Guys,

I disconnected the negative battery terminal to reinstall new HID lights and after that the seat warmers and interior heater does not work. Did not touch anything electrical other than the battery and headlights. Would anyone know what has gone wrong with my 05 RX8?

 

Electronics 101, would tell you to check all your fuses and then go from there. Besides who uses seat warmers anyways???

 

+1
There is a 20A fuse labeled "seat warm"

 

The heater does not work at all with the **** turned to full heat. Any ideas how to diagnose this?

 

Did you check your fuses as we mentioned above?
Specifically, check the 7.5A A/C fuse since that energizes both the HEATER relay (for the blower) and the SEAT WARM relay (for the heated seats).

 

The thing is the AC blows really cold air but will not blow hot air if the **** is turned to the warm part. I have not had a chance to look at the fuses but which exactly are the ones I should be looking at if the heater and the heated seats are not working at all?

 

This isn't a difficult thing... check all the fuses!
It'll take you a couple minutes to do.

 

wow...

 

All the fuses are in good condition. The seat warmers do not work at all, and the heater only works now after I found out that you have to play with the temperature control **** to get it to the right setting by pressing down with pressure while turning to the temperature you want.

 

Check your HVAC controls ...

there is a DIY showing how to check it ...