Strange HVAC problem
Thread Starter
Safety Car
Joined: Mar 2007
Posts: 3,518
Likes: 37
Strange HVAC problem
When the car is on and the HVAC is on it works fine as it should. When the HVAC is turned off it has the blower at full blast.
Blower is at full blast even with the car off and also even with the key out of the car.
Battery off so it doesn't drain.
Anyone know what it is?
Blower is at full blast even with the car off and also even with the key out of the car.
Battery off so it doesn't drain.
Anyone know what it is?
Pro
Joined: Sep 2007
Posts: 735
Likes: 7
From: Bucks County Pa
AC Blower always on
Hi, you've most likely got a short to ground. The blower housing is hot all the time. If it's grounded it will run the blower even with the key off. the short may be in the blower control processor, (if automatic temp dual zone ), or blower motor resistor assembly,(if manual 3 **** unit), the wiring, connectors, or any place in the circuit. The best way to start is to access the blower motor, and visually look for any possible wire or grounding source touching the case. If there is none, the most likely next cause is the blower motor control processor, or resistor assembly. If thats not the problem, there is a short in the circuit somewhere where wires have possibly been rubbed through, or a connector has burned through etc.
Good Luck
See below for a diagnostic to help you find it.
++++++++++++++++++++++++++++++++++
Blower Motor Always On
Step
Action
Values
Yes
No
Schematic Reference: HVAC Schematics
Connector End View Reference: HVAC Connector End Views
DEFINITION: The blower motor is ON while the HVAC control is in the OFF position.
1
Did you perform the HVAC Diagnostic System Check?
--
Go to Step 2
Go to Diagnostic System Check - HVAC Systems - Automatic
2
Turn ON the ignition, with the engine OFF.
Turn OFF the HVAC controls.
Is the blower motor OFF?
--
Go to Testing for Intermittent and Poor Connections in Wiring Systems
Go to Step 3
3
With the scan tool observe the Desired Blower Mtr Speed parameter in the Heating and Air Conditioning data list.
Does the scan tool indicate that the Desired Blower Mtr Speed parameter is near the specified value?
0 counts
Go to Step 4
Go to Step 7
4
Disconnect the HVAC control module.
Does the blower motor continue to operate?
--
Go to Step 5
Go to Step 7
5
Inspect or test the blower motor housing and the blower motor control circuit in the blower motor harness for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 10
Go to Step 6
6
Inspect for poor connections at the harness connector of the blower motor control processor. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 10
Go to Step 8
7
Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 10
Go to Step 9
8
Replace the blower motor control processor. Refer to Blower Motor Control Processor Replacement .
Did you complete the replacement?
--
Go to Step 10
--
9
Important
Perform the recalibration procedure for the HVAC control module.
Replace the HVAC control module. Refer to HVAC Control Module Replacement .
Did you complete the replacement?
--
Go to Step 10
--
10
Operate the system in order to verify the repair.
Did you correct the condition?
--
System OK
Go to Step 3
Good Luck
See below for a diagnostic to help you find it.
++++++++++++++++++++++++++++++++++
Blower Motor Always On
Step
Action
Values
Yes
No
Schematic Reference: HVAC Schematics
Connector End View Reference: HVAC Connector End Views
DEFINITION: The blower motor is ON while the HVAC control is in the OFF position.
1
Did you perform the HVAC Diagnostic System Check?
--
Go to Step 2
Go to Diagnostic System Check - HVAC Systems - Automatic
2
Turn ON the ignition, with the engine OFF.
Turn OFF the HVAC controls.
Is the blower motor OFF?
--
Go to Testing for Intermittent and Poor Connections in Wiring Systems
Go to Step 3
3
With the scan tool observe the Desired Blower Mtr Speed parameter in the Heating and Air Conditioning data list.
Does the scan tool indicate that the Desired Blower Mtr Speed parameter is near the specified value?
0 counts
Go to Step 4
Go to Step 7
4
Disconnect the HVAC control module.
Does the blower motor continue to operate?
