HVAC Blower Control Troubleshooting - JeepForum.com
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post #1 of 3 Old 11-11-2019, 07:52 PM Thread Starter
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HVAC Blower Control Troubleshooting

Hoping someone can help here.

2015 Wrangler JK, got wet in the rain. Blower and other HVAC are inoperative/intermittent.

The blower is under the glove box, and includes an integral controller and what looks like a removable monitoring module. The blower controller has a 3-wire plug which includes +12V/GND/CONTROL. Control is a small gauge wire originating in the HVAC control module in the center of the dash. Note that the fan control is continuous, and not the selector style from earlier models with the incumbent resistor.

The monitoring module has a small gauge 4- or 5- pin connector, and I'm guessing that it provides some sort of feedback.

Does anyone know the nature of the CONTROL signal? Guesses:

0-12 volts or a range in between
Maybe a pulse-width modulated signal

If we energize the +12V and ground ground, by the schematics that appears to "enable" the blower. When ground the CONTROL input we get a short burst of fan, thence nothing. +12V on the control input does nothing.

The schematics in the manual are helpful for interconnection, but provide zero in the way of real troubleshooting support.

Thoughts would be appreciated.

Last edited by coopermchaney; 11-11-2019 at 07:55 PM. Reason: Left something out
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post #2 of 3 Old 11-12-2019, 06:09 AM
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2014 JK Wrangler 
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I will try to help.

do you have MTC or ATC?
And I guess NO start stop?

Looks like a ATC - system
there are 2 wires on blower motor? DB dark blue is showing 12v KOEO? -

looks like module has 4 wires - I will need above info to go on - GTG

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #3 of 3 Old 11-14-2019, 07:09 PM
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Sorry for being a little late but here is some info

Both the ATC and MTC systems use a Pulse Width Modulated (PWM) circuit strategy. PWM voltage is applied to a comparator circuit which compares the PWM signal voltage to the blower motor feedback voltage. The resulting output drives the power module circuitry, which provides a linear output voltage to change or maintain the desired blower speed.

The blower motor power module is diagnosed using a scan tool

Both the Manual Temperature Control (MTC) heating-A/C system and the Automatic Temperature Control (ATC) heating-A/C system have an electronic blower motor power module to control blower motor speed. The power module uses a Pulse Width Modulated (PWM) input from the A/C-heater control and a feedback signal from the blower motor to regulate the blower motor ground path. On both systems, the blower motor receives battery current through the Totally Integrated Power Module (TIPM) whenever the ignition switch is in the Run position, and the blower motor control is in any position except off.

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