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Discussion Starter · #1 ·
I replaced my blower motor last year with a autozone motor.
I noticed the voltage gauge would drop when I turned it on.
I just installed a 160 amp 3g alt but when I turn on the blower motor it still drops from 14.4 volts to 13.2 volts. I would have thought the 3g would handle the blower motor. Does anyone else have a voltage drop when they turn on the blower? And if its a bad motor can anyone recomend a good brand motor to buy?:thumbup

Thanks Mark
 

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Discussion Starter · #6 ·
I bet your not measuring it at the battery
No I'am looking at the dash gauge and a digital gauge mounted in my bronco that goes to a 3 farad capacitor fed by a one 0 wire on my stereo system. Voltage drop is voltage if its at the battery or somewhere in the electrical system. I can turn up the volume on my stereo 1400 watts and there is no drop in voltage with the 160 amp 3g.

The brand of the autozone motor is unknown to me but it is not a seimens.

It just seams to me the motor is pulling a excisive amount of current but that my be the nature of it. I have no way of knowing how much current it is spected for (from ford) except for the 30 amp fuse that supplys it. Iam sure they fused it higher and it doesnt pull 30 amps.
 

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No I'am looking at the dash gauge and a digital gauge mounted in my bronco that goes to a 3 farad capacitor fed by a one 0 wire on my stereo system. Voltage drop is voltage if its at the battery or somewhere in the electrical system. =
Not quite right. There are several grounds in a Bronco and if the ground for the particular circuit isn't there anymore (corrosion, broken, missing), it will affect the available current and draw down your voltage since it has to find another path to ground.
 

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Discussion Starter · #9 ·
Don't blame the alternator if the voltage at the battery is within spec.
If you read my posts I never said anything about the 3G being bad. What I said is last year I had this problem after I replaced the blower motor. I installed the 3G last month and doubled my amperage and I still have the problem. All Iam asking for is a opinion on the possibilities that would cause this problem.:doh0715:

Not quite right. There are several grounds in a Bronco and if the ground for the particular circuit isn't there anymore (corrosion, broken, missing), it will affect the available current and draw down your voltage since it has to find another path to ground.
That is a possibility as the fan speed switch is switching the ground wire through the blower resisters. Thanks Ill check it out.:thumbup

Thanks Mark
 

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If you read my posts I never said anything about the 3G being bad.
BUSTERBRONCO said:
I just installed a 160 amp 3g alt but when I turn on the blower motor it still drops from 14.4 volts to 13.2 volts. I would have thought the 3g would handle the blower motor.
And if you reread my posts, I never said anything about your 3G being bad either.

You implied the alternator cant run a blower motor without dropping voltage. I'm simply telling you that you have been led to the wrong conclusion based on incorrect diagnosis.
 

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Discussion Starter · #11 ·
And if you reread my posts, I never said anything about your 3G being bad either.

You implied the alternator cant run a blower motor without dropping voltage. I'm simply telling you that you have been led to the wrong conclusion based on incorrect diagnosis.
Sorry I worded it like that :doh0715: I am only trying to say that I have a problem with my blower motor or blower circuit. What I was implying is with this high output 3G 160 amp alt there is more than enough amperage to supply to the blower motor. If I had not let every one know what I have done then a old alt might be a problem. Hopes this is clear now.:beer
 

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Sorry I worded it like that :doh0715: I am only trying to say that I have a problem with my blower motor or blower circuit. What I was implying is with this high output 3G 160 amp alt there is more than enough amperage to supply to the blower motor. If I had not let every one know what I have done then a old alt might be a problem. Hopes this is clear now.:beer
Gotcha. The way to rule out the alternator is by measuring voltage at the battery. Quick and easy and we can move onto the other 2 things you mentioned...blower motor or blower circuit. Like you, I doubt its your alternator and am leaning toward blower circuit like a bad ground.
 

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Discussion Starter · #13 ·
Gotcha. The way to rule out the alternator is by measuring voltage at the battery. Quick and easy and we can move onto the other 2 things you mentioned...blower motor or blower circuit. Like you, I doubt its your alternator and am leaning toward blower circuit like a bad ground.
Ok here it is with all measurements taken at the battery with a fluke true rms digital multimeter.

With the bronco not running battery voltage is 12.46 volts.

With the engine running at idle 14.45 volts

With fan on low 14.41, next 14.38, next 14.36, high 14.33
I have 4 speed setings but my book only shows 3. EB Iam guessing.


Now taking voltage readings at the fan motor where the wires go into the motor.

I checked the voltage on the wire at the fan motor with it on high.

From the ground wire on the fan motor to battery positive 13.38 volts.

From the positive wire on the fan motor to battery negitive 12.22 volts.

from the fan motor positive wire to the fan motor negitive wire 11.28 volts.

The voltage gauge (stock) on my gauge cluster drops to around 13 volts enough you can see the movement on the gauge. So do I have a problem or not?

Thanks Mark
 

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Ok here it is with all measurements taken at the battery with a fluke true rms digital multimeter.

With the bronco not running battery voltage is 12.46 volts.

With the engine running at idle 14.45 volts

With fan on low 14.41, next 14.38, next 14.36, high 14.33
I have 4 speed setings but my book only shows 3. EB Iam guessing.


Now taking voltage readings at the fan motor where the wires go into the motor.

I checked the voltage on the wire at the fan motor with it on high.

From the ground wire on the fan motor to battery positive 13.38 volts.

From the positive wire on the fan motor to battery negitive 12.22 volts.

from the fan motor positive wire to the fan motor negitive wire 11.28 volts.

The voltage gauge (stock) on my gauge cluster drops to around 13 volts enough you can see the movement on the gauge. So do I have a problem or not?

Thanks Mark
Good measurements! Looks like you have at least a 1 volt drop on both the positive and negative sides of the blower, which adds up to reduce the voltage at the blower to 11.28.

Don't worry about what the dash gauge says, its too inexact to be of any use. You can try to trace the wires and clean any connections, but if it really bothers you, Id run new larger wires.
 
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