2005 trailblazer fan motor vibrates whole dash

Your heating system is broke in the dash. The doors or gates that change where the air is to go, has a broken hindge or actuator. Your heat is set to defalt to the defrosters as a safety thing. The vibration, I would say, is your fan & it may have been the thing that started your whole problem. The fan has something wrong W/ it, weather it has dropped, the shaft that it runs on is bad, or it is just going to the bad. To fix, the whole dash has to be dropped so that the gates or doors can be accessed for repairs & the fan, it's half in & half out of the passenger compartment. I've had 3 or 4 dashes out to do this work but it is TIME CONSUMING. Wish you the best, GOD BLESS.....

- Check Voltage on pin 16 (BAT) and chassis (or body) ground. Always 12 Volts.
- Connect the Multimeter and check continuity between pin 4 (CG) and chassis ground. Less than 1 Ohms.
- Connect the Multimeter between pin 5 (SG) and chassis ground and check the continuity. Less than 1 Ohms.



- Check the fuse named OBD2 in the lower finish panel, under the dash on passenger side.


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- Check Voltage on pin 16 (BAT) and chassis (or body) ground. Always 12 Volts.
- Connect the Multimeter and check continuity between pin 4 (CG) and chassis ground. Less than 1 Ohms.
- Connect the Multimeter between pin 5 (SG) and chassis ground and check the continuity. Less than 1 Ohms.



- Check the fuse named OBD2 in the lower finish panel, under the dash on passenger side.


Thank you for visiting Fixya.

Hello: Go under the dash, passenger side. Remove under dash cover. Look straight ahead, you will see the blower motor with 2 wires. follow these wires to the blower motor model, on the module you will see a connector w/6 wires, these wires could be burnt, if so then the module may also be burned. You can get a repair harness at a GM dealer, You will have to splice it in. Make sure you line up the new connector wit the old so you get the wires in the proper order. If the module is burnt then you will have to replace it also. The blower motor is usually ok unless it is noisy or locked up. This is a common problem.

If your blower works at some speeds and not others, the likelihood of the blower motor needing to be replaced is low. The more common problems would be either the switch or the resister that regulates the motor speed. The resistor is usually located in the air duct under the dash.

If it only happens in cold weather, check your intake manifold bolts for tightness. #5 & #6 by the firewall are easiest to check. Some people will find these not even hand tight = rough running car.

However, if (when cold) your car is vibrating at idle IN GEAR and stopped, this would be a motor mount on Envoys and Trailblazer, very common.


Fan shouldn't turn by itself, you may have a bad fan clutch.

piece broken on fan blade of heater or it is warped. probably will have to replace unit.

check fan switch and fan motor as it sounds like the fan is causing the vibration,you need to look under the dash to get more info

That vibration is caused by something lying in the fan. This causes an imbalance in the fan that gives off the vibration. You will have to remove the blower motor in order to get to the fan and clear the fan of whatever is stuck in the fan.

needs a recircultion door, the stops break and the door is stuck between recirc. and fresh . the whole dash needs to come out. its about a 4and 1/2 hour job at the dealer. it can be done in less if you find a good tech. that is familiar.