[Jbuchy]

Hi, I have a 2012 RAM 3500 6.7 that has poor heat. We have been fighting with this well over a year now. This is what we have done: Replaced heater core. Complete cooling system chemical flush, twice. New 200 degree thermostat. New fan. Checked all blend and mode doors for proper movement. Checked recirculating door.
Engine temperature is good. This truck used to have excellent heat but about 2 years ago started going down hill. It's warm but not hot like it used to be. I have tried everything I have read in these forums with little improvement. We are at a loss of what to do next.
Thank you all in advance.

 

[Handy1]

This is is not specific to our Ram trucks. The auto industry used to use a valve in the heater hose that would close when the heater is off and the AC is on. I don’t know if this valve is still used or not. If it is used ,and yours is stuck closed or mostly closed,then your heater core would never get hot,it would only get slightly warm. I have also seen water pumps that would be worn and not provide enough water flow to keep the heater core hot. Again this is not specific to the Ram truck. Just problems I have run across in the past. My son has a Jeep Liberty. The heater core in it plugged off. They are made with a common rail. Water can flow through the rail and not actually get into the cores themselves. So if the core gets plugged,the water will flow right through it and return back. I don’t know if the Ram is made that way or not,but you replaced the core,so that would elemenate that.

 

[6.7L_MegaCab]

I'd look into your hvac controls on your center dash. Perhaps the cool/heat controls aren't functioning as they should.

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[Jbuchy]

This is is not specific to our Ram trucks. The auto industry used to use a valve in the heater hose that would close when the heater is off and the AC is on. I don’t know if this valve is still used or not. If it is used ,and yours is stuck closed or mostly closed,then your heater core would never get hot,it would only get slightly warm. I have also seen water pumps that would be worn and not provide enough water flow to keep the heater core hot. Again this is not specific to the Ram truck. Just problems I have run across in the past. My son has a Jeep Liberty. The heater core in it plugged off. They are made with a common rail. Water can flow through the rail and not actually get into the cores themselves. So if the core gets plugged,the water will flow right through it and return back. I don’t know if the Ram is made that way or not,but you replaced the core,so that would elemenate that.

Thanks for your reply. I know what valve you are referring to, I have seen them before but there is no such valve on this truck. The water pump is the only thing I haven't tried. I figured that it would probably overheat if the pump was that bad. Maybe I'm wrong.

 

[Jbuchy]

I'd look into your hvac controls on your center dash. Perhaps the cool/heat controls aren't functioning as they should.

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We looked at that too. All doors are moving freely and are moving into the proper positions.

 

[6.7L_MegaCab]

It's not whether or not the doors moving but whether the temperature control affects the temperature change.
Check out the procedures below:

Do you have a Laramie with Automatic Dual Zone controls or Manual Single Zone Controls (with the 3 knobs)?

24 - Heating and Air Conditioning / Diagnosis and Testing

HEATER PERFORMANCE
Before performing the following tests, see Group 7 - Cooling for the procedures to check the engine coolant level and flow, engine coolant reserve/recovery system operation, accessory drive belt condition and tension, radiator air flow and the fan drive operation. Using a scan tool, check for any Diagnostic Trouble Codes (DTCs) in the A/C-heater control, Totally Integrated Power Module (TIPM), Powertrain Control Module (PCM) or Engine Control Module (ECM), depending on engine application. Repair as necessary (Refer to 28 - DTC-Based Diagnostics/HVAC - Diagnosis and Testing).

MAXIMUM HEATER OUTPUT: TEST AND ACTION
Engine coolant is provided to the heater system through two heater hoses. With the engine idling at normal operating temperature, set the temperature control to maximum heat position, the mode control to the floor position, and the blower motor control to the highest speed position. Using a test thermometer, check the temperature of the air being discharged from the floor outlets. Compare the test thermometer reading to the Heater Temperature Reference chart.

OBSTRUCTED COOLANT FLOW
Possible locations or causes of obstructed coolant flow are as follows:

1. Inoperative water pump.
2. Inoperative thermostat.
3. Pinched or kinked heater hoses.
4. Improper heater hose routing.
5. Plugged heater hoses or supply and return ports at the cooling system connections.
6. Plugged heater core.

If proper coolant flow through the cooling system is verified, and heater outlet air temperature is low, a mechanical problem may exist.

