Dead heater blower

[dj1111]

2005 Impala, 3.4L. The heater blower will not run anymore. Was working flaky for a while now is dead. Pulled the motor out and it spins powerfully when connected directly to 12 volts. Checked the voltage at the wires going into the motor (purple and black) and found something weird. At the low end of the fan speed it reported about 4.5 volts. At the high end 12.4 or so. With the ignition off and key removed it still reported 4.55 volts. Could this be a sign of a bad resister? Could the 12.4 volts it's reporting at high speed be extremely low amps and not enough to get the motor spinning?

Thanks for any help.

[Tech II]

When checking voltage to a motor or solenoid, I never use a voltmeter, I use a test light....voltmeter just shows potential voltage, not working voltage....for example, suppose there is a voltage drop in this particular circuit....a voltmeter, reading open ended voltage would read the source voltage, say it's 12 volts...but you attach a test light and it's very dim, or not lit......if you were to take a test light and attach it across a battery, it would be very bright, because all the voltage is dropped across the test light.....but in this case, because there is a voltage drop somewhere in the circuit,, only a portion of the 12 volts is across the test light, making it dim or unlit....

In other words, because of a large voltage drop elsewhere in the circuit, current is low, and not enough to light the test light or turn the blower....

[dj1111]

The car isn't mine, it's a friend of my son's. She had it over to my house again briefly tonight and I did a light bulb test on the wires going to the fan. Would not light the bulb. I tested the bulb by connecting directly to a full 12 volt source and it lighted bright. So back to my original question. If I'm getting the full 12.** volts (heater fan control at high) with a digital meter but so low amperage it won't light a 12 volt bulb is this an indicator that it's the resistor?

Thanks

[Tech II]

Yes, it's the "source" that is the problem....don't know what system you have, manual or automatic.....manual uses a resistor block.....auto uses a blower control module......

You have to check for power into each one.....

[j cAT]

Originally Posted by dj1111

The car isn't mine, it's a friend of my son's. She had it over to my house again briefly tonight and I did a light bulb test on the wires going to the fan. Would not light the bulb. I tested the bulb by connecting directly to a full 12 volt source and it lighted bright. So back to my original question. If I'm getting the full 12.** volts (heater fan control at high) with a digital meter but so low amperage it won't light a 12 volt bulb is this an indicator that it's the resistor?

Thanks

If the vehicle has the maunal blower speed control the resistor/relay module is defective in most cases. removal and inspecting this module you can check for open resistance runs/circuit with an OHM meter or just looking at it if very much damaged . these OEM style are very much damaged. with an older higher mileage vehicle the blower motor can cause a resistor / relay control module go bad in a short period of time, this would be from a higher current draw with a bad motor with shorted windings or bad bushings on the armature shaft.

since it operates with the 12volts good and smooth this is the resistors/relay module. I had to replace mine . just make sure the fuses are good .

[dj1111]

The fuses are good. Speaking of a high current draw. When I connected the motor directly to a 12 volt source, and it started up while holding it in my hand, it torqued quite a bit. Like if I wasn't holding it securely it could have twisted out of my grip. Is this normal? The thing had a ton of power and came up to speed in an instant. It seemed like quite an amp draw.

Oh and it's a manual heating system.

[j cAT]

Originally Posted by dj1111

The fuses are good. Speaking of a high current draw. When I connected the motor directly to a 12 volt source, and it started up while holding it in my hand, it torqued quite a bit. Like if I wasn't holding it securely it could have twisted out of my grip. Is this normal? The thing had a ton of power and came up to speed in an instant. It seemed like quite an amp draw.

Oh and it's a manual heating system.

your description of the motors reaction to being powered up means it is a good motor. If the rotation was sluggish and did not have good torque this would indicate the motor is bad.

the resistors are about 20-25.oo .. I got them at autozone. lifetime warrantee.

[dj1111]

I'm going to be looking at the car again tomorrow. It's starting to get cold up hear in Wisconsin. So much for the incredible warm weather. Anyway, something came to mind when I had the motor out to test it. There seemed to be higher than normal resistance when manually spinning the fan. Like it could be enough resistance to make the motor draw more amps than normal. And I know this could lead to more heat at the resistors and burn things out. Could have lead to the demise of it. I noticed the bottom shaft of the motor armature was exposed so I plan to put a drop of oil on it to see if it works it's way in. I'll also look for a place to put a drop of oil at the top of the motor. It spun smooth but it did not spin free like when you give it a spin and it spins on its own for many revolutions. I'd hate to replace the resistor only to have it burn out in no time. Any thoughts?

[Tech II]

Actually, what usually takes those blocks out,, is water....there is a water dam just above the fresh air opening, if the dam is not in place water gets down it there and the fan throws it across the hot resistor block....good-bye.....

[dj1111]

The resistor in this car is not inside the blower like so many photos and videos have shown online. It is located very close the the firewall completely outside of the blower housing.

[walker12]

the resistor should be in the blower housing because the air flow from the blower cools the resistor. some times the contacts in the blower motor dont get the best connection and it takes a good bump or tap to get the motor turning.

[dj1111]

It looks like the one in the link below and is mounted from the outside of something. It's not inside the housing that is exposed after removing the blower motor. Maybe the heat sinks are inside a passageway of the housing that air blows across. Once I get it out tomorrow I'll know if any water got to it.

http://www.autozone.com/autozone/par...200917_0_3330_

[j cAT]

Originally Posted by dj1111

It looks like the one in the link below and is mounted from the outside of something. It's not inside the housing that is exposed after removing the blower motor. Maybe the heat sinks are inside a passageway of the housing that air blows across. Once I get it out tomorrow I'll know if any water got to it.

http://www.autozone.com/autozone/par...200917_0_3330_

the blower resistor assy is mounted on the exterior of the air box near the blower motor. the electrical connector is outside the air box. however the resistor components are inside the air box. when the blower blows air cools down this resistor.

remove the blower motor and make sure you have no restrictions in the air box/heater/evap with debris.

some have found rodent/lizard nests. where I live you get acorns and other tree debris .

[j cAT]

[quote=dj1111;6933595] Anyway, something came to mind when I had the motor out to test it. There seemed to be higher than normal resistance when manually spinning the fan. Like it could be enough resistance to make the motor draw more amps than normal.quote]

when you spin a dc motor you now have a generator. since there is magnetism in the fields , the armature spinning cuts those magnetic lines of force creating a voltage that distorts the ohm reading.

[j cAT]

Originally Posted by dj1111

It looks like the one in the link below and is mounted from the outside of something. It's not inside the housing that is exposed after removing the blower motor. Maybe the heat sinks are inside a passageway of the housing that air blows across. Once I get it out tomorrow I'll know if any water got to it.

http://www.autozone.com/autozone/par...200917_0_3330_

try advance auto .BWD ru 867 $36.oo lifetime warrantee.