However, there are a few vehicles out there that make it extremely difficult. A likely cause for a busted AC or heating unit is a damaged blower-motor. Remember, you need a good ground to complete the circuit. A lack of airflow from your vents is a clear indicator that it may be time for a heater blower motor replacement. The resister block used on many models is coupled with a control module. The control head then sends a command to the motor controller to change the speed to the driver’s preferences. Today I get in the car and it only works on high again. Features to Consider. Could the resitor be bad again. Also, check the fuse for the control side of the high speed relay. Unfortunately, youâll need a digital scope or scan tool to test those components, so your only option may be to replace the parts one at a time. This is to provide an ample supply of fresh air in the interior compartment even when no climate control mode is selected. Disconnect it from the motor shaft and set aside. They mount the resister block in the air conditioner or heater case, because of the generous amounts of air flow. This one has been a big issue over the years. 15. DIAGNOSING THE PROBLEM Blower motor breakdown can be the result of anything from old age to failed bearings, high amp draw, electrical failure in the windings, dirt accumulation, and more. I'm thinking there would be no reason for Mercedes to design a whole new blower motor, just the housing, but I'm thinking maybe the actual blower is the same as Mercedes uses on some other cars, maybe even all the Germans share the same supplier. Two common reasons for this to happen would be drawing too much amperage or a problem with the resister block mentioned above. The easiest way to check for a failure is to start the vehicle and turn the climate control on. Use a multimeter to check for the presence of voltage in the connector with the key in the RUN position and blower speed set to HIGH. Here's a handy guide on …, Have you noticed a foul smell coming from your car? …, When you need your automobile to always stay in great …, Every year, more than 6 million car accidents take place …, blower motor problems page for Chrysler and Dodge owners, 4 Possible Reasons Why Your Car Smells Like Burning Rubber, Drive With Confidence by Buying the Best All Seasons Tires for Snow, In-Depth Guide to Restoring Muscle Cars for Beginners, 5 Must-Have Qualities When Choosing a Car Repair Shop. See the wiring diagram below for that setup. Testing the blower motor is as simple as applying battery power and Ground to the blower motor terminals. As an example on GM cars from the 80s and 90s there’s a 20 amp under the dash. See the wiring diagram for that setup below. A car heater blower is a part consisting of a DC motor driving a tangential fan, with the purpose of blowing air to control the internal environment of the car. With that said, failed blower resistor assemblies don't solve all of the possible failures. Use a multimeter to check for the presence of battery voltage in the connector with the key in the RUN position and blower speed set to HIGH. When that happens, you lose that speed. If you have a three or four speed blower motor, remove the ⦠I have a dedicated page on how to find electrical shorts if you need more assistance in that area. Or, carmakers can opt for a motor resistor AND a high speed relay. Photo: familyhandyman.com. So you have to refer to the factory legends to learn the identification symbols and then refer back to circuit diagrams to find the splice and ground locations. Disconnect the negative and positive power supply. Depending on the exact location of the blower motor (on your specific 3.8 liter equipped GM vehicle) you can test it on the car or you may have to remove it for ease of access. The replacement of parts in the blower motor system are some of the easier repairs to perform on the automobile. âThe most common cause is dirt accumulation due to lack of maintenance,â said Tom Beaulieu, president of Bay Area Services Inc. in Green Bay, Wisconsin. In one design, the car maker supplies battery power to the speed switch, which switches the power to the appropriate connection on the blower motor resistor. Blower motor is drawing too much power. At that point the suspects are the blower motor speed control module (most likely) or the HVAC control head (less likely, but not unheard of). Typically it's done by measuring the voltage at the blower motor connector when it's turned on. Do you set the temperature and the system keeps that temperature or do you have to adjust the temperature up manually and then turn it down once the cabin heats up? Replace the blower motor. The squealing noise happens most often in the winter during cold startups and may disappear as the motor heats up. A resister block will adjust its total resistance as selected by the driver from the switch. Remove the screws, and swap out the resistor module. The motor should run on high speed. Using a multimeter set on the Ohm scale, use the positive lead and test the black wire. Because most automatic systems use an electronic motor controller while manual systems usually use a blower motor resistors to obtain 3 or 4 different speeds. Check the blower motor at its two-wire connector for power. 2. Exhaust leaks can become a serious issue if they aren't taken care of early enough. If it’s in the engine bay you’ll most often find it near the firewall. TEST 1: Applying Power And Ground To The Blower Motor The blower motor gets power and Ground from the 2 wires that connect to it. The reason Iâm not including the motor resistor as a suspect is because it usually only controls the lower speeds. Tools and materials needed: â 4-in-1 screwdriver â Nut driver. Here are the blower motor fix steps: Determine if you have a manual or automatic heating system in your vehicle? It reviews best practices for diagnosing common electrical problems. Swap the high speed relay with another relay with the same part number. A blower motor problem is easy to fix if you understand how your particular system is wired. This is a symptom of a failing blower motor bearing. 1. Basic instructions on how to troubleshoot the heater blower motor of a Saturn S-series. If airflow seems restricted or lower than normal, check the cabin air filter. Run a fused jumper from the battery to the power side of the motor and connect a temporary grounding jumper to the other motor terminal. No noise, no prior problems. With our wide variety of replacement AC heater blower motors, AutoZone can help make your ride enjoyable again - no matter what you drive. This can be annoying, but troubleshooting is easy. I believe General Motors first used it in the 70s. GM called this astro ventilation. Heating systems with just 3 or 4 speeds use a motor resistor along with the speed switch to regulate the motor speed. Purchase a new resistor module at the auto parts store (usually less than $25). They do this for cooling purposes. Don't ignore it! Common Problems with Blower Motors. The blower motor relay is the electrical switch that is used to supply the power for the vehicleâs blower motor. Using the above troubleshooting steps will help you decide if you need to replace your air conditioner blower motor. Blower motor doesnât shut off. 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