silverbullet]

85/86 is changeover for heaters. Later ones had heated air feed to the dash ends.

[ghost123uk]

85/86 is changeover for heaters. Later ones had heated air feed to the dash ends.

Good info
Mine is a late 85 and seems to have mostly "MKII" parts, but I have "MKI" dash vents

[silverbullet]

My syncro us the same. Built Dec 85, late type sliders etc but early heater, which I have recently (for me) changed.
Now I am struggling to locate the correct later elbows & hoses...