Huge Current Drain (Blower Motor)

dcs7941

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Nov 20, 2005

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Georgia

Aug 2, 2006

#1

• Aug 2, 2006

• #1

I have a 95 Mustang GT with a 200 amp alternator and 4 gauge cable upgrade. When I turn on the blower for my Air Conditioner the anmeter will begin to drop from the M in NORMAL to R then O. I have an aftermarket stereo but this only happens when I turn on the blower. The higher the speed of the blower the greater the drain. Nothing else including lights, stereo, AC or cooling fan causes the voltage to drop. I can drive around in stop and go traffic and the reading stays on the M in NORMAL as long as the blower motor is off or at the lowest setting. Does anyone have any idea how to resolve this problem. Thanks in advance for your help.

 

HISSIN50

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Aug 2, 2006

#2

• Aug 2, 2006

• #2

The blower motor draws a good amount of juice. Do you have a real voltmeter that you can reference (your stock gauge is a voltmeter, not an ammeter. A portable ammeter would be nice for your testing of the blower motor though)?

Does the voltmeter drop even if you put the blower motor on the first two settings?

I doubt the wiring is bad but the motor might be on the outs. I kinda doubt it though.

Good luck.

 

badstang123

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Jan 17, 2006

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Aug 2, 2006

#3

• Aug 2, 2006

• #3

I have a digital voltmeter in my car and once I hit the thrid and fourth click the voltage begins to drop on mine as well. And that is with a 200 amp alternator and 1/0 Awg wiring

 

badstang123

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#4

• Aug 2, 2006

• #4

Also, the stock volt gauge is extremely inaccurate. In my car with the same voltage the needle will sit in different spots on different days. It's weird, but I don't trust the thing at all.

 

HISSIN50

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#5

• Aug 2, 2006

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I just re-read this. I think that's normal. You noted it happens with the AC on. When you turn AC on, you have the blower motor, the AC clutch circuit and the E-fan all running.

The test for the blower motor is to start with an engine and HVAC that are off (the E-fan continues to run after you turn the AC off, which can make this test invalid otherwise). Turn the HVAC to vent and turn on the blower motor. NOw you're just running the blower motor (no e-fan and no AC). If the volts dont drop as much, I think you're fine. Cool?

Justin, I aint about to comment on yours - I think I recall a sick stereo set-up with two batteries (I think), etc.

 

badstang123

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#6

• Aug 2, 2006

• #6

HISSIN50 said:

Justin, I aint about to comment on yours - I think I recall a sick stereo set-up with two batteries (I think), etc.

Click to expand...

You don't think that affects anything do you

 

dcs7941

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Nov 20, 2005

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Georgia

Aug 3, 2006

#7

• Aug 3, 2006

• #7

HISSIN50
As I increase the speed of the blower motor from position 1 to 4, the voltage drop increases. It is good to know that some of you have similiar problems. Sometimes I think the quality of the wiring used by Ford could have been better. However, I will try the test you mentioned in the previous post. Thanks for the response.

badstang123
Thanks for your input and comments.

 

dcs7941

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Nov 20, 2005

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Georgia

Aug 11, 2006

#8

• Aug 11, 2006

• #8

HISSIN50 said:

I just re-read this. I think that's normal. You noted it happens with the AC on. When you turn AC on, you have the blower motor, the AC clutch circuit and the E-fan all running.

The test for the blower motor is to start with an engine and HVAC that are off (the E-fan continues to run after you turn the AC off, which can make this test invalid otherwise). Turn the HVAC to vent and turn on the blower motor. NOw you're just running the blower motor (no e-fan and no AC). If the volts dont drop as much, I think you're fine. Cool?

Justin, I aint about to comment on yours - I think I recall a sick stereo set-up with two batteries (I think), etc.

Click to expand...

Here are results from my test:

Normal operation at idle = 14.38 Volts and 19 Amps
AC Speed 1 = 14.32 Volts and 37 Amps
AC Speed 2 = 14.31 Volts and 39 Amps
AC Speed 3 = 14.28 Volts and 42 Amps
AC Speed 4 = 14.25 Volts and 50 Amps

I also turned the blower on speed 4 with the vent only and no electric fan or ac. The current drain was 37 Amps for the blower on speed 4. Let me know if this sounds correct. Thanks!

 

HISSIN50

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#9

• Aug 11, 2006

• #9

Refresh my memory - the HVAC blower only has a 30 amp fuse/CB (I think it's a fuse, but a CB makes more sense, generally speaking).

Are those values you posted the amperage draw of just the HVAC motor (tested with a clamp-on meter, etc)?

If so, those values seem a bit high to me. Your values sound more like what an E-fan draws once it's up to speed. What amperage fuse is in the box (in case someone replaced it with a higher rated fuse)?