Where does the outside cabin air come from

DNALL53

MEMBER
2001 DODGE RAM
177,000 MILES

When my heater is in the heat position it blows cold air I can turn it off for a while and turn it back on and it will blow warm for about a min then starts blowing cold again blend doors are working heater hoses are hot on both sides cooliant is full and thermostat is working im confused.
thank you.

3 Replies

CADIEMAN

MECHANIC
3,544 POSTS

Recheck the blend doors. Your getting no cerculation through the core.

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Sunday, January 8th, 2012 AT 6:38 PM

DNALL53

MEMBER
1 POST

I was told there was two doors that worked the heater I found the one thats worked by the motor under the dash but cant find the other. And where is the outside air come in from because when I am setting still it gets hot in the cabin and starts getting cold when I start driveing.

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Sunday, January 8th, 2012 AT 6:44 PM

WRENCHTECH

MECHANIC
20,761 POSTS

With the engine at full operating temp, locate the 2 heater hoses where they go into the firewall and feel them to see if they are both hot to the touch. If not too hot to hold, then you have to look at the actual engine temp and if that is up, if it is, then your looking at a restricted heater core.
If you find that they are both too hot to hold, then the heat in that vehicle is controlled by a blend door that regulates heated air flow. It is operated by an electric motor/actuator. The problem can be that the actuator is stripped or inoperative or the door itself could be damaged. This is what needs to be determined by examining the actuator and see if it is responding to heat change commands or not.
If they are both not too hot to hold on to, then you either have a restricted heater core or the system is not completely full and getting air pockets for some reason.

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Sunday, January 8th, 2012 AT 6:50 PM