MECHANICAL PROBLEMS
Possible locations or causes of insufficient heat due to mechanical problems are as follows:

1. Obstructed cowl air intake.
2. Obstructed heater system outlets.
3. Blend-air door(s) or actuator(s) not functioning properly.
4. Faulty blower motor system
5. Inoperative A/C-heater control

TEMPERATURE CONTROL
If the heater outlet air temperature cannot be adjusted with the temperature control on the A/C-heater control, the following could require service:

1. Inoperative A/C-heater control.
2. Inoperative blend door actuator(s).
3. Inoperative, obstructed or improperly installed blend-air door.
4. Inoperative related wiring harness or connectors.
5. Improper engine coolant temperature.

 

[Jbuchy]

It's not whether or not the doors moving but whether the temperature control affects the temperature change.
Check out the procedures below:

Do you have a Laramie with Automatic Dual Zone controls or Manual Single Zone Controls (with the 3 knobs)?

24 - Heating and Air Conditioning / Diagnosis and Testing

HEATER PERFORMANCE
Before performing the following tests, see Group 7 - Cooling for the procedures to check the engine coolant level and flow, engine coolant reserve/recovery system operation, accessory drive belt condition and tension, radiator air flow and the fan drive operation. Using a scan tool, check for any Diagnostic Trouble Codes (DTCs) in the A/C-heater control, Totally Integrated Power Module (TIPM), Powertrain Control Module (PCM) or Engine Control Module (ECM), depending on engine application. Repair as necessary (Refer to 28 - DTC-Based Diagnostics/HVAC - Diagnosis and Testing).

MAXIMUM HEATER OUTPUT: TEST AND ACTION
Engine coolant is provided to the heater system through two heater hoses. With the engine idling at normal operating temperature, set the temperature control to maximum heat position, the mode control to the floor position, and the blower motor control to the highest speed position. Using a test thermometer, check the temperature of the air being discharged from the floor outlets. Compare the test thermometer reading to the Heater Temperature Reference chart.

View attachment 916650

OBSTRUCTED COOLANT FLOW
Possible locations or causes of obstructed coolant flow are as follows:

1. Inoperative water pump.
2. Inoperative thermostat.
3. Pinched or kinked heater hoses.
4. Improper heater hose routing.
5. Plugged heater hoses or supply and return ports at the cooling system connections.
6. Plugged heater core.

If proper coolant flow through the cooling system is verified, and heater outlet air temperature is low, a mechanical problem may exist.

MECHANICAL PROBLEMS
Possible locations or causes of insufficient heat due to mechanical problems are as follows:

1. Obstructed cowl air intake.
2. Obstructed heater system outlets.
3. Blend-air door(s) or actuator(s) not functioning properly.
4. Faulty blower motor system
5. Inoperative A/C-heater control

TEMPERATURE CONTROL
If the heater outlet air temperature cannot be adjusted with the temperature control on the A/C-heater control, the following could require service:

1. Inoperative A/C-heater control.
2. Inoperative blend door actuator(s).
3. Inoperative, obstructed or improperly installed blend-air door.
4. Inoperative related wiring harness or connectors.
5. Improper engine coolant temperature.

This truck is loaded with dual zone climate control. The temperature issue affects both driver and passenger. Could it be the water pump?

 

[Loki223]

This truck is loaded with dual zone climate control. The temperature issue affects both driver and passenger. Could it be the water pump?

What does your engine coolant temperature read at? i doubt the water pump would be at fault if it's been an issue for over a year, but if your truck never reaches operating temperature, there would be a chance that the thermostat got stuck open. The cooling system on these trucks is very robust, so if the thermostat were to stay open, there is a good chance you would never get to temp unless you were loaded.

 

[Jbuchy]

What does your engine coolant temperature read at? i doubt the water pump would be at fault if it's been an issue for over a year, but if your truck never reaches operating temperature, there would be a chance that the thermostat got stuck open. The cooling system on these trucks is very robust, so if the thermostat were to stay open, there is a good chance you would never get to temp unless you were loaded.

The gauge will go up to 100 C. The thermostat was replaced at the beginng of all this but I took it out to check. It is not stuck open.

 

[Loki223]

Do you have an IR temperature gun to measure coolant hose temps going to the heater core?

 

[6.7L_MegaCab]

I doubt it's the water pump if your coolant temp stays around 200 deg F and doesn't have a problem getting to temp.

Sounds like to me you might have an inoperative
A/C-Heater control since you are unable to adjust the temperature to your desired setting and that is the only thing you haven't changed. These do go bad. Rare, but they do.

