No Heat
 

A friend of mine has a 2000 ctd and has very little heat? I haven't had a 2nd. gen in years and don't remember much. He changed the thermostat and coolant. Still the same. All the controls seem to be working properly. Is there a common problem with these? Any help would be great. Thanks!!!

How warm is it getting on the guage? Make sure all the air is out.

Yeah, make sure your guage is coming up to operating temp. I'd also look at your heater hoses back at the firewall. If you have an infrared thermometer with the little laser dot it's better, but if not do the touchy feelly thing. You want to see if the outlet is colder than the inlet. You inlet should be around, I don't know 140 degrees when your engine is at operating temp. I have seen a lot of heater cores stuck with dirt and crud causing low flow through the core and weak heat. How to fix, this may be easier than checking. I disconnect the hoses at the heater core, put a spare hose on the core itself and backflush the heater core to get any dirt and such out. Don't go crazy on the pressure from your water hose, just enough to flush the core. I'll do it for several minutes, usually just walk away and go talk or something. Then after that you can put your hoses back on.....that you marked and give it a try. If that did not work it could be something under the dash, maybe vacuum valve? I'm not to sure about these trucks, the cadillacs I worked on were all electronically actuated doors, but the trucks may have vacuum or electric.

I'd try flushing the heater core first then see what happens. Like I said, it's simple enough to try, don't cost anything. But feel the hoses and see if they even feel hot, they should be HOT, if they are just warm and you can lay your hand on there for a minute, you have a clogged heater core.

Good luck!!