I only get heat when the control know is set to air conditioning.

1998 DODGE RAM
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LOWKEE
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i only get heat when the control know is set to air conditioning.
i have about 90 degrees of heat coming out of the vents. i have checked the doors and they are working properly. the thermostat was just replaced and is a 190 degree type.
i have back flushed the radiator but can not figure out why this is not giving the heat it should. someone said it might be a door actuator motor but where is this located and how to check it. please help its getting colder here in new york
Nov 7, 2010 at 12:39 PM
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JDL
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Does the engine reach normal operating temp? Are the heater hoses hot? The temp control uses a cable to operate door. With ac, no air comes through the heater core. With full heat, all the air comes through heater core. With the temp control in the middle, you get a mix. I'd have to locate temp cable and see if everything is working?


https://images.2carpros.com/forum/automotive_pictures/170934_97_ram_heater_1.jpg

Jun 23, 2021 at 9:38 AM
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LOWKEE
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i noticed today that when i am driving the air does not come out good. when i let off the gas the air comes out more. it leads me t believe a vaccum leak. but were do i start? and is there a way i could get that diagram? i could not save it
Jun 23, 2021 at 9:38 AM
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JDL
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Here is the vac diagram. My info shows that temp door is cable operated not vac. I don't have a better picture than the one posted.


https://images.2carpros.com/forum/automotive_pictures/170934_dodge_hvac_vacuum_1.jpg

Jun 23, 2021 at 9:38 AM
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LOWKEE
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is it possible that my new themostat is not working correctly and thats why i am not getting the right temp out?
Jun 23, 2021 at 9:38 AM
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JDL
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I asked if heater hoses were hot and if engine reached normal operating temp? I guess anything is possible as far as the thermostat?
Jun 23, 2021 at 9:38 AM
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LOWKEE
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yes the heater hoses are hot but i can hold them for a little while. but the temp gauges in the truck say about 150 degrees.
Jun 23, 2021 at 9:38 AM
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JDL
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If the temp gage is correct, that isn't hot enough.
Jun 23, 2021 at 9:38 AM
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LOWKEE
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okay. i will try another thermostat and let you know.
i also noticed that when you are accelerating the heater sounds like a door is opening or closing, but when you let off the gas the heater returns to a "normal" state.
Jun 23, 2021 at 9:38 AM
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LOWKEE
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i replaced the thermostat and still no difference. the temp gage is reading around 150 and the heater hoses and the heater core are hot to the touch.
Jun 23, 2021 at 9:38 AM
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JDL
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I'd verify the temp reading, using a non-contact thermomenter. Your probably going to have to check actuator doors, under the dash.
Jun 23, 2021 at 9:38 AM
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LOWKEE
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is there a way you can send me a better picture of the heater layout. its hard to see and i can not zoom it.
Jun 23, 2021 at 9:38 AM
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