Dodge P/U Heater Doesn't

randy427January 28, 2009

I suspect the heater control mechanism in my '96 Dakota P/U is not going into the recirc mode because the 'warmed' air coming out of the vents is about the same as the outside air.

Is there any way to put it into the recirc mode without a lot of disassembly?

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The heater system in your truck should be able to heat the air to around 140-160f, almost regardless of the outside air temperature. Recirculate will actually cause the windows to fog up more when cold, so by design, the heater, and defogger modes draw outside air. You will need to find out why the air is not being heated to fix your truck, the recirc door is not at fault whether it works or not.

    Bookmark   January 28, 2009 at 10:15AM
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Thanks for your quick reply.
What do you suggest I check first?
The heater hoses feel like there is proper flow through them.
BTW, it seems to heat up fine in warm weather.

    Bookmark   January 28, 2009 at 12:42PM
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What is your definision of " proper flow " ? A proper flow
means putting your entire hand on the heat side of the heater core hose and the return side and letting it sit there for about 3 seconds before your hand becomes burned.
That is after your motor is up to proper temperature. You
have a plugged heater core if your hand is not burned. If it heats up fine in warm weather your rad is also plugged.

    Bookmark   January 28, 2009 at 10:51PM
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"heats up ok in warmer weather"

Three things come to mind:

1. The actuators for the blend doors may be sticking or too stiff when very cold.

2. What kind of hot water control do you have to your heater core: Continous flow or flow only when heat is called for?

3. Engine thermostat not working

The continous flow type depends on good control of the blend doors to shunt the heater core out of the cabin air flow when no heat is wanted.

For switched hot water, the heater core is in the cabin inlet air flow at all times. Both heater hoses are connected to a diverter valve. This valve can be seen under the hood. When it is "off", hot water from the engine goes to the valve and is immediately returned to the return line thus not interupting the flow of engine coolant. When it is "on", hot fluid from the engine flows on the the heater core and then comes back through the return line.

This diverter valve may be operated by a vacuum acuator or a push/pull wire. Many use a vacuum actuator.

If you have a diverter valve, check it for proper operation.

If the engine thermostat is opening too soon or not shutting off when cool, you'll not have hot enough fluid through the heater core, and the engine will not come up to temperature in very cold weather, although I suspect that you would have noticed this.

    Bookmark   January 29, 2009 at 4:38PM
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It sounds like you've described the situation.
I believe I have the continuous flow variety as there are no control mechanisms on the heater hoses, both of which get hot when the engine is at temperature.
Would I have some access to free up or manually operate the blend doors without taking apart the dash? (If it matters, I also have A/C.)

    Bookmark   January 29, 2009 at 8:32PM
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