heres my problem;
i got heat on the "windshield" setting but just warm heat on the "feet" setting, when im stuck in traffic i get more heat, when driving on the highway i feel cold air coming through the lower dash vents. All coolant hoses in the engine bay are hot. Rad cap is cold even after a long haul. I hear the vacuum lines on each setting.

i've changed:
heatercore
rad cap
thermostat is a cummins
full coolant flush

blender door is 1/4 closed
i got winter fronts on

im not sure what the problem is, ideas appreciated?

i've been told to check vacuum lines ill do that as soon as it warms up this week -16F is alittle too chilly.

 

There's been a few of these lately about heat issues.

I'm thinking an air lock in your heater core if everything else is operating properly.

Is your temp up to 190 on the gauge at normal operation?

 

no air lock in the syetem, the whole system was high pressure flushed at my mechanic, rads, block & heater core. Its slow to operating temp but it drop if i idle for more then 10mins

 

Joe, do you have the radiator blocked off? These things will do exactly what you describe, cool off while idling.

Also, are you sure the system is switching from defrost when you move the ****? Sounds stupid, but with a vacuum leak, it stays on Defrost no matter where the **** says.

 

ya i have the front grill covered.

yup im sure its switching when its on "defrost&feet" or upper vents cold air comes out of the vent. only setting it works on is defrost thats the only warm air i get, its warm not hot.

 

The blend door default position is defrost. Can you hear it swinging into place, or just the thump of activating the line?

Does it cycle airflow thru all of the settings?

 

the blender door work ok i tested it with the A/C it opens and closes ok.

all setting have airflow, defrost has warm air the others have cold air.

 

how long does it take to get up to temp?

was your evap core plugged up?

what brand heater core did you use?

also if slow to warm up, could be a faulty thermo right out of the box.

does the vent temp drop the higher the fan speed?

 

take about 20mins or 15kms going 100k on the highway, longer if in traffic.

ya alittle some crap came out.

cant remember off hand will have to check my records.

thermo is good its a cummins & i tested it by putting in a stant and it did the same thing.

ya at first but it warms up after a bit.


is there another vent door behind the dash? besides the blender door.

 

did you replace the sponge weather stripping around your heater core when you replaced it. I made that mistake in my 97. I took it all back apart and put the sponge seal around it and now i have lots of heat.

 

i'm getting warm air only in the defrost position so it is working its just not diverting air to the other heating positions

 

Mine has heat only if you turn on the a/c. It gets colder if you turn the fan switch to non a/c (makes no sense), but I have very low "output" from the vents. I have pulled the fan and cleaned out a bunch of leaves, but thinking about washing out the evap box?? I have very little heat / a/c while driving, I am running out of ideas.

 

remove fan and you can wash evap core off with low smelling brake cleaner. usually a huge build up of dirt/oil on core, typical symptom is low air flow

mine looked like this when I removed the heater box to replace leaking heater core

 

another "interesting" note is that when turning left i get a surge of heat.

i checked the vacuum lines in the engine bay and there ok.

 

so no one has had this type of problem?