96 S10 Heat always on

After searching the forum I am wondering on my 96 with manual temperature control, if the switch is bad or is the actuator bad? I turn the temp control to full cold and still have hot air?

Update: Needed to replace heater core anyway as I noticed some green drops on the floor mat, so I dropped the dash and split the box to replace the core. Noticed the blend door actuator was a real treat to get at! Finally pulled it and decided to pop the cover and sure enough, the white plastic gear was split in two. Went to index the blend door axle and it was locked up solid??? Now what %#@!&!!!! popped the heater core back out, removed the divider and the blend door was jambed up beyond the positive stop in the wide open position???? I convinced it to go back to normal position carfully and eveything was moving freely? Put everything back together and so far everything is working good.

Strange, maybe the rubber gasket wedged under the blendoor and allowed it to ride over the stop?

Thanks,
CSR44

It could be a problem with the rotary temp switch in the dash, the blend door actuator, the blend door itself binding, or wiring from the switch to the actuator.

See update in above.

Good piece of investigate surgery! Thanks for posting back with the fix!