Heater/Blower motor problem
- Thread starter DonMaximo
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HiFlow5 0
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Does the blower work when the selector is set to high only? If the blower works in the high only position then I would suspect the issue is the blower motor resistor. If there is no fan action in any setting then you more then likely have a wiring issue.
1. Check for open circuit voltage at the blower motor connector while unplugged, should read 12V. If not, then check wiring from switch to blower motor for breaks.
2. Check voltage drop across the motor while plugged in, should read 12V. If you get less then 12V while doing this test, then something in the circuit is using unwanted voltage. Next step would be to trace power and ground sides to see where the resistance is occurring.
Use this diagram as reference.
1. Check for open circuit voltage at the blower motor connector while unplugged, should read 12V. If not, then check wiring from switch to blower motor for breaks.
2. Check voltage drop across the motor while plugged in, should read 12V. If you get less then 12V while doing this test, then something in the circuit is using unwanted voltage. Next step would be to trace power and ground sides to see where the resistance is occurring.
Use this diagram as reference.
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I've noticed that the Selector switch (A/C, Vent, Heat, windshield defrost) is completely vacuum driven.
So, this led me to wonder if the blower will operate with the motor OFF, but the ignition switch in the ON/ACC mode.
In other words, should the fan blower work if the motor is Not Running ?
So, this led me to wonder if the blower will operate with the motor OFF, but the ignition switch in the ON/ACC mode.
In other words, should the fan blower work if the motor is Not Running ?
I don't think I followed ya, so take no offense.
The selector is vacuum actuated, but the motor itself is accessory powered. Thus it will not run with the key off (unless someone rewires it and sources battery power for the motor).
The selector is vacuum actuated, but the motor itself is accessory powered. Thus it will not run with the key off (unless someone rewires it and sources battery power for the motor).
Hissin-My apology, I can see where I was not clear.
Here's what I know:
- Jumped blower motor wires to fused line to battery and motor works
- all fuses are OK (passed)
- There is a 4 connector plug which connects to the "motor speed switch" (potentiometer),
Regardles of which Selector (vacuum operated) position is selected,
the 4 blower motor leads which go to the speed switch, never go HOT/positive.
** With ignition in ON or Access position
I would was expecting "some" voltage to 1 of the 4 connections.
I think I may need to seek out a dash wiring diagram. In one harness, there is a 2 wire plug that goes to the motor. And that 4 lead plug which goes to the motor speed switch. In the bowl of spaghetti, it's not simple weeding through this mess.
Again... any ideas, thoughts, or considerations appreciated !
Here's what I know:
- Jumped blower motor wires to fused line to battery and motor works
- all fuses are OK (passed)
- There is a 4 connector plug which connects to the "motor speed switch" (potentiometer),
Regardles of which Selector (vacuum operated) position is selected,
the 4 blower motor leads which go to the speed switch, never go HOT/positive.
** With ignition in ON or Access position
I would was expecting "some" voltage to 1 of the 4 connections.
I think I may need to seek out a dash wiring diagram. In one harness, there is a 2 wire plug that goes to the motor. And that 4 lead plug which goes to the motor speed switch. In the bowl of spaghetti, it's not simple weeding through this mess.
Again... any ideas, thoughts, or considerations appreciated !
Make sure the batteries in your DVM or multimeter are good before you start the troubleshooting process.
If you check out the diagram, you will notice that the blower has power anytime the ignition switch is in Run and the selector switch is in some position other than off. This uses current sink wiring, in that the device is always has power and the control part of the circuit provides a ground. No ground, no run. In automotive circuits, the ground is the return path for the power to get back to the battery.
Look for 12 volts at the brown wire on the blower motor with the ignition switch in Run and the selector switch is in some position other than off. No 12 volts: then the fuse, the wiring that feeds the selector switch or the selector switch is bad. Good 12 volts, then ground the other side of the motor: if the motor is good it will run.
Good 12 volts and the motor runs: the problem is in the wiring to the resistor assembly, the speed switch or missing ground between the speed switch and the car body. Turn the ignition switch to off, set the selector in center position. Set your DVM or multimeter to Ohms, choose the lowest range. Then check the resistance between the black wire on the switch and bare metal on the car body. You should see less than 1 Ohm. More that 1 Ohm means you have a bad connection.
Post your results and if you didn't find anything out of spec, I will post more troubleshooting steps.
If you check out the diagram, you will notice that the blower has power anytime the ignition switch is in Run and the selector switch is in some position other than off. This uses current sink wiring, in that the device is always has power and the control part of the circuit provides a ground. No ground, no run. In automotive circuits, the ground is the return path for the power to get back to the battery.
Look for 12 volts at the brown wire on the blower motor with the ignition switch in Run and the selector switch is in some position other than off. No 12 volts: then the fuse, the wiring that feeds the selector switch or the selector switch is bad. Good 12 volts, then ground the other side of the motor: if the motor is good it will run.
Good 12 volts and the motor runs: the problem is in the wiring to the resistor assembly, the speed switch or missing ground between the speed switch and the car body. Turn the ignition switch to off, set the selector in center position. Set your DVM or multimeter to Ohms, choose the lowest range. Then check the resistance between the black wire on the switch and bare metal on the car body. You should see less than 1 Ohm. More that 1 Ohm means you have a bad connection.
Post your results and if you didn't find anything out of spec, I will post more troubleshooting steps.
I am having the exact symptoms you had with your blower motor. I hot wired the blower and it works, the fuse is good and I have power going into the vacuum selection (panel, off, floor, defrost, mix) switch but no power at the speed switch plug or at the motor plug. What did you determine was your problem? I suspect there may be a problem in between the selection switch to the speed switch as its probably an internal connection in that part that is the problem
