A/C blower in car not turning on?

LARRY HENDRICKS

MEMBER
2000 INFINITI I30
3.0L
6 CYL
AUTOMATIC
265,000 MILES

Recently my cooling fans threw a blade and wiped out the radiator. I installed new cooling fans, radiator, upper and lower hoses, new temperature sensor to turn on fans, 3 new radiator fan relays in relay box by battery. I also installed new cabin air filters as well. The new fans work well and coming on and off. The radiator is working great. Now my A/C compressor will turn on, but no blower motor comes on inside the car. I checked the two-blower motor 15-amp fuses in the fuse box under the hood by the battery, but they are fine. I have power to the blower motor relay under the dash as well. Both the wires going to the motor were tested with a test light and they are hot. I am stuck right now. Could it be the blower motor resistor or the motor? The A/C was working fine before I did the other repairs. Is it something I did or is this a coincidence? Help please!

Wednesday, August 2nd, 2023 AT 11:02 AM

1 Reply

STEVE W.

MECHANIC
14,683 POSTS

Okay, the "both wires to the blower are hot" isn't a good thing. You should have a white wire with a blue stripe and a blue wire with a white stripe. The white with blue is the power feed from the relay. Unplug the motor and connect your test light to terminal 1 in the harness side connector. Turn the key on, the light should come on. That shows that the relay is working and the wiring to the motor is okay. Now check terminal 2 (white with blue) It should not light up. If it does the most likely cause is a bad blower control amplifier aka resistor.
To test the blower motor simply jump battery voltage to the two terminals. Positive to terminal one and ground to terminal 2, if the blower spins up it's okay. Next connect the test light to battery positive and to terminal 2 in the blower connector harness side. Now turn on the key and slowly increase the blower speed. The test light should get brighter each increase. That circuit is designed to turn on the ground, it pulses it on and off to control the blower speed. To go one step farther you can unplug the connector to the resistor and use the test light connected to battery power to verify that terminal 3 in the resistor connector goes to a good ground. Then test terminal 2 for the control signal. First use the test light connected to ground.

Image (Click to make bigger)