no heat?

[mike1589]

my heat stopped working completely recently, its kicked on once since then, but wont come on again, just blows cool air, ive replaced the thermostat, and the truck seems to be warming up fine and not overheating. any ideas what the problem could be? Maybe a bad fuse or relay? if so, which relay/fuse should I check, I read the manual and didnt even see one for the heater. Any help would be greatly appreciated.

[catlinB]

if you can hear the fan running , you could have a plugged heater core possibly???

[mike1589]

ya thats what I thought before but someone told me no way the trucks not old enough, its an 04, is it possible that the heater core could be plugged up?

[Dave]

Thermostats good?

Do you have a way to monitor ECT? The factory gauge isnt accurate at all. It reads normal at 100 degrees

Coolant tank full

[mike1589]

yup thermostats good, and coolant level is fine, im going by the stock guage, but the truck still warms up just as quick as it always did, and it doesnt overheat.

Also, like I said it did kick back on one time, and it was full blast, not just a little heat, so maybe im wrong but that seems like it would rule out a clogged heater core.

[Eddiy]

on the passinger side there is an inline heater controle valve above the valve cover i had the same problem replaced the vale and the heat worked great. allso cheke for louse or damage vac lines as its all vacume controled. hope this helpes

[mike1589]

ya that definitely helps, i see the valve your talking about, at least i thikn its the one, its right in the middle of the big rubber hose that goes into the heater core right?

[mike1589]

ok so i messed with that valve a little, heres what it does: i pull the vacuum line off, and it moves, not sure if it opens or closes, and i put the vacuum line back on, and it moves back. However, when i turn the knob from hot to cold in the truck, nothing happens, is it supposed to move when i do this? seems to me like the valve is not stuck, but maybe working incorrectly?

[Eddiy]

it controles the flow of antie-freez to the heater core. simple way to eliminate it as a possibal problem remove the valve and put a peace of pip in its place if u have heat after that then problem solved a new valve is 75 bucks i think.

[BirddogTN]

Your problem is probably the blend door actuator, located behind the glove box on top of the heater duct. It opens and closes the blend door (blends cold and/or hot air etc.) when you switch the control from cold to hot. There is a write up on how to replace it on the site somewhere. Try the google search function at the top of the page.