I have a 2004 chevy trail blazer it wont heat very well only luke warm air I have changed the fan thermostat and water pump

if you used some rad sealer the thermostat is probably bad, so it will be overheating, this will blow the head gasket. take the thermostat out and refit. without the it in, go for a drive, the temp should rise up and down. when you come back leave to cool down. and flush the system out with fresh water, and then replace with new thermostat, if no leaks top up with antifreeze and water, leave top off and run engine to get bubbles out of engine squeeze radiator pipes as warming up. and top up water as it goes below line. when all air is out and fan has come on to say its at full temp. leave to go cold. and top up if needed and put cap back on.

A number of things including a stuck thermostat, low coolant, or a faulty water pump.

are you talking about your heater core for heat in the truck ? is there a valve in the heater hose that you have to open to get the hoses hot to the core this is under the hood , follow the hoses , could be clogged core , does it over heat , or get up to temp should be about 190 normal temp for most motors why did you change these parts anyhow , did you use the radiator fix bars leak stuff that you put in , bars leak , if so you may have clogged your core , take the hoses off the core and blow it out ,pain in the but you went this far , ck for that valve to open

It's not a pump problem. Check the thermostat and coolant flow through the heater itself.

While it doesn't seem likely, if you've changed, or had the thermostat changed.... I'd say you got a faulty thermostat. I am curious as to what your temperature gauge says the temperature of the engine and coolant is.. If your gauge is showing hot, I can think of two more possibilities... the water pump isn't pumping right... and, if the water pump isn't working right, the problem can be a cracked head or block, which can cause an airlock in the coolant system. Check the coolant or radiator cap.

your gonna have to remove actuator and manually move door to see it that helps.
did you get right actuator? there are 2, 1 manual and 1 auto climate controls. maybe reduce file size or change format? Take a look
www.xcardiag.com

May check to make sure that the hose is not being obstructed. What temp does the engine usually get to?

Thermostat is not working. Replace it and you should have hot/warm like it used to.

you have a bad/stuck/ wrong thermostat

You may have vapour lock in your heater lines. Start engine, put heat lever on high, disconnect one of the lines on your heater core, the one on the flow out side, & see if you have any air coming out. Once antifreese comes out stick line back on & retighten clamp. Make sure your cooling system is topped off. Also your water pump may not be functionihg to it's maximum. Take rad cap off cold & view flow rate. If inadequate you may have to replace the water pump. Good luck!