No heat and I think I've tried everything...

[jonrbrt]

I thought the same thing... simple... but I've actually given up on this. This is a repeat from earlier but I still cant believe I cant get this to work. The heater hose was hot on both sides of the heater control valve, but no heat so I decided what I thought was hot maybe wasnt enough so I by passed the heater control valve. still no heat! I removed hoses from heater core and simply used my garden hose to flush through. It appeared to me it was coming out as fast as it went in--so core is not plugged or restricted. Still no heat. I've had the inside duct work apart at the plastic "S" I can see the core and it feels hot. there is no mouse nest, no leaves... all flaps inside the truck move freely. While in the garage after the truck warms up I have heat it doesnt seem as hot as it should be but its warm air. As soon as the truck starts moving say 20 mph --no trace of heat. It must be a vent issue. I replaced the defrost last fall. but I have verified vents are working as they should and the routing on vacuum hoses is correct. The vent in the passenger kick panel never opens--it must be stuck closed--for winter that's good. I think it's the vent under the cowl---it seemed to be in the up position--and not moving. I unhooked it--I'm not sure it's closing all the way??? How does the cowl come off? Do you have to remove the fenders to get to screws on the sides? I'm thinking it may not be closing all the way. I can tell it's still attached to the linkage because I can move it but I can't tell and dont think it is going all the way down (towards the ground) I assume this would be the closed position.
Thanks for any ideas....

[Indyuke]

The vent door in the cowl won't have anything to do with getting heat. I doesn't hurt to fix it, but it's there to prevent hot air from coming in through the vents during the summer when you're running your A/C. It should only close when you have the A/C on.

[HuggerCST]

The cowl flap and kick panel vent are both controlled by vacuum and they control the fresh/recirculated air. If niether one are moving, then most likely they are not getting any vacuum. When the heat is on, the cowl flap closes, blocking out cold air, and the kick panel flap opens, allowing the fan to pull in heated air from inside the cab. So if neither one is working, you are trying to heat the colder, fresh air. That may not be your only problem, but it's definately part of it.

[HuggerCST]

Also, you can control the cowl flap manually, because the shaft comes through the firewall into the engine compartment where it connects to the vacuum pod.

[jonrbrt]

That's where I unhooked the vent under the cowl--in the engine bay. So I do want the passenger side kick panel vent open? How hot should the heater core be? I can touch the face of it from inside the cab while the duct work is apart. It's not so hot I can't hold my hand against it??? Shouldn't it be as hot as the radiator? Now the hose going into the heater core is almost too hot to hold onto--but coming out of the core I think I can hold onto the hose without fear of getting burnt--does the fan blowing through the core cool it that much? An even though my garden hose ran water through--could it still be restricted some how? I'm sure the core is not cluttered with leaves or trash simply because the fan blows air through it so strongly. I'm sure there must be a thread on removing the core in an AC truck.... I replaced my core about 15 years ago while I had the cab off the frame, but looking at it right now, I can't remember where to start.... I guess other than unhooking hoses from the firewall side--everything else comes apart from inside. The core is about the only thing I haven't replaced in the heating system.
Thanks

[Dark Knight]

Yep. The heater core is removed from the inside. Remove the hoses and four attaching nuts from the firewall side first. Then, the fiberglass box with the core in it should slide right out, with the removal of a few electrical connectors. It just might be the heater core. There's not much to a heating system. Hot coolant from the engine----> heater valve (vacuum operated)-----> heater core----> coolant flows back to the engine. Then there's the fan for air circulation of course. It's the only thing that you haven't by-passed or replaced. There could be some build-up inside of it...

[highperf4x4]

Dude, your heater core should fry your skin literally when it's hot. Your coolant is close to 200 degrees and your heater core should be the same. Imagine how fast the heater core needs to heat the air flowing through it with the fan on high even pulling fresh cold air from outside. It's got to be extremely hot. You either have a plugged heater core or you're simply not pushing enough coolant through it to keep it hot. Or your thermstat is stuck open and your coolant isn't getting hot enough. Or, you have your hoses routed wrong. Or, you've been abducted by aliens. It's just that simple!


I'm just sayin................

[Hottrucks]

you can pull your wipers off then the screws on the top and the ones under the rubber to remover the cowl.....then you can stick you hand in the cowl and feel the vent...open or closed...

if you want to check for crap against the heater core you can pull the engine side of the ac conderncer housing off the fire wall its kinda a pain but then you can slide the A/c condersor over and stick a vacum in there and get any poop out..I did mine this fall took me about an hour 1/2 to clean mine out....you'll also be able to see the falp in there and see if its working....if you look inside the cab behind the bend on the pass side you will see where the cable goes in..if you need I can get a pic for you ...it hard to see but its behind and down from where your A/C hose splits for the center dash vent..you can also feel it from the bottom ..hope this helps

[Hottrucks]

if this doesn't help we are going to talk on the phone and compare ..... I'll guide you though it....on a side note my cowl vent flap broke so I removed mine and my truck heats even when its 20*

just for ha has what does your engine temp guage read......I'm thinking you have a bad thermostat because when you move it cools so fast...a thermostat will regulate that...or a piece of cardboard in front of the radiator ..just watch your temp guage

[ryhan87]

Im having the same problem with my truck. However mine is not the A/C model. Does the non A/C model still use the whole vaccuum setup to control the fresh air door and water shut-off valve?

Here is and idea for your problem, if your gettin hot coolant in and out. I've seen heaters not perform to there best because of dust on all the fins of the heater core, blow out all the dust and it lets the heat transfer from the fins to air better. But by the sounds of it working fine in the shop but not on the road it almost sounds like its drawing air from outside rather than in the cab.

[swamp rat]

Originally Posted by jonrbrt

Heater hoses run from top of intake to core out core to water pump.

Which port on the water pump?? the one on the top (short wp) is pressure, the one on the passanger side is return for systems that don't have a radiator return.

[Dark Knight]

Whoa. A thread from the dead. Couple more days and it would have been a year old. My problem turned out to be a bad thermostat. It stuck open, so my engine never got hot enough to keep me warm.

['70_402]

Originally Posted by Dark Knight

Whoa. A thread from the dead. Couple more days and it would have been a year old.

i wonder if he ever got it working???

[Stocker]

Originally Posted by Dark Knight

Whoa. A thread from the dead. Couple more days and it would have been a year old.

Yup, and we never heard a final resolution from jonrbrt.

I wonder if he ever got his heat working -- and what the problem was?

I'm guessing restricted heater core....

[Dark Knight]

I don't know, but I sure would like to. It's almost like that thread (dare I bring it up?) from the General Discussion forum about the floor safe that was never opened. I'd pay handsomely to know what was in that safe. Unsolved mysteries bug me.