i have a 1999 gmc burb. all leather/ power dual climate runs great and has for the 14 years ive had it but never heats up. Sounds like a dream right. at any given time i can grab the hose and its warm not hot. my a/c works great because of this but the heater takes forever to heat up suck a large space. i have had this burb since it had 30ish miles on it and now 215k. never cared about heat before but i have kids now. can anyone explain this to me.

 

Where does the temperature gauge level out after you've been driving it for 10-20 minutes?

My first guess would be a bad thermostat. If it's stuck open, the engine would never get up to normal operating temps. That's an easy $20 fix.

 

after 20 mins the gauge is still at the first marker. after about an hour its its up to the 2nd. in a pan of water the thermostat opens at 178 degrees. Some times i can squeeze the hose and its hard cause T stat is closed and sometimes its soft cause its open. i have been a mechanic for 20 years but this one has me stumped. Its not a big deal cause the burb runs great and has never overheated even in the 100+ temps in oklahoma. This pic is after an hour sitting in gear with ebrake on at an idle.

 

Temperature sensor?