--
Go to Step 5
Go to Step 7
5
Inspect or test the blower motor housing and the blower motor control circuit in the blower motor harness for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 10
Go to Step 6
6
Inspect for poor connections at the harness connector of the blower motor control processor. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 10
Go to Step 8
7
Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 10
Go to Step 9
8
Replace the blower motor control processor. Refer to Blower Motor Control Processor Replacement .
Did you complete the replacement?
--
Go to Step 10
--
9
Important
Perform the recalibration procedure for the HVAC control module.
Replace the HVAC control module. Refer to HVAC Control Module Replacement .
Did you complete the replacement?
--
Go to Step 10
--
10
Operate the system in order to verify the repair.
Did you correct the condition?
--
System OK
Go to Step 3
Thread Starter
Safety Car
Joined: Mar 2007
Posts: 3,518
Likes: 37
First I want to say this is a great forum. People helping with things, etc.. makes this a much better experience with the car.
That isn't said often but is implied often by lots of people.
Next, For this problem, I removed the dual zone HVAC control and the blower continues to blow full speed even with the key off. Need to do the following per the write up next:
"Inspect or test the blower motor housing and the blower motor control circuit in the blower motor harness for a short to ground."
How do I get to the blower motor and blower motor harness?
Thanks!
That isn't said often but is implied often by lots of people.
Next, For this problem, I removed the dual zone HVAC control and the blower continues to blow full speed even with the key off. Need to do the following per the write up next:
"Inspect or test the blower motor housing and the blower motor control circuit in the blower motor harness for a short to ground."
How do I get to the blower motor and blower motor harness?
Thanks!
Burning Brakes
Joined: Aug 2006
Posts: 1,217
Likes: 5
From: Stark County Ohio
First I want to say this is a great forum. People helping with things, etc.. makes this a much better experience with the car.
That isn't said often but is implied often by lots of people.
Next, For this problem, I removed the dual zone HVAC control and the blower continues to blow full speed even with the key off. Need to do the following per the write up next:
"Inspect or test the blower motor housing and the blower motor control circuit in the blower motor harness for a short to ground."
How do I get to the blower motor and blower motor harness?
Thanks!
That isn't said often but is implied often by lots of people.
Next, For this problem, I removed the dual zone HVAC control and the blower continues to blow full speed even with the key off. Need to do the following per the write up next:
"Inspect or test the blower motor housing and the blower motor control circuit in the blower motor harness for a short to ground."
How do I get to the blower motor and blower motor harness?
Thanks!
The "Blower Control Module" may need to be replaced. It has been known to cause this problem of the blower running - key off.
The Blower Control Module is attached to the underside of the HVAC unit next to the blower motor itself.
Follow the blower motor wiring to the control module. (An under dash wiring harness is plugged into the control module, and the control module is plugged into the blower motor)
The control module has slotted mounting holes; do NOT completely remove its mounting screws. Simply loosen the screws to the point that the control module slides off of the screws.
Thread Starter
Safety Car
Joined: Mar 2007
Posts: 3,518
Likes: 37
-
The "Blower Control Module" may need to be replaced. It has been known to cause this problem of the blower running - key off.
The Blower Control Module is attached to the underside of the HVAC unit next to the blower motor itself.
Follow the blower motor wiring to the control module. (An under dash wiring harness is plugged into the control module, and the control module is plugged into the blower motor)
The control module has slotted mounting holes; do NOT completely remove its mounting screws. Simply loosen the screws to the point that the control module slides off of the screws.
The "Blower Control Module" may need to be replaced. It has been known to cause this problem of the blower running - key off.
The Blower Control Module is attached to the underside of the HVAC unit next to the blower motor itself.
Follow the blower motor wiring to the control module. (An under dash wiring harness is plugged into the control module, and the control module is plugged into the blower motor)
The control module has slotted mounting holes; do NOT completely remove its mounting screws. Simply loosen the screws to the point that the control module slides off of the screws.
Great! How do I get to the blower unit itself? Is it under the passenger dash? Can I remove the lower panel to get to it/reach it from below? I've been all over the driver's side dash putting on gauge bezels for people but not the other side so don't know how to get in there. Thanks
