What you’ll need for this fix / car repair tutorial

You will need the following new parts and tools to perform this repair;

• 1-Blower Motor Resistor
• 1/4″ nut driver
• 7/32″ socket
• 1/4″ universal/wobble

With a short explanation and basic understanding of electrical functions in the automotive world, you can understand how and why these parts fail for future reference. The car being used in this article, is a 2002 Pontiac Grand Am

Price Comparison – How much you can save

Repair shop pricing
Parts-approx.$60
Labor to diagnose 1 hour($80), labor to repair 1 hour($80)
Total cost-$220 plus tax

Do it yourself
Parts-$30 (from your local parts store)
Estimate time to repair, approx 30 min to 1 hour
Total cost-$30 plus tax

Step 1 – Identify the problem

Lets start with speed number 5.

The battery voltage is at full potential when you switch it to speed #5 (approx-12.5 volts). In this position the blower motor runs at high speed as fast as it can.

Reference Note

For a better understanding of electrical diagrams you can refer to automotive electrical theory in Automotive Electrical 101 – Part 1

Follow the silver line through the wiring schematic. This is the path that the voltage is traveling through setting #5/high speed.

When switching to speed #4 the voltage goes through a resistor before reaching the blower motor. This resistor takes away approximately 2 volts. Now with 10.5 volts supplied to the blower motor, it runs at a little bit slower pace. It blows fast, but noticeably slower than speed #5.

Note:This illustration is a 4 speed blower circuit. The point is to show you how the speeds are controlled by resistors.

Speed #3 adds one more resistor in series for the circuit. Now take away 2 more volts. Now the blower motor is running at 8.5 volts. Each speed is supplied with a smaller amount of voltage, thus allowing the blower motor to slow down.

Speed #2 and speed #1 work on the same principle.

If you take a circuit and put a resistor in the path of current flow, you will restrict the path, only allowing a certain amount of voltage and current to be supplied to that load device. In this case, the blower motor is our load device. Now you can see that when a blower motor resistor goes bad, you can lose your lower speeds and still have the highest setting.This should give you an understanding of how the voltage is controlled in a blower motor circuit.

Locating the Resistor

GM usually puts the blower motor and resistor next to each other. Nine times out of ten, both of them are accessible from inside the car. The blower motor and resistor in this Grand Am are mounted in the bottom of the heater box in the passenger footwell area.

Start by removing the lower trim under the glovebox.

The attaching screws can be removed with a nut driver and a 7/32″ socket.

Once the 2 screws are removed, pull out the panel.

Note: The only tools needed for this job is the 1/4″ nut driver, 7/32″ socket, a 1/4″ universal/wobble socket, and a light to help see the work area.

Position the passenger seat as far back as possible. This will allow you enough room to lay in the floor area to see and work while replacing the resistor.

Here is the view with the panel removed. The round component is one end of the blower motor.

The black and blue electrical connector behind the motor is where the resistor is located.

In order to access removing the resistor, the blower motor will have to be removed first.

Replacing the Blower Resistor

The alarm module will need to be removed. Pushing the module to the right allows it to slide out of it’s bracket.

Don’t bother unplugging the module, there’s enough room to work around it hanging down.

Remove the 3 hold down screws.

Use the same nut driver and socket, but add the wobble attachment.

With the blower motor screws removed, pull the motor straight down for removal. Be cautious not to pull the motor to the side until the blower cage clears the housing. This is to prevent damage to the cage assembly.

Unplug the blower resistor

Remove the resistor mounting screws.

Pull out the old resistor.

Here is what a blower resistor looks like.

Compare the old resistor with the new one to make sure they look alike.

Compare the electrical terminals also, and make sure they are identical.

Install the new resistor and screws.

Plug in the resistor.

Reinstall the blower motor.

Be sure to test the operation of all the blower speeds before reassembling the lower trim.

If you need help locating and pricing parts for your own car refer to Locating a good source to purchase parts

How do you determine how a electrical circuit works and how to test it? In the first section you’ll learn basic electrical theory and how to trace current flow in an automobiles electrical circuit. I will also explain wiring diagrams and how to read them.

There will be many up and coming articles about tracing and repairing electrical circuits within today’s vehicles so please make sure to check back for more.

Starting thought

Before attempting to diagnose or repair any type of electrical circuit you need to understand and know how electricity works in today’s automobiles.

I could talk all day long about electron flow theory, but with simple explanations of how, where, and why electricity operates, I will teach you what it takes to understand and diagnose simple automotive circuits. Here is a crash course on how it works.

Define Electricity:

Electricity is a controlled movement of electrons from one atom to another.

What does this mean and how does it relate to automotive technology?

