Vapor coming out of dash when air condition is on

If the dash has to come out then it has to come out.

air conditions work by removing water vapor from the air
that water is collected in a tray to be drained out
if the drain is blocked then that water will run out onto the floor

"Vapor lock" is a condition that occurs when fuel becomes heated to the point of evaporation. If your vehicle is truly vapor locking, it means that something hot is coming in contact with your fuel line somewhere, overheating the gasoline to the point of it vaporizing. This is HIGHLY UNLIKELY. If you truly do have a vapor lock condition, find out where the fuel is becoming heated and fix that condition.
On a 1997 Jaguar XK8, it is FAR more likely that you have a bad fuel pressure regulator or a bad ICU.

The coolant is not evaporating ,it is leaking from the heater core. The vapor out of your vents is coolant. You probley also have a residue on the inside of your windshield

Sounds like you may have condensation in the vent channels. However, not sure how much of an issue it is.

If it were a heater core, you'd notice the coolant smell and fogging up of the windows ONLY when your heat is turned on, not cold air, because when you turn up the temperature, a door adjusts to direct air through the heater core and if it's leaking there, that's when the vapor comes.

So, with it being cold and having vapor, my question is now this: is it constant? Did you have it on heat and then switch it to cold? A temporary burst of vapor shouldn't be anything to worry about. Something more constant sounds like something that should be diagnosed by a tech.

Several things can cause this but start by verify the choke pull off which is responsible for opening the choke plate after engine has started.It will recieve engine vaccum once started and open to allow air into the carb. This is a vacuum dash pot/pull-off externally mounted to the carb with a linkage arm to the choke plate.Without this opening,the engine will be starved for air and put you into a full rich condition. Another external device wchich can mysteriously cause rich conditions is the canister purge valve. It can introduce raw fuel and vapor on start up when failed.It is a black plastic valve near the carb with small and large vacuum tubes.

Check the plenum door motors (vacuum controllers). When you move control you should see each of them move. the one that does not respond is the one that isn't working. Check hose that feeds it as well if no vacuum there switch control is bad.)

Most likely the condensor...not the evap. Get a good AC&R auto shop to install ClipLight sealant...problem solved.

your air conditioning system needs recharged. im sure of it.

if this vapor fogs up windo its a heater core problem have to replace or bypass it two hoses run to the fire wall to the inside disconnect them get a fitting to run them to gather and see if u still have problem