Tip & How-To about Chevrolet Venture

Blower motor does not work?

Blower motor problems are a pretty common topic. This is a basic guide on how to diagnose the problem and will work for most vehicles.

The diagram is generic and loosely based on GM's setup and more specifically a Silverado. Most manufacturers have a similar setup and the only major differences would be a ground side control (instead of the switch supplying power to the resistor it would be grounding the power from the resistor if this is the case you test light would need to be connected to power to test the switch) and late model Chrysler minivans (they use a module that looks for a difference in a/c voltage from the switch)

If the blower works on high only than likely the resistor assembly is the culprit since power to the blower essentially bypasses all of the resistors and/or the resistor assembly entirely. The reason why none off the other speeds will work is that the resistor or the circuit for the speed four setting has burned out. The lower the setting the more resistance you need to drop the voltage to the blower. The first speed setting requires all four resistors to drop the voltage enough to turn the blower at its slowest speed. Speed 2 needs to turn the blower a little faster so it uses three resistors. Speed 3 uses two resistors and speed 4 uses one.

In some cases the fan will work on high and speed setting 4. The likely cause for this is the speed 3 resistor or circuit has burned out. Speed 4 still works because it doesn't use the lower speeds resistors to control the speed of the blower. If the speed 2 resistor burns out than speed 1 and 2 will not work but 3, 4 and high will continue to work. If the speed 1 resistor burns out than speeds 2, 3, 4, and high will continue to work.

This leads us to how do we know if its the resistor or the switch or the blower. If the blower works on high than we know the blower works. That leaves us with either the switch or the resistor assembly (there are many other possibilities) which can be easily tested with a test light (or a voltmeter if you choose) The first thing to do is locate the resistor assemble. They can be behind the glove box, under the dash close to the blower motor or under the hood, again usually close to the blower motor. It will typically have 5 to six wires going to it. We'll start by unplugging the connector, turning the key on and connecting your test light to ground.

1.Turn the switch to high and backprobe all the wires. Two of them should illuminate the test light. In the diagram below this would be wire E & F. If you don't have a diagram then hold the test light on one of the two wires and move the switch to another speed setting. the wire that continuously illuminates the test light regardless of the switch position will be the constant power for high blower speed and will not need to be rechecked in the following steps.

2. Turn the switch to the next lowest setting. Backprobe the remaining wires to see if one of them illuminates the test light. Repeat until you have checked all of the speed settings.

3. If the test light has illuminated a different wire for each setting then we can reasonably assume that the switch is functioning as intended and the source of the problem is the blower resistor.

If you find one or more settings (but not all the settings) on the switch that does not illuminate the test light on any wire than we can reasonably assume that the switch has failed.

There are a few other things that can cause blower motors not to work as intended. The switch or the resistor assembly are the two most common problems.

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2000 ford explorer ac fan in front does not work, rear blower does work, where should I start looking for problem


Front HVAC blower motor, Heat & A/C ! Viewing wiring diagrams an testing the electrical circuit's using a DVOM - digital volt ohmmeter is how you start a diagnose's . Do you know how to do that ? It's not hard if you have right training .
Lot's of video's on youtube .
Electric Testing Techniques You Need to Know
free wiring diagrams here http://www.bbbind.com/free-tsb enter vehicle info year , make , model an engine size . Under system click on HVAC , then under subsystem HVAC controls . Click the search button ,then the blue link's . Looking at the two link's i see that your vehicle could have blower motor relay's an resistor or blower motor speed controller. Knowing what your looking for can be a challenge .
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04 iMpala LS blowr motor stopped! here are the stats: *right dash fuse was ok *big 30amp fuse was ok *new blower resistor *multifunction switch working fine *low miles on car.


Finding a wiring diagram an using a DVOM - digital volt ohm meter an testing the electrical circuit is the proper way to diagnose electrical problems . Looking at the wiring diagram for your vehicle i see it doesn't have a blower motor resistor , it is a blower motor contol processor . Electronically controlled .
HVAC Blower Motor Circuit
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Only the fan climate control is not working. The display climate control is working but only the fan.


