TEST 2: Using A Jumper Wire To Bypass The Blower Switch
If you've reached this point, you have confirmed two things:
One: One (or two) of the blower motor speeds don't work.
Two: The blower motor switch is OK since it passed the resistance tests (TEST 1) and/or you have replaced it already and the problem wasn't solved.
The next step is to bypass the blower switch using a small jumper wire and indirectly test the wiring and blower resistor between the switch and the blower motor.
IMPORTANT: To avoid damaging the blower switch connector's female metal terminals you should use a small diameter wire as a jumper wire.
NOTE: All of the tests below require that the A/C Heater control panel vent knob NOT BE in the OFF position. In the OFF position, the ORG/BLK wire of the blower switch will NOT get power and this wire needs power for the tests to work. See the photo below to identify the vent control knob.
Alright, these are the test steps:
- 1
Disconnect the blower switch from its harness connector and turn the key to the on position (but no need to start the engine).
NOTE: All of the tests in this section are done on the blower switch's harness connector and not on the switch itself. The photo above shows the front view of the female metal terminals of the connector. - 2
Jumper terminals 2 and 3 together. This is the circuit that controls blower speed M1.
The correct test result is for the blower motor to run on M1 speed. - 3
Jumper terminals 2 and 4 together. This is the circuit that controls blower speed M2.
The correct test result is for the blower motor to run on M2 speed. - 4
Jumper terminals 2 and 1 together. This is the circuit that controls blower speed HI.
The correct test result is for the blower motor to run on HI speed.
Let's take a look at what your test results mean:
CASE 1: The blower motor failed to run in one of the jumper wire tests above. This tells you that that specific circuit is bad.
Although it's beyond the scope of this tutorial to test these circuits, you have eliminated the blower switch (on the A/C-Heater control panel) as bad. There's a good chance that you've got a bad blower motor resistor.
The blower resistor can be tested and the following diagnostic tutorial may be of help:
CASE 2: The blower motor ran when all of the indicated terminals were jumpered together. This tells you several important things:
- That the circuits between the resistor connector and the blower motor are OK.
- That the blower motor relay is OK.
No further testing is required of the blower resistor, the blower relay or the blower motor.
Where To Buy The Blower Switch And Save
You don't have to buy the whole A/C-Heater Control Panel to replace the blower control switch since the switch is removable. If you're interested in the original Ford Motorcraft blower switch or on an after-market part (and save), the following links will help you comparison shop.
The following links will help you comparison shop for the blower motor control switch and the connector:
Wondering if the above switches fit your particular Ford Explorer (Ranger)? Don't worry, once you get to the site, they'll make sure it fits by asking you the specifics of your vehicle. If they don't fit, they'll find you the right one.
More Ford 4.0L Tutorials
You can find a complete list of 4.0L Ford troubleshooting tutorials here: Ford 4.0L Index Of Articles.
Here's a sample of the tutorials you'll find in the index:
- How To Test The Fuel Pump (Ford 4.0L).
- How To Test Engine Compression (Ford 4.0L).
- How To Troubleshoot A No Start (Ford 4.0L).
- How To Test The Fuel Injectors (Ford 4.0L).
- How To Test The Ford EGR Valve EGR Vacuum Solenoid, DPFE Sensor (at: easyautodiagnostics.com).
- How To Test The Coil Pack (Ford 3.0L, 3.8L, 4.0L, 4.2L) (at: easyautodiagnostics.com).
If this info saved the day, buy me a beer!
