ac/heater blower not working, replaced resistor, still nothing
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Joined: Aug 2008
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From: Charleston, WV
ac/heater blower not working, replaced resistor, still nothing
A few days ago, my blower quit working on pos 1 & 2, but worked on pos 3 & 4. The next day, it briefly worked on all four pos. My buddy suggested replacing the blower motor resistor. NAPA gave me the wrong one, but in the process of trying to replace it, the blower doesn't work at all now. Went to the dealer today and replaced the resistor, but still nothing. I'm getting the green ac on light but the blower doesn't do anything.
Anyone have some test points that I could check some voltage. I also swapped relay R06 with R01 & R03. The truck would start & the high beams still work. I hate to replace the fan moter if something else is keeping it from working. The relays all nave the same part # so I'm assuming they are all the same. The 30a blower motor fuse is also good.
Anyone have some test points that I could check some voltage. I also swapped relay R06 with R01 & R03. The truck would start & the high beams still work. I hate to replace the fan moter if something else is keeping it from working. The relays all nave the same part # so I'm assuming they are all the same. The 30a blower motor fuse is also good.
Technical Article Contributor
Joined: Jun 2002
Posts: 10,511
Likes: 10
From: Under the flightpath of old ORD 22R
My assumption, 2004 Fx4, the FX4-Lux was not out then, so it is a EMTC HVAC unit.
Did you check any other fuses aside from F116 ?
The EMTC module is powered by F5 & F13. If you do not have power to the EMTC module, you cannot get a blower request to ground the front blower motor relay coil, to close the normally open contacts.
If you have the key in the run position, you should be able to change the HVAC output, and hear the panel mode actuator change. If not, the EMTC module is dead ( F5 or F13 ).
Use a meter and test for power on both sides of F13 & F5. F5 is hot at all times, F13 is only hot in the run position on the ign key.
If both fuses have power on both sides, next step is to pull the front blower motor relay, and jumper the Normally Open contacts.
The jumper positions is shown in the lower right hand corner, that is looking into the relay socket in the Central Junction Box
You need to pull the blower motor resistor and ground the Brown w/ White stripe wire in the blower motor resistor connector ( truck side ) to get ground to the blower motor.
This will test the blower motor on high, without the EMTC module in the path ( F5 & F13 )
Best to start with the panel mode actuator test by sound, then check the fuses
Did you check any other fuses aside from F116 ?
The EMTC module is powered by F5 & F13. If you do not have power to the EMTC module, you cannot get a blower request to ground the front blower motor relay coil, to close the normally open contacts.
If you have the key in the run position, you should be able to change the HVAC output, and hear the panel mode actuator change. If not, the EMTC module is dead ( F5 or F13 ).
Use a meter and test for power on both sides of F13 & F5. F5 is hot at all times, F13 is only hot in the run position on the ign key.
If both fuses have power on both sides, next step is to pull the front blower motor relay, and jumper the Normally Open contacts.
The jumper positions is shown in the lower right hand corner, that is looking into the relay socket in the Central Junction Box
You need to pull the blower motor resistor and ground the Brown w/ White stripe wire in the blower motor resistor connector ( truck side ) to get ground to the blower motor.
This will test the blower motor on high, without the EMTC module in the path ( F5 & F13 )
Best to start with the panel mode actuator test by sound, then check the fuses
Technical Article Contributor
Joined: Jun 2002
Posts: 10,511
Likes: 10
From: Under the flightpath of old ORD 22R
If you checked F5 & F13, and they were good, then the METC module has power, and should be able to change panel modes.
If you jumpered power as shown above, and grounded the other side, and the blower did not turn, it seems to be a problem with the blower motor.
That test was power to the blower, so it would run in high mode.
If you checked voltage on the back of the selector switch, and got different voltages, that is correct. The diagram above shows how a resistor is unsed inline with the blower motor to change the amount of voltage to the blower motor, to get it to run slower.
The selector switch was not involved when you jumpered the relay and grounded the other side of the motor ( at the same time, correct ? ).
Not sure why the blower motor is out now, but you can try to verify power at the blower motor connector.
Jumper the relay again, and ground the Brown w/ White stripe wire at the blower motor resistor, and at the blower motor you should get + DC volts.
The blower motor resistor can loose 1 or 2 of them. The 97-03 MY trucks would loose all but high when it went out.
If you jumpered power as shown above, and grounded the other side, and the blower did not turn, it seems to be a problem with the blower motor.
That test was power to the blower, so it would run in high mode.
If you checked voltage on the back of the selector switch, and got different voltages, that is correct. The diagram above shows how a resistor is unsed inline with the blower motor to change the amount of voltage to the blower motor, to get it to run slower.
The selector switch was not involved when you jumpered the relay and grounded the other side of the motor ( at the same time, correct ? ).
Not sure why the blower motor is out now, but you can try to verify power at the blower motor connector.
Jumper the relay again, and ground the Brown w/ White stripe wire at the blower motor resistor, and at the blower motor you should get + DC volts.
The blower motor resistor can loose 1 or 2 of them. The 97-03 MY trucks would loose all but high when it went out.