Lets see. This is a 2006 model that has the known butyl patch leaking problem. I'm thinking that water has shorted the blower resistor somehow, grounded that circuit and allows the blower motor to run.
That's where I would take a look.

 

Like checking for loose connections, look for corrosion.

Seems plausible FMG, I didn’t think of that one.

 

A. the switch supplies ground through the resistors.
B. Batt + comes through the relay from the BCM fuse under hood.

Can't happen. That is if we are talking about the blower. Been some plum crazy problem descriptions lately though.

 

Ok so this might make a little sense but I’m still up in the air...and ironically, found an answer on here

 

When did you turn it on with a Tech2?

GoOgle tells me that "afterblow" is a dealer turn on option that is supposed to dry out the condenser to avoid stinky stuff growing. There is only a mention of it existing in the Service Manual, no other info. There is a TSB concerning it 99-01-39-004d; it hints that a shop might turn it on surreptitiously to avoid customer complaints in areas of very high humidity.

 

I bought this HHR Friday, I’m figuring stuff out with it as I go. But the fact remains that it kinda makes sense with what’s going on...

 

The HHR does not have the ability to turn on an afterblow in the control module. At one time GM offered a kit for certain vehicles that could be added but I don't remember the HHR as being one. The reference bulletin 99-01-39-004 does not exist in GM SI content but I did find this link. It last was 99-01-39-004i https://gm.oemdtc.com/4400/99-01-39-...ars-and-trucks

I did this to my Malibu the first week I owned it and it would come on almost exactly 30 minutes after I shut the vehicle off and had been driving with the A/C on. It runs about 30-60 seconds.

The OP stated it came on a few times and that would not happen with the afterblow being turned on. It runs one cycle and that's it.

 

Thank you for confirming what the after blow , meant to the HHR.