Pontiac Problems? Ask a Mechanic for Answers ASAP
The most likely cause of your problem would be a restricted heater core, you can backflush it yourself. If that is not it would be a problem with your door switching from hot to cold. But my money is on the heater core. Does your car get up to operating temperature which should be about halfway on your gauge? If so remove both hoses from the heater core take a water hose and force water both ways until you get a good stream of clear water
Hey no problem, okay when you pop your hood look straight back on the firewall, that is the part where your master cylinder and brake booster is you will see two rubber hoses going inside those hoses hook up to your heater core a heater core is just like a little radiator water flows through it hot and a fan blows air over it and give you the hot air inside. What happens is they stop up and want let water flow through. SO you want to unhook both of those hoses and take you a garden hose hold up to the pipe and force water through and then do it through the other pipe this backflushing will clean it out. then just hook your hoses back up and you have heat.
Sir have you had a chance to check this, or can i help you further