No heat but car does not over heat

SOURCE: heat & temp gauge

you have bled air out of system. on top front right of eng. there is a brass bleder

SOURCE: 1999 Pontiac Montana Overheating

sounds like you could have faulty gauges to meby check them out.... and yes its posible that its pluged

SOURCE: possible overheating, 2004 pontiac montana

Its definitly a bad reading, you would know if your vehicle is overheating, you can usually smell it right away.I would say its your temperature gauge sending unit is defective, check the wires to see if they are well connected or broken. ask a backyard mechanic for assistance.

SOURCE: 1996 Pontiac Grand Am overheating

If its the 3.1L it could be your intake manifold gasket , the material used for the gasket does not react well with GM's Dex-Cool antifreeze. The leak may not be apparent at first, but I would pressure test the cooling system. If you look at the front of the motor by the belts , try to peek down at the intake manifold and check for slight seapage to an obvious leak.

If its either of the Quad-4's they were notorious for heads warping or cracking.

SOURCE: car runs hot

CHECK YOUR RELAY IN YOUR FUSE BOX UNDER THE HOOD ON THE DRIVERS SIDE INNER FENDER. THE A/C AND THE HEATER RELAY ARE SAME. CHECK AND SEE IF THE A/C REALY WORKS BY TURNING ON YOUR A/C SWITCH. THE ELECTRIC FAN SHOULD START RIGHT AWAY. OTHERWISE YOU HAVE TO WAIT TILL THE ENGINE ACHEIVES OPERATING TEMP TO KICK THE FAN ON. IF ONE DON'T WORK AND OTHER OTHER DOES... SWITCH THE RELAY AND SEE IF IT WORKS. BEEN THERE AND DONE THAT. $9.00 FOR A NEW RELAY AT CHECKER AUTO PARTS.