to start off the truck is a 2000 Ram 5.9
new thermostat (3 months ago)
new heater core (2 years installed by PO)
new Radiator (2 years installed by PO)
Blend door fixed and blend door motor replaced and working properly

the heat is just lukewarm during idle sometimes cold even but when i give it gas it gets warm (hot sometimes). now my first thought was bubble in the system and i have bleed the system and it is air free. I have even flushed the heater core out and it was free flowing. The odd part is when i feel the heater core it is very hot to the touch so it is doing its job even the bottom of the heating/AC box is hot where the heater core is. One question i have is when i have it set to the floor and vent setting i heard the A/C cycle is this correct ?????? and this morning i put my hand on the heater box and the heater core part was hot but i moved my hand over to where the evaporator is and it was ice cold and this is after the truck has been running for 40 mins. Any help on this would be great my dad has a 2001 and he is having a similar issue. The only other thing we have though of would be either the dash controls are going or the check valve is bad by the intake.

 

ok it looks like blend mode the a/c will be on according to the manual.

 

Either an air pocket or a blockage. Bleed it and then backflush the heater core.

 

that has already been done and like i said the heater core is very hot its just not getting through the vent hot.

 

On these trucks is the recirc door only closed on Full A/C?

 

Im having similar problems...

2000 Dodge Ram 1500 4X4 5.9l

I have multiple symptoms.

Symptom 1 - A/C Compressor runs no matter what setting(vent, floor, defrost, AC) the switch is set to.

Symptom 2 - Luke warm heat when set to 100% hot.

Symptom 3 - The faster I turn the fan up the colder the air coming out gets.


Known facts - New Thermostat, both hoses for heater core are very hot, heater core has been flushed, radiator/reserve is full, Actuator can be heard working when switching from cold to hot to cold, no problems with switching from floor to vent to defrost, recirc door behind glovebox is closed and nothing I do changes that.

Any ideas would be great because my mind is burned out on it.

 

If a 2000 is the same setup as my '98, pop off the glove box and check to make sure the blend door is opening all the way on full heat, you should be able to see the top end of the door rod. My cable clip came off my blend door rod last winter and I had NO heat unless I manually moved the door by way of the rod sticking out the bottom of the heater box with vice grips. The input hose should be hot and return should be cooler, your heat isn't getting out of the core.

 

My 95 did the same thing your talking about and it was the blend door not closing/opening all the way

 

well mine i think is fixed now, what i think it was is i had a pin hole on the top tube of the radiator and i mean pin hole i could smell antifreeze but until i got close i could see anything. it was just enough to leave a little residue of green. i ended up getting some AC Delco stop leak tabs and instead of putting all 5 in i put three because i hate putting foreign objects into my radiator. and then the next few days in the morning i would top off the system and park where the front end was higher than the rest of the truck and now i have really good heat. i still cant really put it on the highest setting but if i keep it on the second setting i have to turn it down on because i start sweating on my way home from work and i only work 12 miles from home. My theory is that the pin hole was sucking air and not letting it create pressure and not allowing it to push out the air in the system. Now i have to look at my dads 2000 ram he has zero heat.

 

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