Ok this problem just started, so heres whats up.. put in a new thermostat, 190degree.. my temp gauge on the adr. shows 190..dash shows the same, but when i'm driving all i get is luke warm air out the vents?? Now if i'm not moving and the pac brake is set it will blow hot? it has been around -20.. but i've had this truck 5 yrs and its my daily driver, and i've driven it at -30 with no problems, plenty of heat....like HOT.. now all the sudden i'm not gettin heat? Could this be a heater core problem or something else.. right now its -10 and i need heat!!! I do have a cold air cover on the grill, but as i said i've always had heat...any ideas would be great!! thanks

Capn

 

when was the last time the coolant was flushed?

i figured my heater core had gone bad earlier this year. so i picked one up along with all the fluids to drain, flush, then replace the cooling system fluids.

i drained and then ran the flush, and then replaced with new antifreeze. heat was significantly improved - so i thought heck ya - just wait till the heater core gets replaced!!!

i then replaced the heater core and i think i lost heat - because the new core had no foam around it to force the air thru the core itself, plus i think i sprung a small leak in the core when i replaced it.

my advice to you: go to cummins and get there flush (it's a yellowish liquid) and follow the directions on the bottle. then rinse it out with water and then replace the antifreeze to an appropriate ratio.

i realize it's cold out right now, and dealing with cold water outside would be less than ideal.

what i'm trying to get at: flush/clean the system prior to replacing the heater core.

 

Check your vacuum lines in the engine compartment to make sure something didn't get disconnected while you were under the hood.

 

Pay particular attention to the Pac's lines since it seems to work better with it engaged.
Leak could even be coming from the Pac's cylinder.

 

Ok heres an update.. dropped the glove box to take a look, that only shows the AC door, and its working properly! All my vaccum lines are ok, so after more research i'm seeing that the "blend door" on these trucks are prone to failing, actually the little plastic piece that goes on the motor to move the door! Has anyone had this problem, this would account for the colder it is outside the less heat i have comin out of my vents!! Now looking into this, looks like the whole dash has to be removed, anyone taken on that job? if your go to http://heatertreater.net/ you can look up this info... looks like a whole lot of work for a $10.00 part...grrr.. just wanted to know if anyone has had the dealer change this our or themselves..thanks Capn

PS..heater core is good, i have HOT lines in and out..

 

i think i got the same problem low heat, im gonna purge the system just incase theres air in the system if that doesnt work i'm gonna flush the heater core with CLR, change the thermostat & rad cap to start. I figure if that doesnt work ill have to tear into the heater core & replace it. But thanks Ed I didnt think of the vacuum lines i'll add that to my list.

 

CapnRam,

I have a very similar problem on my truck. I have no heat at all, and I pulled the dash half way off and checked the heater core lines and both were hot. I checked all the vacuum lines with no problems. I even checked the rheostat and it checked out good too. I found a diagram of the HVAC box that shows the servo that controls the blend door is on the passenger side under the dash almost resting on the trans hump. I managed to pull off the cover and to pull the motor and gears out of it (without removing the dash or HVAC box). I tried to turn the door manually with plyers and it wouldn't budge, leaving me with the impression that the blend door itself was stuck. I haven't dealt with it since, but I have heard that it cost about a grand to have this fixed because they have to pull the whole HVAC box out, which means you have to drain the engine coolant and freon.

Any idea how much the blend door servo mechanism cost?

 

Just looked at the link you posted above... that could very well be my problem. I'm just concerned since I couldn't move the blend door at all with a pair of plyers... Did you try moving the blend door yourself, if so were you able to move it any?

 

I did the broom stick trick and it worked really well. Lots of hot air now! I love it!!

 

What is the broom stick trick?

 

I found a post on here. You take your glove box door off and start your truck.
Turn the **** to max a/c and watch the blend door move. (its right behind your glove box door) Then turn it back to normal. After you see how it moves put it back to max a/c, then you take a piece of a wooden broom handle about 2 iches long and put it between the arm and the plastic housing. Then put it back to heat. The arm moves and captures the broomstick and this makes the blend door take more air from inside the cab.

I hope you can understand that.... Probably clear as mud!!
Do a search. Thats how I found it.

 

Do you mean the blend door or the recirculation door? I'll assume that you mean the recirculation door and not the blend door (turning to max A/C should not move the blend door, the blend door is controled only by the temp control ****).

I'm assuming what your saying is to compensate for the low heat output by forcing the system into a recirculation mode instead of allowing the air to be pulled from the outside and than heated, you allow the system to pull the air from inside the cab, where presumable the air is warmer there by allowing the system to work less with a lower temperature differential (most newer cars have this option with a recirculation button instead of a ****). That might help, but the problem is that the blend door is closed fully to A/C which bypas's the heater core completely. So forcing the system into a recirculation mode doesn't help any for my problem.

I have searched this forum intently several times trying to find a solution to the issue with my truck with no luck. Thanks for the input, it's a good idea that may come in handy if I'm ever able to get the blend door to move...

Brad

 

That sounds to me like thats the "recirc" door it closes to block outside air from entering the heater plenum. By jamming the door to the recirc position it will only take air from inside the truck causing problems with fogging windows.

The blend door actuator is on the passenger side right by the hump, it's electric and connected to the blend door shaft.

I would ensure that the rad is totally full and no air in the heater core. If the blend door won't move with the actuator removed then when you replaced the heater core you did not ensure that the blend door shaft was located in the pivot holes top and bottom correctly. To fix this requires heater plenum removal and disassembly to locate the door correctly. SORRY

 

Disregard the comments about the blend door. When I scrolled up to re read the OP I read post number 2 that said the heater core had been replaced.

 

It looked to me that the motor screw toward the fire wall couldnt be gotten to, my carpet covers it up, so i'll look into this more, not forsure if you would be able to move the door by hand since its hooked up to that motor?? THis has got to be the problem!!! I ordered the part from heatertreater yesterday so i'll plan this job for next weekend!! i'll keep ya posted..and the part was $30.00 with shipping...

Capn