Blower motor draw

[Lax]

Here is a question for everyone. Could the blower motor on my cab heater draw so much power it puts my ampmeter into the yellow? My ampmeter was always squarely in the green until I got my cab heater going. Now with the engine running at idle when I turn the cab heater on the ampmeter jumps to the yellow and stays there. The longer I run the heater at highway RPMs the lower the ampmeter goes.

Is it possible that the blower motor can draw that much power? Does that mean a bad motor? How can I fix this? I can't have the blower motor drawing that much power for very long. The longer I run the blower the more power I am using. This is bad in 15 degree weather. Thanks for your help!

 

[jwaller]

in short, NO. you have either a blower motor with a big problem or an alternator thats not making much of any juice. I imagine that if your blower is pulling enough juice to do that then so would running the head lights. you most lilkly have a problem with the motor. when you run it for long enough to pull the voltmeter down is the motor hot to the touch?

 

[Lax]

Thanks guys. I do have a hand held volt meter. My question is what should the meter read and where should I check? I'm guessing right at the connections. Sorry for the silly questions. This is new to me and the truck was working great until this happened and now I can't drive it for more then an a couple hours because it draws the batteries down.

I always run with my lights on and the amp meter is always well into the green with no problem before. I can't believe that the blower motor could draw that much power but it sounds like that maybe it is. I appreciate any answers to the above questions.

 

[rwelker]

blower motor draw

It could be where you are drawing current from. Perhaps the circuit you tapped from is too light and affecting the volt meter. I would temporarily direct wire to the battery and watch the volt meter then. If it still drops then you have a problem. I had a batch of bad heater motors (brand new ones) on the truck I use regularly in the winter. I finally crossed over to a 24 volt motor from NAPA and no more problems. It has lasted 2 seasons so far; the military ones lasted about 6 hours each. If I remember correctly they draw about 6-8 amps on high; 3-4 amps on low.

 

[OPCOM]

RE: blower motor draw

not to dispute but with the engine running and the alternator working, the voltage should be close to 27.5 volts. If you have the 60 amp alternator, this voltage should hold with all accessories running, and should not drop below 27 volts. It is possible there could be a bad connection between the alternator and the electrical system that could cause an excessive voltage drop. If you can find a 0.1 ohm resistor and place it in series with the blower motor's hot lead, and measure the voltage across it, you can calculate the current draw from the measured voltage. The meter will indicate 0.1 volt for every amp of current drawn. 1 volt=10 amps.