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If you mean that the Daytime Running Lamps (DRL) does not work when the blower motor does not work, then YES it COULD be an ignition switch problem. However, not very likely (please read on). The regular HIGH and LOW beam headlamps do not require the ignition switch to operate.
The main circuit that runs your regular headlamps also runs the blower motor HIGH speed. This has nothing to do with the ignition switch. This circuit also operates the Power Mirror circuits and the Hazzard Flashers. You may want to check to see if these are also malfunctioning when this happens.
The Circuits for your other blower speeds go through the ignition switch along with the DRL control module, but your HIGH speed does not. So if it is your ignition switch, your HIGH speed should still work and your regular headlamps should still work. You will lose only your lower blower speeds and DRL if it is an ignition switch problem. You will have a bunch of other stuff going out if it is an ignition switch also. The ignition switch circuit that runs your DRL module also runs your Powertrain Control Module. So if it is an ignition switch problem causing your DRL to shut down, your engine will also be shutting down.
If the blower is making noise than the only thing you can do is replace it.
Blower resistors typically operate by dropping voltage through a set of resistors. The lower the speed the more resistance is needed. High speed requires no resistance and usually bypasses the resistor assembly.
The switch, high blower speed relay or the wire harness at the blower motor has gone bad. The
highest setting 5 has no resistor, so the blower runs on high but the
high current flow ends up burning up the switch's contact on that
setting or the relay and may be the resistor wire harness at the blower motor has gone bad.
Common would be the switch it self, if the switch is good. Then it's
going to be the blower relay or wire leads at the speed resistor by the blower motor
under the glove box by the passenger leg compartment. Keep me posted,
be glad to help you get your Silverado running 100% again soon.
When the light is blinking that means there is a code in the system you will have to take it to a shop and have the codes read. Sometimes "Jiffy Lube" or "Rapid Oil Change" can read the code for but they won't fix it. If the blower motor only runs on high, the blower motor resistor is bad. When you put the fan switch on high it puts full voltage to the fan motor (blower motor) when the fan switch is in any other position, the voltage is reduced by the resistor causing the motor to run at slower speeds. The two problems are probably a result of the resistor.
The blower resister is near the blower motor,mounted on the outside of the blower box,but actually goes inside the blower box.It~s function actually is to give the blower motor lower speeds.If it is only working on high,then this is the problem.If it works on high when you select a lower speed,then there is a high blower motor relay that is stuck in the closed position .Replace the relay.
Usually when the blower fan only operates on hi speed, its because of a failed blower motor resistor. You still have hi speed because on hi, the power going to the blower motor goes directly to it, as opposed to the lower speeds, when the power is routed through the resistor, thus lowering the voltage, which in turn lowers the speed of the fan. The resistor is usually located near the blower motor itself, under the hood back near the firewall.
The resistors are in circuit only on the lower fan speed settings.
On the highest speed setting, power is switched directly to the fan motor.
Check fan power supply fuses,
Check power is available to the fan when high speed selected.
If all above OK, apply power directly to the motor to verify fan motor runs- if it doesn't the motor may need replacement/repair.