That is the heater / AC blower motor ! There are electrical circuits and relays and blower motor resistor , blower motor etc... Electrical testing is the way to diagnose blower motor circuit . Looking at a wiring diagram to see what controls the blower motor on your particular vehicle would be the first step in diagnosing your problem . Do you know how to do automotive electrical testing , how to read or follow a wiring diagram ? Videos on youtube show how to test blower motor and related parts and wiring . Blower Motor and Resistor Diagnostics by Wells

Dec 29, 2016 | Cars & Trucks

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Heater won't turn on sometimes, or turns off by itself and only works on High.


I can't diagnose unless you can do some testing? This is part of diagram for automatic hvac. At the blower motor, terminal B is voltage, terminal A is ground. Use a test light, check voltage and ground with hvac on, Have to check when problem is ongoing. If good voltage and ground with no blower action, suspect the blower motor is faulty. Of course, if your missing voltage or ground, have to track that circuit. Faulty blower motors may run intermittently. When problem is ongoing, hvac on, you can try tapping blower motor with screwdriver handle see if it starts running, if it does, I suspect the blower motor has a problem. Check hvac trouble codes, where applicable.
blower motor-glvii1gxkt1idx3zyylb1u0i-1-0.jpg

May 30, 2017 | 2001 Buick Century

1 Answer

I would like to know how I can fix the heater in a 89 gmc k1500 with a 350 engine and no air. I tried a new heater motor and still not working. The Fuse is also good.


This is a blower motor not working tip I posted a little while back.

Blower motor problems are a pretty common topic. This is a basic guide on how to diagnose the problem and will work for most vehicles.

The diagram is generic and loosely based on GM's setup and more specifically a Silverado. Most manufacturers have a similar setup and the only major differences would be a ground side control (instead of the switch supplying power to the resistor it would be grounding the power from the resistor if this is the case you test light would need to be connected to power to test the switch) and late model Chrysler minivans (they use a module that looks for a difference in a/c voltage from the switch)

If the blower works on high only than likely the resistor assembly is the culprit since power to the blower essentially bypasses all of the resistors and/or the resistor assembly entirely. The reason why none off the other speeds will work is that the resistor or the circuit for the speed four setting has burned out. The lower the setting the more resistance you need to drop the voltage to the blower. The first speed setting requires all four resistors to drop the voltage enough to turn the blower at its slowest speed. Speed 2 needs to turn the blower a little faster so it uses three resistors. Speed 3 uses two resistors and speed 4 uses one.

In some cases the fan will work on high and speed setting 4. The likely cause for this is the speed 3 resistor or circuit has burned out. Speed 4 still works because it doesn't use the lower speeds resistors to control the speed of the blower. If the speed 2 resistor burns out than speed 1 and 2 will not work but 3, 4 and high will continue to work. If the speed 1 resistor burns out than speeds 2, 3, 4, and high will continue to work.

This leads us to how do we know if its the resistor or the switch or the blower. If the blower works on high than we know the blower works. That leaves us with either the switch or the resistor assembly (there are many other possibilities) which can be easily tested with a test light (or a voltmeter if you choose) The first thing to do is locate the resistor assemble. They can be behind the glove box, under the dash close to the blower motor or under the hood, again usually close to the blower motor. It will typically have 5 to six wires going to it. We'll start by unplugging the connector, turning the key on and connecting your test light to ground.

1.Turn the switch to high and backprobe all the wires. Two of them should illuminate the test light. In the diagram below this would be wire E & F. If you don't have a diagram then hold the test light on one of the two wires and move the switch to another speed setting. the wire that continuously illuminates the test light regardless of the switch position will be the constant power for high blower speed and will not need to be rechecked in the following steps.

2. Turn the switch to the next lowest setting. Backprobe the remaining wires to see if one of them illuminates the test light. Repeat until you have checked all of the speed settings.

3. If the test light has illuminated a different wire for each setting then we can reasonably assume that the switch is functioning as intended and the source of the problem is the blower resistor.

If you find one or more settings (but not all the settings) on the switch that does not illuminate the test light on any wire than we can reasonably assume that the switch has failed.

There are a few other things that can cause blower motors not to work as intended. The switch or the resistor assembly are the two most common problems.

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I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

Nov 09, 2010 | 1989 GMC Sierra

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