I have a 1999 dodge ram 1500 sport quad can 5.2. 4x4. I haven't had any heat for awhile , found out my heater core was leaking, so I replaced that , while in the dash I replaced my temp. Control acuator and I still don't have any heat. The thermostat was just replaced a few months ago and all collant levels are high. Once the truck warms up. I touch the heater core hoses and both are hot. What else is there left to replace ? Possibly the actuall control unit on the dash ?

 

When you replaced the heater core did you make sure the interior blend doors were in the correct positions before putting the box back together? I assume you have the electric motor for the one door. Get a flashlight and a friend. look under at the motor while the friend turns the control to hot and cold. You should see it turn a good distance both ways. If it only turns an 1/8" or so, the door is not on the correct side.

 

It seems very likely you have a broken blend door, it's a common problem. Checkout heatertreater.net for diagnosis and the kit solution.

 

Hi,
i live in sunny So. Cal where the heat is relentless and dries everything out.

here is what i got...

01 1500 laramie slt....BRAND NEW HEATER CORE. 2 months old on that part. heat was working fine for this chilly morning....i noticed a burnt smell and knew it was coolant. I find the intake hose for the heater core has busted right where clamp is on the valve cover. i get 9' of 5/8" (6.50)and replace it after work (I work at O'reilly's).

Yes, i was too lazy to replace heater hose when core was done...serves me right.

now, new heater core, new heater hose and clamps, and i turn truck over to burp and fill.

heat on and blower on full...truck is warm. pure a/c air is coming out.

heat was working fine this morning with hose busted....i know it had nothing to do with the interior side, I must have knocked a vacuum hose loose. i trace all hosing on right (pass) side near firewall, no cracking, but tubing is hard. track back to in front of engine and down under the battery. I find the connecting and BAM. cracked vacuum tubing at the servo motor. I will replace and get back to you guys about this one...should be only vacuum tubing causing the pure a/c on heat setting (blend door not working, vacuum problem)

 

Blend door isn't vacuum powered, on yours, there is a servomotor on the bottom of the heater box that operates it.

 

what accounts for the two (smaller than 1/8") tubing lines that goes into the firewall on the passenger side? and the multiple vacuum connections behind the thermo **** (climate control) assembly? it may very well be a motor but i believe on the 2001 model i have, a motor down there swinging the blend door will be actuated by vacuum and that vacuum is split to pull double duty on the cruise control line too.

why is a tsb solution of the vacuum check valve installed on a line against the firewall to fix a blend door problem?

side note:

going back to work last night, i found nothing equal in diameter to this tubing....i bought some 1/8" and 3/64" tubing, i will have to rig something together for these two to work. i also will use my assrtd vacuum connectors to find a solution to this...as of now the vacuum line that works in tandem with the cruise control is my suspect. will have to tap resources to find replacement fix. for now, i will try and swing the door to heat for the time being, and work on a solution by night...initial problem of heater hose is fixed, and about to re-do the front brakes right now, will come back to the heater soon.

 

The TSB is to fix wild vents. Where the air comes out, not what temp it is. Blend door is purely electrically powered (temp), where the air comes out is purely vacuum powered.

 

UPDATE ON VACUUM LINES for heating problem...

i came up with a solution of keeping the existing vacuum lines (inspected the full run of them for more cracking, none) and used the 3/64 rubberized hosing as coupler material....just jammed the 1/8" tubing into the 3/64, snug fit and no leaking.

fixed it, then had to jerry rigg a 1/8 vacuum connector to go into the check valve and sealed that.

now the heater is back to blowing heat, not refrigerated air. and the vents are coming out the right vents.

in recap: i replaced the 5/8" heater hosing, fixed cracked vacuum lines (hard tubing) for hvac and crusie control servo/units.....and all is back to normal. nothing else was worked on in the interior and just replaced and fixed vacuum lines.