What this means is, anything that is electrically operated on your vehicle operates by electrons moving through each circuit. When you have a power source like a car battery, you have a way to make these electrons unstable and wanting to move about. These unstable electrons are now your electrical source to power up objects that you can use in today’s cars. Electric motors are everywhere in your car. These motors operate your windows, sunroofs, seats, wipers, heater blower, cooling fans, and even the starter on your engine. These are only a few to mention.

I’m going to use these objects I’ve mentioned, and put together a circuit that is something you will see on today’s cars.

Basic electrical circuit

• An electrical power source
  (the car battery)
• A load device
  (something to use electricity to perform a working task ex; bulbs, motors, etc)
• A control device
  (this would be a switch or control unit that creates an open within the circuit)
• A path for the voltage and current to flow between these two objects
  (this would be the wiring to complete the circuit)
• A protection device
  (a fuse or circuit breaker, this would prevent an electrical meltdown if something failed in the circuit)
• Connectors
  (these allow sections of the circuit to be connected together and are easy places to test within the circuit when problems occur)

Electricity always leaves the battery positive side and flows to the load device which uses the voltage only, allowing the current or amperage to return back to the battery negative side completing the entire circuit. If there are any breaks or opens in the circuit, the voltage will only be present up to the break and not allow the circuit to operate. This is why it is important to have a good ground on electrical circuits. The ground paths use metal or frame areas through out your vehicle and return back to the battery.(We refer to this as chassis ground)

Plan ahead

Before doing any type of on car diagnosis, you should have a plan of attack. This means map out your electrical testing steps on a wiring diagram. Just like taking a road trip or vacation of some type, you probably wouldn’t just take off on a long trip without knowing where you are going ahead of time.

Every component in a car has an electrical diagram to show the circuit layout. Over the next few electrical articles I’m going to show different circuits, explain how they work, and list all the symbols used in these circuits. Here is a horn circuit, I’ll walk you through where the power comes from all the way through the circuit wiring, horn, and back to the battery ground.

Typical wiring diagram

Electrical circuit breakdown

The first thing to always remember is the power source always starts at the top of the page and flows down. Here you can see the text Hot At All Times on the left. This means no matter which position the key is in, off, position 1, 2, or cranking there will always be battery power present to this circuit.

Just below that you will see Fuse 13 /20A. This means the protection device in this circuit is a 20 amp fuse in position 13 of the Under hood Fuse/Relay box. (Note the dashed line around the fuse box, this represents a partial view of the box and there is more to it)

In the center is the Horn Relay. The relay is a electromagnetic switch that controls the power to the horns. The coil is on the left of the relay and the switch is on the right. When the coil is energized, it’s magnetic field pulls the switch and sends power to the horns. Notice the box around it is solid. This means it’s a full view of this component. Just above the relay there is a dot where the two wires split from the original wire, this is a splice in the wiring that is a soldered or permanent connection, this doesn’t come apart like a connector. The relay is located inside the Relay Control Module, which is inside the Under hood Fuse Box.

Note the 3 wires coming out of the fuse box and going down. They have letter and number designations next to them. (I9, M5, M6) This is for reference when trying to find their location on the car. The I and M are different connectors, and the numbers represent where the wire terminals are in the connector. (terminal 5 for one wire and terminal 6 for the other)

On the left of the wires are designated color codes for the wires. GRN/YEL is a green wire with a yellow stripe. BLU/RED is a blue wire with a red stripe. In the middle of the GRN/YEL wire is a C401 /18. This “C” always represents or stands for connector. The 18 represents the terminal inside this connector. C405 is another connector and E1, F1, and G1 are the terminals inside the connector.

This section shows the GRN/YEL wire going through 2 components. The first is connector/terminal B1 of the partially viewed Cable Reel. The cable reel is a special coil of wire that rotates within the steering wheel. The wire continues out of connector/terminal C1 on to the partially viewed steering wheel.

The other two BLU/RED wires continue on down the diagram to the next component.

Once inside the steering wheel, the GRN/YEL wire changes color to a BLK wire. (black) This wire continues on to the horn switch (full view) which is inside the partially viewed steering wheel. At the bottom of the steering wheel there is a dot with 3 small lines attached horizontally, this is the symbol for a ground.

On the right, the two BLU/RED wires continue on to the horns. One low tone horn and one high tone horn that have separate grounds.

Now that I’ve described each symbol and component on this diagram, I’m going to explain how the voltage and current flows through the circuit.

Understanding what electricity is

All automotive electrical circuits have 3 things that are constantly talked about, voltage, current, and resistance. These 3 things are what it takes to operate a circuit. The direct relationship between voltage, current, and resistance is most commonly referred to as ohms law. (more on ohms law later)

Voltage is referred to as EMF, the Electromotive Force that supplies electrical energy to the circuit. Coming from the battery it’s the electrical pressure that pushes current through the circuit.

