Does your OBD control center operate? I say that so #1you can check for codes, and #2 test all the buttons to make sure they work in the DTC mode to eliminate the ECC control module "hi speed" button as culprit to your problem. Otherwise, it likely could be dirt on the power module connector if you're lucky. try to reseat it where it plugs into the motor there on your firewall. Otherwise you'd need to enter diagnostic mode, to isolate the cause of your problem, either the BCM or the Power module itself. There is a fuse too but since you are getting the low speed that is not your problem.
i cant find the control module, so probaly it is buit in the motor. the problem came after i disconnect the moter switch , after i reconnected it, i found the blower fuse burnt , so i put a new fuse, the blower begin to work but no high speed. very strange. if it is the blower, i can do nothing right?
thank you your help
Sadly, in one of their ingenious decisions, GM integrated the control module into the blower motor :hmm:. so it's pretty much unserviceable, unless you are a die hard DIY fix-it person, like myself. Rockauto.com sells them for a pretty penny(+- $200). Scrap yard time maybe?