Mercedes 208D camper

Are there any knobs missing off the aircon setting buttons and have you tried opening the windows?

No Aircon, windows open makes it hotter in cab.
The Engine, is basically in the cab

You don't explain but I assume the heat is emanating from your engine? demon-tweeks.co.uk do a range of products that could help stop the heat from that source.

cooperman thanks

Only go on holiday in the winter.

I can relate to heat from the engine, as I drove a Bedford van in a holiday job whilst at uni, and the engine was right next to me.

As for the two knobs, I'm assuming that one is the fan and one is the temperature setting,

Usually clockwise is up and anti clockwise is down. You will be able to prove this by checking the fan speed but I would say that
fan full clockwise and the other one, full anti clockwise.

If you don't have it.....
https://www.t2tvmedia.co.uk/books/a040ac/mercedes_benz_sprinter_owner_manual_208d.pdf

Check cooperman's advice, and also look at reflective window film, for all but the cab windows.

Look for a "Kevin & Tracy" screen band, for the top of the windscreen and open all windows as much as is practical.

Get plug in fans for the dash...something like these....
https://www.ebay.co.uk/itm/Portable-Air-Conditioner-Car-Alternative-Plug-Vehicle-Fan-Dash-12V-/153063674359

Change to the traditional VW camper. They have the engine in the back

Have you tried driving in reverse?

The owner of this Merc 208D has found a good way of cooling down:

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It's still a camper van. You can't get much camper than that.

Lady Faye Verrit there are 3 sliding positions of which, two do not have knobs on (missing)

Sports car manufacturers line the engine bay with gold leaf... apparently it's a good way of retaining the heat in the bay stopping it getting into the car. Maclaren might give you some advice, but could be a bit pricey though?

https://www.google.co.uk/search?q=gold+plate+engine+bay+reduce+temperature&rlz=1C1CHBF_en-GBGB726GB726&tbm=isch&source=iu&ictx=1&fir=MMMgoN3hAM_MTM%253A%252CdYwVbIwTgTlsyM%252C_&usg=___o1aCPvPueqMHwQYvPPJDwZ0Kgo%3D&sa=X&ved=0ahUKEwj78IzgybXcAhWkD8AKHXF-C1sQ9QEIKzAB#imgrc=MMMgoN3hAM_MTM:

Lady Faye Verrit i have gone for the fans. thanks for your post

Ooooops!!!

When I said "something like" I didn't specifically mean those!

Ridiculously cheap, and probably tiny!

I'm assuming you have dash vents, so don't you have a good blast of air through those?

the fans are coming fron China summer will be over by then!!