Can Putting In A Blower Relay Wrong Start A Fire
Reading Time: 7 minutes
A very common result with blower resistors is a burned out connector. Blower resistor terminals can develop resistance, and when they do, they get hot and begin to oxidize even further, creating large amounts of resistance where no resistance should exist, heating the wire terminals and the wires feeding them until they scorch and melt the blower resistor connector. Somewhen, the connector terminals become so damaged and oxidized that the blower stops working or perhaps you lot might detect that it only works when you wiggle the wires at the resistor connector.
Usually a unproblematic visual inspection will reveal this kind of failure – the wires at the connector will exist blistered and scorched with missing insulation, and sometimes the melting is severe enough that the connector may be fused to the blower resistor and can't be unplugged.
This kind of failure requires replacing the resistors besides every bit the resistor connector pigtail, but you need to do a really adept task splicing the wires (and don't get them out of order) or y'all'll make bigger problems for yourself.
This meltdown blazon failure can likewise happen at the blower motor connector itself.
Blower Motor Resistor Test
Okay, let's say there'southward no melting going on, merely your fan doesn't work on all speeds. Typically, if the fan will work on some speeds but not on others, the resistor is suspect. If the fan won't work on any speeds except high speed, the blower resistor's thermal fuse may have failed, meaning the entire resistor needs to be replaced.
WARNING: Do NOT bypass the blower resistor thermal fuse if you don't want your motorcar to catch fire!
Here are some tips on how to examination your blower motor resistor:
- Outset by looking for the blower fan resistor. A repair transmission tin can tell you lot where its location is in your vehicle's make and model.
- Inspect the resistor visually. Look for obvious signs of corrosion and burns from overheating. If you encounter signs of overheated connectors, replace the blower resistor and its connector, merely again, you lot must splice the wires correct, or you'll have issues at the splice later on.
- If you desire to do a quick test of the blower resistor, you can check the resistance of each of the resistors with a multimeter as follows: gear up the tool to read ohms (a measurement of resistance) and connect 1 of its probes to the common output terminal of the resistor. Use the other probe to measure the resistance between the output terminal and each of the resistor's input terminals. Measure the resistance between one pair of terminals at a time. Of course, to exercise this, you need to know which concluding is the mutual terminal (information technology's the one directly feeding the fan motor). And you'll besides need to know which of the other terminals is which speed – you tin find this information in an online wiring schematic for your vehicle if you know where to look.
- If whatsoever of the points bear witness infinite resistance, the blower motor resistor has failed. Infinite readings denote an open up circuit.
Be careful when treatment the blower resistor. Since electric currents pass through the resistor for extended periods, the device can build upwardly significant heat—plenty to burn your fingers or worse.
What is a Blower Motor Resistor and What Does it Practise?
The blower motor resistor controls the fan speed of the blower motor and the resulting change in air pressure produced by the motion of the blower fan. It accomplishes this by regulating the electric electric current that powers the motor.
How Does a Blower Motor Resistor Work?
On climate control systems without automatic temperature controls, the blower motor speeds are controlled by a switch wired to a stepped resistor that ordinarily includes a thermal fuse. Because resistance creates heat while current is flowing, the blower resistor is mounted in the duct near the blower motor so the resulting airflow will go on the resistor absurd.
If the fan malfunctions (similar if the fan shaft is spinning in the blower muzzle hub without spinning the cage) so that no air is moving past the resistor merely current is still creating heat in the resistor pack, the thermal fuse that is integral to the resistor assembly opens the electrical circuit to forbid the resistor(s) from getting too hot.
To sympathize how the blower resistor works, a simple electrical principle chosen "voltage drop" is used. When a switch, a resistor, and a load are wired in series, the resistor "drops" some of the voltage passing through it, effectively reducing both current flow and voltage at the motor. A voltmeter connected to both ends of a resistor while current is passing through it to a load volition measure out the amount of voltage beingness "dropped" by the resistor. Because lower voltage means lower electric current delivered to the fan, the stepped resistor circuit can be used to control fan speed.
The blower switch and its gang of resistors are wired so that when the blower switch is set at the everyman speed, the maximum amount of voltage is dropped and the least amount of current is fed to the motor considering information technology is passing through an unabridged serial of resistors – for our purposes we'll say there are three resistors.
In the next highest speed, one of the three resistors is bypassed and since the voltage is only having to push the current through two resistors, the fan motor runs a scrap faster. In the adjacent highest speed, two of the three resistors are bypassed and but one resistor remains in series with the motor (load).
Finally, with the fan switch on the highest speed, the fan motor is receiving organisation voltage (14.five with the engine running). Some systems will energize a relay when the switch is fix at the highest fan speed. The relay so closes its contacts, feeding full voltage to the fan, because a relay can handle the electric current better than the fan switch.
Many blower fans volition take a relay delivering power to the "hot" fan terminal and the blower resistor will provide the path to ground.
What are the Symptoms of a Bad Blower Motor Resistor?
Every time you fiddle with the fan speed of your motorcar's air-conditioning or heating organisation, you change the current that flows through the blower motor resistor on the way to the blower motor.
A bad or declining blower motor resistor hampers the efficiency of the heating and ac arrangement. The most mutual symptoms include:
The Blower Only Works on Higher Speeds
A working resistor can shift betwixt speed settings according to the user's preference. If one of the resistors is burned out, the just speeds that will work are the speeds above the burned out resistor.
A blower stuck on a high-speed setting will keep blasting you with hot or cold air when you don't demand it, though one that's stuck on the depression setting can be just as frustrating.
This symptom isn't limited to a bad blower motor resistor. A broken blower motor switch tin also stop the blower from changing to certain speed settings. If your blower motor cannot change to certain speeds, check both the resistor and the switch on your dashboard. The virtually mutual failure points are the resistor and the motor itself.
No air comes out of the vents
There are instances where a bad resistor will prevent the electric current from reaching the blower motor birthday. Without any power, the motor won't run. As a consequence, the blower fan stays still and silent, and no air blows out of the vents.
This symptom can also stem from a failed blower fan or several other issues, such as:
- Burned connectors or thermal fuse failure
- Blown fuse or circuit breaker
- Faulty switch or wiring
- Bad ground
Causes of a Bad Blower Motor Resistor
Resistors take information technology rough. They always have electricity flowing through them, and the voltage can change sharply as you conform the strength of the blower fan.
The most probable reasons for blower motor resistor failure include:
- Corrosion from long exposure to air and moisture
- Overheating—if a motor finds information technology harder to move because of jamming or worn bearings, it can raise the resistor'southward temperatures to dangerous levels.
- Normal wear due to time and use
What is the Cost of a Replacement Blower Motor Resistor?
You can still drive your car despite a faulty blower motor resistor. However, yous'll probably discover it uncomfortable to have the blower running at one speed setting the unabridged time or having express access to certain settings.
Depending on the manufacturer and model, a blower motor resistor tin can go anywhere between $three and $335 on CarParts.com. The replacement parts come in individual units, sets of 2 resistors, or every bit role of a blower motor resistor kit.
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Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.
Can Putting In A Blower Relay Wrong Start A Fire,
Source: https://www.carparts.com/blog/how-to-test-a-blower-motor-resistor/
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