My friend's 99 S-10 has a problem with things staying on when the key is off--like dash warning lights, and I believe also the blower and radio.

Any help is greatly appreciated.

 

I would check the door switches .See if they are plugged in and have power to them.That the switches are good and last the door panels have to be on the doors to work the switches

 

I just wanted to add this .That after turning the key to off and removing it. What ever door is opened first should turn off every thing Except the doom light.Which will stay on for a little bit after door is closed and then it will go out.

 

The warning lights, and blower should NOT be on when the key is off or taken out.

Radio is normal.
Power windows may also work.
But only until you open a door.

 

drperry ... my 2004 S-10 Owners Manual agrees with you ... I believe this feature has been available for several years.

Here is extract ...

Retained Accessory Power (RAP)

Your vehicle is equipped with a Retained Accessory Power (RAP) feature which will allow certain features of vehicle to continue to work for up to 20 minutes after the ignition key is turned to OFF.

Your radio, power windows, sunroof and overhead console will work when the ignition key is in RUN or ACCESSORY. Once the key is turned from RUN to OFF, these features will continue to work for up to 20 minutes or until a door is opened.

 

It's possible that the ignition switch has shifted or is hanging just going bad to.