This 1995 Infiniti J30 came in with multiple blower issues. The main culprit was a faulty blower motor and I show how to change it at this repair post. Once I had a working blower motor I found that the lower speeds did not work.
In doing this post I am addressing the concern that the blower motor is working fine on high speed but there is a problem with the lower speeds.
You will first need to remove the lower cover under the passenger side of the dash. A few phillip’s headed screws…
…and the cover will drop down.
For some reason I did not get pictures of actually testing the signals. Probably more interested in finishing the job at the time.
There are three wires that connect to the blower resistor.
The Yellow/Black wire connects to the blower motor and is the ground control wire for the blower motor. With the system not working and a good blower motor present there will be a nominal battery voltage present.
The Black wire is chassis ground and terminates at the left side of the instrument panel.
The Light Blue wire is the control signal from the a/c controls system.
In my testing on this wire I found these voltages present with the faulty blower resistor. Key and a/c system on. Black lead connected to a known good chassis ground. Red lead connected to the Light Blue wire.
1.33 volts on the lowest speed.
1.435 volts on speed two.
1.61 volts on speed three
.003 volts on high speed
I found these voltages with the new blower resistor.
2.56 volts on the lowest speed
2.71 volts on speed two
2.93 volts on speed three
0.00 volts on high speed
The voltage reading is not a result of power being supplied from the a/c controls to the blower resistor. Instead it is being out put by the resistor and the controls are applying a ground signal to it in a varying degree that lowers the voltage. I would suspect that the output from the terminal in the blower resistor would be a nominal 5 volts.
The three terminal connector on the blower resistor.
The aluminum rods are for cooling the resistor electronics. The resistor actually is not a resistor instead it is a power module or blower speed controller. The manufacturer describes it as a resistor so I have been doing the same.
The new and old resistor assemblies side by side.