I have a 2007 trailblazer and just recently started to have an odd vibration, like a horrible seat massage haha. Bascially what is happening is when I turn on the fan, while my car is in drive and stopped, it vibrates. If the AC is on, it vibrates, if the AC is off and just the fan is on, it vibrates. If the air circulation is set to circulate from in the suv, it vibrates but as soon as I turn the fan off, it stops. Or if the fan is on (not AC, just fan) and I turn it to circulate from the outside, no vibration. All other times, vibration.

I called an area shop and the owner said he used to own a trailblazer and knows exactly what I'm talking about and he was never able to figure it out before he gave up and sold it.

I did have the engine mounts replaced earlier this year. Though this started afterwards. About a month later this new issue came up. No change in idle when we are stopped, just vibrates. I really hope I explained it good enough. Its not the AC compresser cause it does this when the AC is turned off. Like I said, it does it with the AC on, with the AC off but just the fan on and with it doing the interior circulation. When the AC is on, it doesnt matter if its pulling air from the inside or outside. That only matters when its the fan only. And I only feel it when in drive and stopped at a stop light or stop sign type situation.

 

by fan you mean blower motor? if yes....remove the blower motor...rodents like to build nests in there and the build up w ith throw the blower motor fan out of balance.

 

When I look up blower motor, I have none of the symptoms of a bad blower moter that it lists. My only symptom is that awful vibration when the fan and/or AC is on and circulating air from in the suv. But your experience has pointed that vibration could also be blower motor? Does it have to be replaced usually or if something built a nest up there, a mechanic can just clean it out?

 

Done.