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Heater fan drains lots of current
#1
This might seem like a stupid question but I have no reference whatsoever, so I´ll give it a shot.
I just thought of something I witnessed last year before I stored the car for the winter.
When I was driving in the evening I had the top down and the heater on and the fan on full speed. I noticed that the power windows were going very slowly and saw that the voltmeter just under 11 volts instead of the usual 14,5.
Obviously the fan puts a lot of drag on the system as flipping the switch from position 1 to 3 will make the voltmeters needle jump back and forth.

Is that normal or is there too much resistance somewhere? Anyone else witness that on their cars?

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Mike

"If I were you...... I´d rather be me."  Tongue

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#2
Interesting. The heater fan is powered off of a 20 amp fuse (top right), so if it draws more than that, the fuse would blow. That's not enough current to draw voltage down that much.

You do have a fuse in there and didn't bypass it, eh?

My suspicion is on the power windows drawing down the voltage, as they take a butt-load of current.

Let me check your shorts!
http://midlifeharness.com

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#3
Thanks Midlife but I should have made a point that the windows were the reason I looked at the voltmeter in the first place.
Even when I don't touch the windows the fan on full speed reduces the current to under 11 volts.
Btw, using the windows will not even make the voltmeter shiver, let alone go down at all.
The three different positions of the the fan switch will cause three different readings on the voltmeter. The higher the fan speed the lower the volts.

Oh, about the fuse...... I guess there is one. I have only replaced one or two in the 14 years I've had the car. The fan one wasn't one of them, so I would have to check.

[Image: 1z21rv4.png]

Mike

"If I were you...... I´d rather be me."  Tongue

Check out my video:
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#4
If you have AC the current draw on your blower motor should be between 15 and 16 amps on high. If you just have a heater, the blower draw should be around 7 amps on high.
If the current draw is any higher than those values there are two possibilities, the blower motor has problems, or you have a high resistance connection someplace in the circuit. Where you have your voltmeter connected may give you a clue as to where the problem is. I would use a VOM and check the voltages at various points, including both sides of the fuse, to see if you can determine where the loss is taking place.
I would also make sure your alternator is providing adequate current and voltage.



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#5
Could it be the Heater Switch Resistor? Mike mentions that the different speed settings affect the voltmeter differently. If not that the heater motor may be going out.

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#6
No AC.
Ok. Thanks a lot guys. From what I gather this is not normal. I'll try and get my voltmeter and check it although electricity is just big voodoo for me. Smile

[Image: 1z21rv4.png]

Mike

"If I were you...... I´d rather be me."  Tongue

Check out my video:
http://www.7173mustangs.com/thread-my-mustang-in-action

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#7
Take a look at this, from Popular Mechanics, it has some good basic information.
http://www.popularmechanics.com/cars/how...6/4314662/



“If you can't explain it simply, you don't understand it well enough.”
--Albert Einstein
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#8
Basic battery/charging system voltages;

With the car NOT RUNNING battery voltage should 12-12.5v unless it has a surface charge from running the engine or a portable charger, a surface charge could be as much as 13/13.5v and the surface charge will dissapate in hours. Running any electrics will drop the voltage.

With the car RUNNING the charging system (Alt + Reg) SHOULD KEEP the battery voltage at near 13.7v no matter what is turned on. If the Battery voltage falls below 12v that is a discharge and in time the battery will be dead. If the voltage is near or over 14v the battery will cook and it's lifespan severely shortened.

Amazing how a loose altenator belt can effect the output at an idle, check the belt tension in that case.

Ugg I used to do these diagnostics for a living but it's been years.

Good Luck
Paul
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#9
Thanks Paul.
Everything works perfectly within normal thresholds, whether the car is idling or driving. Only the fan will make the voltage drop.
Just found out my voltmeter no longer works. Need to get me a new one, so this may take a while.
Thanks

[Image: 1z21rv4.png]

Mike

"If I were you...... I´d rather be me."  Tongue

Check out my video:
http://www.7173mustangs.com/thread-my-mustang-in-action

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