Heat/AC interior controls

FREEBUS

MEMBER
1999 DODGE DURANGO
5.9L
V8
4WD
AUTOMATIC
174,000 MILES

My son and I changed the heater core in his vehicle listed above. After we replaced the dash the heater fan would not operate. We have vacuum to the interior vacuum control but no fan. Is there vacuum activated switch that powers the fan control? There is no off on the fan control.

3 Replies

JACOBANDNICKOLAS

MECHANIC
108,371 POSTS

The blower motor is electric and not controlled by vacuum. Did you reconnect the motor? The motor is located under the dash on the passenger side. The blower motor resister is under the hood on the firewall. I attached a pic of the motor. Check to make sure that is connected with an electrical connector.

Let me know.

Joe

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Monday, January 13th, 2020 AT 8:34 PM

FREEBUS

MEMBER
3 POSTS

The blower motor is connected but has no power. I know that the blower circuit is electrical but what activates the blower circuit. The only "off" is on the vacuum selector.

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Tuesday, January 14th, 2020 AT 12:10 AM

JACOBANDNICKOLAS

MECHANIC
108,371 POSTS

Hi,

I attached two pics. Let me know if that is what your control panel looks like. If it is, the top switch should be for the blower motor.

If you look at pics 3 and 4, they show the entire electrical circuit for the fan. Check the fuse and check for a ground. Pics 3 and 4 are overlapped so you can follow them.

As far as the blower motor, power is introduced from fuse 5 in the schematic. It then goes to the blower motor relay, to the blower motor, then through the blower motor resister, to the switch, and then the switch provides a path to ground. Once the switch is turned on, the ground completes the circuit and the blower motor should run. Speed is determine by which portion of the resister power passes through to the switch.

Let me know if that is what you needed.

Joe

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