Pontiac Repair: no heat, vacuum leak, pontiac transport

Question
My 1994 Pontiac transport has no heat and wont
change from defrost to any other settings and fan.
Comes on and off when it wants i already replaced
fan realay and control panel  

Answer
Hi Carl:

As far as the blower motor goes. possably a loose connection at the blower resistor or at the motor it's self. those older ones the connection at the motor would overheat and then become aloose connection. As far as the HVAC modes not working. you could have a vacuum leak and that will make the HVAC not cnage modes. on the 3800 engine there are 2 vacuum lines that run from the engine to the body on the right of the van. the hoses crack and split look for a broken hose there. as far ahs heat goes it physically has no heat or just the fact that the blower doesn't work you have no heat?