There is also an IR temperature sensor in the truck that measures body temperature. Perhaps that is not reading correctly. Doubtful though.

I would first make sure you have got 100% of the air out of the engine cooling system using the cooling system bleed screw. This might require the use of a vacuum, especially since you changed the heater core. Personally I would start the truck and get it to temp then crack the coolant bleed port until coolant comes out with zero indications of air.

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[6.7L_MegaCab]

Did you get the heater control resolved?

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[Les w/2013 3500]

Did you get the heater control resolved?

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Have a similar issue with my 2013 Laramie 6.7l with dual zone climate control. No related error codes from a scan. Virtually no heat in cab even with engine at proper operating temperature. IR gun says heater inlet and outlet hoses are hot too, (about 10 degrees cooler than engine temperature). So I'm thinking either the heater core is plugged and coolant is bypassing or the blend doors are fouled. But how to tell? Would flushing and cleaning the whole cooling system unplug a heater core? A cheaper place to start. Is there a routine to re calibrate the actuators in the climate control system. Any comments would be helpful.

 

[Sclifton78]

Have a similar issue with my 2013 Laramie 6.7l with dual zone climate control. No related error codes from a scan. Virtually no heat in cab even with engine at proper operating temperature. IR gun says heater inlet and outlet hoses are hot too, (about 10 degrees cooler than engine temperature). So I'm thinking either the heater core is plugged and coolant is bypassing or the blend doors are fouled. But how to tell? Would flushing and cleaning the whole cooling system unplug a heater core? A cheaper place to start. Is there a routine to re calibrate the actuators in the climate control system. Any comments would be helpful.

I had the same issue. I replaced the heater core and evaporator core, all the actuators, put all new aluminum blend doors from blend door USA, it already has a new water pump & thermostat, vacum bleed the coolant and still barely got warm heat. Come to find out in the air box for blend door for the heater it's a little worn and let's the door have play and it snags on the air box and doesn't open completely. I found that by checking how much the actuator turns compared to how much I could turn the door by hand. It was only opening half way. If I jiggled it it would pop past the housing and BAM heat. I am assuming I'm going to have to pull the airbox again and figure out how to fix that issue. At least now i know though. Been banging my head on the wall for 2 yrs over that.

 

[Les w/2013 3500]

Wow. I hope mine is an easier fix. When I posted the first I didn't realize my scanner does not read HVAC codes. Taking it to the dealer Tuesday to have them scan the HVAC. If it is a blend door issue hoping then can calibrate the actuators. Probably a long shot. Since I posted I now of have some heat on the passenger side but none on the driver's side. In another form someone with that issue said a heater core back wash helped as driver and passenger heat comes separate halves of the heater core (dual zone). He believed the driver side of the heater core was plugged. If dealer scan shows blenders are working properly I will try the core back wash. Will either have to wait for spring or have the dealer do it as it is -12C (10F) here this morning and I don;t have water in my shop. Will post dealer scan results.

 

[Thatnewguy]

Following. Have a similar issue with my 2011, heat is hot but doesn't blow hard enough to heat the cab.

 

[Les w/2013 3500]

HVAC scan at the dealer did not turn any actuator faults so went ahead and had them back wash the heater core. Now there is heat on the driver side although not as warm as the passenger side. I am guessing that this is not a permanent fix and the heater core will have to be replaced, eventually. Outside temperatures are drifting towards is for -24C (-11F) by Christmas. Happy to have some heat.

Following. Have a similar issue with my 2011, heat is hot but doesn't blow hard enough to heat the cab.

I'm no expert but would suggest either the fan is malfunctioning or you actuators that are not functioning as they should and not allowing warm air to flow. A dealer HVAC scan could reveal the problem. It cost me $90 Cdn to have get the scan.

 

[Thatnewguy]

I'm no expert but would suggest either the fan is malfunctioning or you actuators that are not functioning as they should and not allowing warm air to flow. A dealer HVAC scan could reveal the problem. It cost me $90 Cdn to have get the scan.

I suppose ill have to take it in, was hoping it was something simple but after digging some more on the site that doesnt seem to be the case.

 

[Smiley3303]

Add me to the mystery. 2014 Cummins.

 

[joshdice13]

This truck is loaded with dual zone climate control. The temperature issue affects both driver and passenger. Could it be the water pump?

jbunchy Did you ever figure out the no heat problem? if so.. myemail is [email protected] im having the same problems