Current is the electrical flow within the circuit. What is flowing? Electrons!! Lets go back to our definition of electricity; a controlled movement of electrons from one atom to another. Electrons are the current flow. All matter is composed of atoms which are full of electrons that can be stable or unstable depending on their environment. In this case, our battery is an electrochemical device that is designed to make electrons unstable. (more about battery’s later)

Resistance is a restriction to the current flow. Using the horn diagram, the horns are the load device in this circuit. They restrict the current flow. As voltage and current are traveling down this circuit to the load device, they are searching for a path to ground. The horns operate by using the voltage to perform a task. A horn is basically a loud speaker. When activated, the horn will use the voltage and allow the current to flow back to the battery creating a constant flow of electrons in a complete loop or path called an electrical circuit.

Wiring Diagram Review

In reference to the horn circuit diagram, here is how the circuit works. The battery power supply is hot at all times through the under hood fuse box and fuse 13 to the horn relay. The power supply feeds both the coil and the switch inside the relay. Here is where I make you think. The coil power on a working circuit stops here because in order to energize this coil to make it a magnet for pulling the switch, we need to ground the other side of the relay coil. If you follow the GRN/YEL wire through the rest of the circuit, the horn switch that you push to honk the horn completes the path to ground. Now with the relay energized, the switch is pulled closed to send power down to the horns that are already grounded, waiting to sound off. This is how the horn circuit works.

Key Electrical Terms

(Key terms in bold throughout this post)

Note:

Now that your through with Automotive Electrical 101-Part 1, you can refer back to System 101 for more automotive topics

Coming Soon

• Automotive Electrical 101-Part 2 (Digital multimeter usage)
• Automotive Electrical 101-Part 3 (Testing inoperative and shorted circuits)
• Automotive Electrical 101-Part 4 (Measuring voltage, current and resistance in a circuit)

Keep in mind that every vehicle is different when it comes to similar repairs. Here is a 1995 Jeep Grand Cherokee that had a customer concern of the driver’s window moving slow and stopping in mid travel. This is a relatively easy repair on a Jeep Cherokee when compared to other vehicles.

Open the door and locate where the panel screws are.

This panel has 4 screws and a dozen or so reusable clips.

All of these are #2 Philips screws

Each recessed area has a screw to secure the panel.

One screw in the inner door handle

There’s a hidden screw under this cover.(Pry out cover with a small flat blade screw driver)

Pull the handle trim cover toward you and lift the trim cover over the release handle.

The panel is only held on by clips at this point, pry out at the bottom and then the sides.

Lift the panel off of the door by grabbing the inner handle and pull it up and toward you.

Disconnect the wiring connector for the window switches by pushing a release tab and pulling apart.

Remove the panel and the black moisture barrier,(The moisture barrier helps to keep out wind and rain)

Now you can see the window regulator and motor in the door.

Start by locating where the glass attaches to the regulator, you might need to connect the switch to power down the window.

Loosen and slide the regulator left to allow the glass to separate, slide the glass up and tape to the door edge to hold.

Locate the mounting bolts, remove the top and loosen the bottom.

Here is a second slide bolt, loosen but do not remove.

Remove the last two mounting bolts. See the large access hole at the base of the door from where to remove the regulator.

Don’t forget to unplug the window motor.Lift the tab and pull apart.

Once removed, this is what the whole assembly looks like.

Be very cautious not to pinch your fingers in the folding mechanism when separating the motor from regulator!!

This regulator has a tremendous amount of spring tension.

Have someone secure the regulator when removing the motor bolts. Keep your fingers out of the way!!

Make sure the window motor is identical to the old one.

If you buy a new motor the connector comes on it, remanufactured motors don’t come with one. You will have to cut the old connector off and solder it onto the remanufactured motor.

The rest of the procedure is in the reverse order of removal.

Bolt the motor onto the regulator assembly and put the regulator into the door and attach the mounting bolts.

Once the regulator is bolted in place, slide the window down and slide the regulator attaching bar over nuts on window glass mounting fixture. Don’t get carried away when tightening these nuts, you don’t want to break the glass.

Plug in the motor to the harness, install the moisture barrier, and door panel.

Attach the panel by pushing the clips into place and installing the screws.

Check the window to make sure it’s operating properly.

Comparison pricing

Just to get an idea of how much you can save by doing this job yourself, here’s a comparison pricing of the two.

If you paid a repair shop to fix your window, add a 100% mark up on the part and at least 2 hours labor at $80.00 an hour.

Window repair by doing it yourself: $75.00 with a lifetime warrantee.

Window repair at a repair shop: $310.00 plus tax with a 12 month warrantee.