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I need some help diagnosing my heat problem please

Posted

When I turn my heat on it is just semi warm. I have searched the forum and checked everything. The Ac compressor kicks on and off correctly when the selector is turned. The air comes out of the appropriate vents when selected. The blend door works ( watched mopar video ) when the temp selector is turned. The big flapdoor over on the passenger side moves when the max AC is selected. The radiator was replaced and flushed 10,000 miles ago. New thermostat also. Temp gauge heats up to 190 and stays there no matter what I am doing. Both heater hoses going in from the engine side are the same temp and they are hot :evilgrin:. I pulled the glove box and can see and feel the heater core and the in and out pipes on it are both very very hot :evilgrin:. This heater use to get my truck unbelievably hot. I am inclined to believe its the heater core that is bad and I should just quit procrastinating and change it. Any thoughts would be appreciated.Thanks Rob

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They really work. The filter is as long as a 5 gal bucket. I all ready had the hole in the cowl because i knew it was just a matter af time until i found a scottys plus i tryed to make my own. I like the free air it grabs like the 70 ss chevelle.

  • 1 month later...

I have the same problem as the OP but I changed the heater core and I still don't get good heat like I use to. what I've done: changed heater core, flushed system, added cummins t-stat, replaced blend door motor shaft(wasn't broken),all 3 blend doors move(glovebox,2 under dash) Symptoms, now that its colder out, upon start up the windows fog up, the hot/cold regulator doesn't regulate so its either cold or hot no in between. water pump works well no leaks.so im at wits end! any input appreciated.

i have similar problems as you. biggest differance is i have not tried to repair anything yet. heat is either full on or full off, not as warm as it used to be either. i dont have the fogginh problem though. did you reindes the blend door motor when you repaired the shaft?

  • Owner
  JoeDiesel said:

I have the same problem as the OP but I changed the heater core and I still don't get good heat like I use to. what I've done: changed heater core, flushed system, added cummins t-stat, replaced blend door motor shaft(wasn't broken),all 3 blend doors move(glovebox,2 under dash) Symptoms, now that its colder out, upon start up the windows fog up, the hot/cold regulator doesn't regulate so its either cold or hot no in between. water pump works well no leaks. so im at wits end! any input appreciated.

  Quote

upon start up the windows fog up

That means there is another coolant leak in the HVAC box again.
  Quote

the hot/cold regulator doesn't regulate so its either cold or hot no in between.

Look down at the base of the HVAC case and check and see if the shaft is moving properly. You might have to take a jump over to Heater Treater and get a new bushing.
  Quote

replaced blend door motor shaft(wasn't broken),

Did you check the stepper motor for proper operation too? I know there is a rheostat strip in the stepper motor that controls positions it might be wore out... :shrug:

When I had an issue with my heat, I found that the stepper motor in the hvac box was my culprit. What happened was that the two contacts that provided power to the motor had broken off. 5 minutes later, and some solder, and it works as good as new now. Might check out your motor.

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    • Like 1
      Mopar1973Man said:

    That means there is another coolant leak in the HVAC box again. Look down at the base of the HVAC case and check and see if the shaft is moving properly. You might have to take a jump over to Heater Treater and get a new bushing. Did you check the stepper motor for proper operation too? I know there is a rheostat strip in the stepper motor that controls positions it might be wore out... :shrug:

    how do i check if theres a leak? i've replaced this already and it wasnt broken. this i didnt know, how do i check that? i also noticed that turning right i get a blast of hot air when the engine is up to temp.
    • Owner

    Passenger side of the trans hump is the stepper motor for the blend door... Turn the ignition to ON and not start the engine. Then turn the temp knob left to right and watch the shaft.

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    Welcome To Mopar1973Man.Com LLC

    We are privately owned, with access to a professional Diesel Mechanic, who can provide additional support for Dodge Ram Cummins Diesel vehicles. Many detailed information is FREE and available to read. However, in order to interact directly with our Diesel Mechanic, Michael, by phone, via zoom, or as the web-based option, Subscription Plans are offered that will enable these and other features.  Go to the Subscription Page and Select a desired plan. At any time you wish to cancel the Subscription, click Subscription Page, select the 'Cancel' button, and it will be canceled. For your convenience, all subscriptions are on auto-renewal.