Get the engine nice and hot and feel the coolant hoses going into the heater core from the engine bay, if both aren't the same temperature, then your heater core is clogged up, happens to mine at least every year.

 

Did you try replacing the thermostat?

 

Its been over one year since going back to the old style anti Freeze and system is still functioning good.

 

I had the same problem a while back, the heater would barely start to barely work after a long drive to work. It ended up being my thermostat was stuck open. Cheap and easy fix too.

 

I just fixed this on my truck and now the heat is insane...

The problem was the heater core was plugged up... Flushed out the heater core and all my issues were resolved...

Oh Yeah... Also make sure you have coolant in your truck... :P


ReDz

 

Did the Heater Core Back Flush and Coolant Flush and now the heat is working better then ever. Thanks for all your help everyone!

 

Figured out my issue. The "Blower Motor" is worn down. My uncle banged it (not too hard) and it came on. He said I can only bang it "on" for a couple times tho. it needs to be replaced. In the words of Homer Simpson: "Doh!"

 

check the anti freeze level. mine was low and at idle i wouldnt have heat. was half a gallon low

 

Having the same problem with a 98 blazer ,, I changed thermostat and flushed heater core but still blowing cold air , guess I'll flush whole coolant system and replace it with the green stuff.

 

Thanks for all the information. I took the easy way first and followed the lead of checking the hoses leading into the heater core. Low and behold the one was warm and the one closest to the drivers side cold. I removed the hoses and sprayed a garden hose into the heater core flushing it out until clear water ran and to my surprise the heat is flowing again. Now for the gas guage that seems to have an electrical issue and jumps from true reading to empty.