2004 grand prix blower speeds

Hello,

Trying to get answer to problem on Daughter's car. 2004 Grand Prix, blower motor working fine, then suddenly will not work now except for level 5 setting. Nothing else, just wide open. Do not know whether to look at control unit or resistor/relay system. Have not had chance to check past posts, but appreciate any help anyone can provide me.

Blower motor resistor. Since high speed bypasses the resistor it will work even if the resistor is bad. Typically on a five speed setup there are four resistors. High speed is wide open so it does not need any resistance to slow it down. The other four resistors work in relation with each other to make up the other speeds. Low speed uses all four, the next higher speed uses 3, the next higher uses 2. and so on. The higher the speed the less resistance needed. Since only high works than the speed setting just below high is the one that is burned out, since the other lower speeds rely on that resistor.

For the '04 and up model Grand Prixs Pontiac redesigned the control circuits for the HVAC blower. The component is technically no longer called a blower motor resistor like found in the manual HVAC '97-'03 models. It is called a blower motor control module. ASIC and MOSFET components were added which are subject to transient voltage damage or high current conditions. Replacing the blower motor control module may not fix the issue since there appears to be continuing design issues and GM has a few TSBs out on it. Many members with '04 and up models that replaced the control module wound up with re-occuring problems or it did not fix the issue so that should be considered.

I would highly recommend checking older posts on this issue since the fix varies. If you cannot find any then let me know so I can reference you to them.

Would appreciate any info you could send my way, including locations of components, etc.

Thanks.

Autozone usually has a page showing the part location.