How to test the blower motor and resistor?

Bad89stang · 12-01-2003, 04:07 AM

My blower motor is drawing WAY too many volts from the system. The higher I turn the fan speed, the more it draws. I can get the voltmeter down to 10 at idle with the fan on high with a 130A alternator. Obviously, one of the two is bad.

Does anyone know a good test for either one? I have a Digital voltmeter so bring it on. I have the blower motor out right now, but it can easily be plugged in to run a test or two.

I am guessing the resistor is bad.

tmoss · 12-01-2003, 08:29 AM

Sound like the alternator to me - it should keep up with the stock fan no problem. Here is a diagram to help out with trouble shooting.............

Bad89stang · 12-01-2003, 10:28 AM

Thanks. The alternator is new and has been tested as good.

84LX89GT · 12-02-2003, 10:43 PM

On high the blower circuit bypasses the resistor (battery voltage to motor) and goes through stepped resistances through the resistor to obtain different speeds. How was the volume of air flow through your vents? A blower motor that draws alot of amperage usually is not working too good (extra resistance through motor) so it may draw alot of voltage. How much do your lights draw? Do you have pulleys? Do you ever have to jump start your car?

Bad89stang · 12-03-2003, 12:09 AM

Everything else works great. The motor blows very hard, but it was faulty. Plugged in a new one and it didn't even make the needle move on high.

84LX89GT · 12-03-2003, 10:44 PM

Cool, that's good to hear you figured it out. Just a hungry blower motor

12-01-2003, 04:07 AM	#1
Bad89stang Registered Member Join Date: Aug 2001 Location: Ft. Worth, TX Posts: 456	How to test the blower motor and resistor? My blower motor is drawing WAY too many volts from the system. The higher I turn the fan speed, the more it draws. I can get the voltmeter down to 10 at idle with the fan on high with a 130A alternator. Obviously, one of the two is bad. Does anyone know a good test for either one? I have a Digital voltmeter so bring it on. I have the blower motor out right now, but it can easily be plugged in to run a test or two. I am guessing the resistor is bad. __________________ You're gonna need your seatbelt

12-01-2003, 10:28 AM	#3
Bad89stang Registered Member Join Date: Aug 2001 Location: Ft. Worth, TX Posts: 456	Thanks. The alternator is new and has been tested as good. __________________ You're gonna need your seatbelt

12-02-2003, 10:43 PM	#4
84LX89GT Mustangs Join Date: Jul 2000 Posts: 1,938	On high the blower circuit bypasses the resistor (battery voltage to motor) and goes through stepped resistances through the resistor to obtain different speeds. How was the volume of air flow through your vents? A blower motor that draws alot of amperage usually is not working too good (extra resistance through motor) so it may draw alot of voltage. How much do your lights draw? Do you have pulleys? Do you ever have to jump start your car? __________________ 2005 Suzuki Hayabusa GSX1300-R 1980 Ford Thunderbird - 255 V8 ported heads, 5.0L ported stock headers, O.R. H-pipe and Flowmaster 2-chambers, dual roller timing chain hi-po Mack Truck hood emblem 1985 Mustang GT 5.0L T5, F-303, GT40p, headers, off-road h, flowmasters, MSD stuff, etc. Sold 02/06/04 1989 Mustang GT ET: 13.304@102.29 mph (5-24-03) Sold - 1998 Mustang Cobra coupe, 1/4 mile - street tires: 13.843@103.41 (bone stock)

12-03-2003, 12:09 AM	#5
Bad89stang Registered Member Join Date: Aug 2001 Location: Ft. Worth, TX Posts: 456	Everything else works great. The motor blows very hard, but it was faulty. Plugged in a new one and it didn't even make the needle move on high. __________________ You're gonna need your seatbelt

12-03-2003, 10:44 PM	#6
84LX89GT Mustangs Join Date: Jul 2000 Posts: 1,938	Cool, that's good to hear you figured it out. Just a hungry blower motor __________________ 2005 Suzuki Hayabusa GSX1300-R 1980 Ford Thunderbird - 255 V8 ported heads, 5.0L ported stock headers, O.R. H-pipe and Flowmaster 2-chambers, dual roller timing chain hi-po Mack Truck hood emblem 1985 Mustang GT 5.0L T5, F-303, GT40p, headers, off-road h, flowmasters, MSD stuff, etc. Sold 02/06/04 1989 Mustang GT ET: 13.304@102.29 mph (5-24-03) Sold - 1998 Mustang Cobra coupe, 1/4 mile - street tires: 13.843@103.41 (bone stock)