On my 2005 Pontiac Vibe the heater fan does not work all the time

it could be a bad blower motor resister that controls fan speed depending on what fan setting you have set the dash switch on.it could also be the blower motor itself that needs to be replaced.with the blower on try tapping the motor and see if it tries to start.if it tries or starts to work then the motor will need replacing.

Remove Blower Motor Toyota Matrix Pontiac Vibe

http://forums.genvibe.com/zerothread?id=23496

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not necessarily could be something else try jumping the fan with direct current from battery and see if it runs could be in fan switch or could be a fuse causing the problem if it does not run with direct current from battery then it is the motor.

replace motor and resistor card

usually the radio and the cig lighter sharing the same fuse make sure it is the right fuse you looked at i check all the fuses

My 2005 Vibe did the same thing it was the heater resistor. It is located to on the firewall behind the glove box on the lower left side of the blower assembly. Two 5.5mm screws hold it in place (1/4 inch socket works too). I used a socket attached to a socket swivel to replace mine in under 10 minutes. Heater now works as good as new. I purchase mine online for $30 from rockauto.

It sound's like you might have a bad blower motor resistor.

Check the fan motor, it is probably going out. Next time it should be running but is not, tap on the fan motor lightly and it may start. If it does, then replace the motor.