Can't turn off my heater. Help!
 

My 89 has constant heat coming form the vent on the passenger side below the front windshield. Where do I begin to trouble shoot this?

The vent seems to be constantly feeding out hot air..I can't seem to be able to find the cause.

Please advise.

Have you checked your butterfly 'valves' under the car? Chances are, one is stuck. Could be the cable that actuates it as well.

search on heater dump boxes

follow the big hoses up & ahead of the CV shafts to some round sheet metal things - they will likely have partly open slits showing -- you want those slits to open all the way when the red center console lever is down

there is an adjustment - two 10 mm wrenches on the cable

but they may be way rusted...

my 930 just started behaving the same way. My boxes are not opening up all the way on the drivers side. Thinking of just replacing them with fresh new boxes from our host.