1996 Ford Ranger
2.3L, 4x2, 5spd


At the beginning of the winter, I lost the blower motor in my truck. The blower will currently not work on any speeds.



Here is what I have done to date:

1. Have checked both the fuses in the cab and the under the hood: all ok.
2. Have provided alternate power directly to the blower motor and it runs.
3. I replaced the switch in the cab.
4. I replaced the resistor and plug under the hood.
5. I replaced the relay behind the headlight.
6. A continuity check between the relay and the motor passed.
7. A continuity check from the fuse under the hood to the relay failed.
8. If I switch the fan from off to any other function, I can feel/hear the switch engage/disengage.

Despite all of this replacement and diagnostics, I cannot seem to find the issue. I am mostly confused as to why I can feel/hear the relay operate, but I did not have continuity from the fuse to the relay. After the continuity check, I assumed there was a wiring issue between the relay and the fuse box, but it doesn't make sense that the switch sounds like it is still working.


Any and all suggestions would be greatly appreciated!


Thanks.

 

I’d recommend re-testing the system as follows

Control Circuit:

1. With the Key on in run position, double check Fuse 6 (7.5 amp) in the dash fuse block and the Blower Motor Fuse located in the Power Distribution Box under hood (40 amp) with a voltmeter, checking both sides of the fuse to ensure its good.

2. If both fuse check good, pull the Blower Motor Relay from its socket. With the voltmeter set to read voltage, connect the Negative probe of the voltmeter to Chassis Ground. With the Key in the run position insert the Positive probe into terminal 2 of the relay socket (should coincide to a Black Wire with a LT Green stripe). You should read battery voltage. If not, then there is an open circuit between the fuse 6 and the relay.

3. If above checks good, with Key off, turn the Selector Switch to Panel (Dash Vent) or Defrost position. Set the voltmeter to Ohms. Connect the meters Negative probe to Chassis Ground. Insert the Positive probe into the Blower Motor Relay socket 1 (should coincide to a Red Wire with a Orange stripe). You should read less than .2 ohms or continuity. If not, there is an open circuit between the relay socket and the selector control switch or a bad ground at G102 (Not sure where G102 is located on a 1996).

Power Supply Circuit:

1. If all of the above checks good, with key off, set voltmeter to read volts. Connect the Negative probe to chassis ground and the Positive probe to the Blower Motor Relay socket terminal 5 (should coincide to a Black Wire with a Green stripe). Should read battery voltage. If not, there is an open circuit between the Blower Motor fuse and the relay.

2. If above checks good, set voltmeter to Ohms. Connect Positive probe to the Blower Motor Relay Socket terminal 3 (should coincide to a Pink Wire with a White stripe) and the Negative probe to the Blower Motor connector terminal 2 (should coincide to a Pink Wire with a White stripe). Should read less than .2 ohms or continuity. If not, there is an open circuit between the relay and the blower motor.

3. If above checks good, set the fan speed switch to max, and selector switch to Panel (dash vent) or defrost. Set the voltmeter to Ohms, connect the Positive probe to the Blower Motor connector terminal 1 (should coincide to a Orange Wire with a Black stripe). Connect the Negative Probe to Chassis Ground. Should read less than .2 ohms or continuity. If not, there is an open circuit between the Blower Motor, Selector Control, or G102.

 

Rev,


Thank you very much for the detailed reply. The only question I have at the moment is how do the socket numbers you indicate in your post correspond to the socket numbers on the relay (30, 87, 87a, etc.)? I cannot tell which colored wire corresponds to each socket.


Thanks!

 

The coil side, normally terminals 85 and 86, are interchangeable. They are not polarity sensitive unless a spiking diode is used. So there is no simple way to determine which corresponds to socket terminals 1 and 2 as used. Sometimes you may find the numbers are embossed on the socket either where the wiring enters or on the plug side.

The only sure way is to verify the wiring color. However, if the fuses and there associated wiring to the relay socket are good, you can back probe each terminal in the relay socket testing for power. With the Key off only one should have power (socket Terminal 5 / common relay terminal 30). This is from the Blower Motor Fuse (40 amp) in the PDB under hood. Make note of this terminal.

Next turn the key on and re-probe the socket. You should now find another terminal has power (socket terminal 2 common relay terminal 85 or 86). This is from fuse 6 in the dash fuse block. Make note of this terminal.

If you were able to determine the above two terminals you can try setting your meter to Ohms and connecting one lead to terminal 2 of the Blower Motors electrical connector (should coincide to a Pink Wire with a White stripe) and then using the other lead from your meter to probe the other two terminals in the socket. One should read less than .2 ohms or continuity. This will be terminal 3 of the relay socket (common relay terminal 87).

By process of elimination, the other remaining terminal in the relay socket will be terminal 1 (common relay terminal 85 or 86). This is the ground circuit for the relay coil.