i've got a 68 coup that has the heater on all the time. i can't turn it off.what gives? i've met other mustang owners at car shows and some of them have the same problem.could it be the cable for the controls are broke?it's a pain when it's hot out and u don't have A/C. isn't there a lever to open a vent to let in outside air? any help is greatl appreciated. thankyou very much.

 

Could be several things. First, I would check all your vacuum line connections under the dash, if your diaphragm isnt opening or closing properly, that could cause constant heat.

Second, open the hood and check the water heater control valve which should be mounted against the firewall on the passenger side. Check to see if the vacuum line is attached, the valve may be old and not operating correctly, which could give a constant supply of hot water to your heater core.

There is a fresh air vent, there is a black **** underneath the dash directly below the steering column, it is cable operated and can open and shut the fresh air vent. . Hope this helps.