If you get no air out of the blower at all, then that may be easier / cheaper than a AC issue. Id start by checking fuses related to HVAC, followed by getting out a multimeter to see where you're losing signal (ie is the HVAC controller working, is there power at the fan motor, etc).

To driver 3's point- you noted the service was done - how recently? Was it fluid + filter or just fluid?

I'd also agree with driver 3's point that this service is unfortunately a fairly common one for places to sell and not do. Many people don't know what / how to check, and after another oil change worth of miles, there's no way to prove it one way or the other anymore. Certainly worth a look to pull out the trans dip stick and see what it looks like.

I'd still honestly prepare for the worst, especially at that mileage. There are several possible issues that can cause that problem - most of which would require at least partial trans disassembly. Of course no one would pull apart a trans with that much mileage and not rebuild the whole thing.

 

Tracy
check your coils first this can cause that and also the Cadillac converter.
if the check engine light is on in your car take it by O’Reilly‘s or a AutoZone and they can give you the code this will help a lot.
if it is the car they are very easy and less expensive to fix. (you have 3 of them but only one may be bad)

I have had the same problem with my blower staying on five and I did replace the blower in the car and I have also replaced the panel where all your switches are and it worked for a while but now it’s doing the same thing again.
however if I turn it to five and turn it back just a little bit it will start blowing correctly
Hope this helps you a little bit