Like the title says, replaced the blower motor resistor with the new and improved longer finned resistor and wiring kit. Made sure to switch the wires going to the blower and plugged it all back together. Still cuts in and out but seems once the Jeep is to operating temperature the blower is more consistent. Fuse seems alright, figured the only thing left could be the blower motor itself? Anyone else have this problem?
Replaced the Blower motor resistor with the new and improved one. Still problems
JGC99
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Like the title says, replaced the blower motor resistor with the new and improved longer finned resistor and wiring kit. Made sure to switch the wires going to the blower and plugged it all back together. Still cuts in and out but seems once the Jeep is to operating temperature the blower is more consistent. Fuse seems alright, figured the only thing left could be the blower motor itself? Anyone else have this problem?
It's like it keeps losing and getting power. If it's on full blast, it'll blast high speed then almost done to nothing then back up to high speed again and then no blower for a few seconds and back again. This is just an example of what it does, there is no pattern or anything it doesn't seem. I haven't pulled it out yet, but will need to. Don't know what that might get me though other than visually seeing the fan step on and off again.
The resistor is a passive component - it just sits there and turns electricity into heat. You can measure it with your multimeter - it should read a constant resistance, like 10 or 20 ohms. It's a crude way to control the motor speed, but it's ok here because your only purpose is to generate heat, and any heat from the resistor can be dumped back into the cabin air.
The first thing I'd try is to set the motor on the bench and try running it with a battery. Adding a fuse inline with the circuit would be a good idea. Check the wiring diagram to make sure that it's supposed to run at a full 12V battery power - pretty sure it should. If it runs ok, then put the resistor in series and see how much the motor slows down.
If the motor runs ok on the bench, and runs slower with the resistor in series, then I'd suspect the controls ... ie the heater switch.
The first thing I'd try is to set the motor on the bench and try running it with a battery. Adding a fuse inline with the circuit would be a good idea. Check the wiring diagram to make sure that it's supposed to run at a full 12V battery power - pretty sure it should. If it runs ok, then put the resistor in series and see how much the motor slows down.
If the motor runs ok on the bench, and runs slower with the resistor in series, then I'd suspect the controls ... ie the heater switch.
Ok that sounds like a good plan of action. It acts like off and then on, on and off back and forth for different lengths of time.
Where can I find a wiring diagram? I suppose they are in the FSM and I don't have one yet. I need to find a place to get one, anyone have recommendations?
Where can I find a wiring diagram? I suppose they are in the FSM and I don't have one yet. I need to find a place to get one, anyone have recommendations?
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Resistors are not generally intermittant. Good or 'open' (infinity on a VOM). I'd tend to think that it's the motor (yes, put it on a 'bench' and feed it 12 VDC). If it works OK, then go for switches, next. Generally, mechanical things die before electrical things. The fan is both! I can check the FSM tomorrow.
Took the blower motor out and hooked it directly to the battery. Spun freely. Has .4 ohm resistance. Tried checking the voltage to the blower motor. With the engine running, a contant 13.some volts, 12.some without the engine running. No peaks like I thought it would. Also when turning the knob to select blower speed, I didn't see any change in voltage, which I would expect. Otherwise, how does it control the speed of the motor, I assumed cutting voltage to make it slower. Need some help here. Could it be the panel that you control the speed with, HVAC assembly? Again, I have the new blower motor resistor and wiring kit installed.
Speaking generally, not from experience with this car, the blower motor resistor goes in series with the motor to lower the motor speed. There will be a voltage drop across the resistor in proportion to the current (Ohm's law) and the motor will see a lower voltage. The motor will spin slower at a lower voltage.
If you are looking at the voltage from the switch without a load, you are measuring an open circuit. When the circuit is open and no current flows, there is no voltage drop (again Herr Professor Doctor Ohm is in command). Put the motor in as a load and you should see different voltages.
If you are looking at the voltage from the switch without a load, you are measuring an open circuit. When the circuit is open and no current flows, there is no voltage drop (again Herr Professor Doctor Ohm is in command). Put the motor in as a load and you should see different voltages.
I'd guess 1/3 to 1/2 of what the fuse is rated. You can put your multimeter in series with the motor to measure the amps. most multimeters will measure up to 10 A or so. There will be a different way to connect the multimeter for measuring current - the current will go through the meter shunt (inside the meter) and the meter will display the internal voltage drop as a current.
I used a clamp on current meter, and got 13-14 amps going into the resistor at full bore. Fuse is a 40 amp I believe. Something isn't coming together right, why does it still cut in and out? Unless I needed to check the current from the blower motor to the resistor itself
At this point I would scope the power to the motor - but likely you don't own an oscilloscope.
Your multimeter may be fast enough to keep up with the cutting in and cutting out ... if you measure the voltage across the speed resistor while the action is happening, that will give you more of an idea of what's going on in real time. You can alternately place a low-value resistor in series with the motor (in the single ohms range - a fraction of what the heater speed resistor measures - mind the power rating) and measure the current going through the motor from the voltage drop across this resistor. Again, Herr Professor Doctor Ohm is your friend here. An inexpensive analog voltmeter can be useful in situations like this, ie a Triplett meter or any old analog VOM (pre-multimeter).
I do not have the schematic in front of me - but as a WAG, I would guess that there is some kind of thermostatic protection for the motor, switch or resistor that is cycling on and off.
I would keep trying to collect data points by measuring every aspect of the circuit that I could. Measuring more costs you nothing, and may provide the insight that you need.
Your multimeter may be fast enough to keep up with the cutting in and cutting out ... if you measure the voltage across the speed resistor while the action is happening, that will give you more of an idea of what's going on in real time. You can alternately place a low-value resistor in series with the motor (in the single ohms range - a fraction of what the heater speed resistor measures - mind the power rating) and measure the current going through the motor from the voltage drop across this resistor. Again, Herr Professor Doctor Ohm is your friend here. An inexpensive analog voltmeter can be useful in situations like this, ie a Triplett meter or any old analog VOM (pre-multimeter).
I do not have the schematic in front of me - but as a WAG, I would guess that there is some kind of thermostatic protection for the motor, switch or resistor that is cycling on and off.
I would keep trying to collect data points by measuring every aspect of the circuit that I could. Measuring more costs you nothing, and may provide the insight that you need.
I work in a test lab so we do actually have o-scopes. I am not all that familiar with it yet, and have been using our Fluke DMM and amp clamp to check voltage and current.
So what your saying is get a single ohm resistor with a power rating of what like 150 Watts then, and then measuring the voltage drop across that resistor in series? That will show me fluctuations in voltage, but ultimately that is then either a faulty blower motor or the hvac control then correct?
So what your saying is get a single ohm resistor with a power rating of what like 150 Watts then, and then measuring the voltage drop across that resistor in series? That will show me fluctuations in voltage, but ultimately that is then either a faulty blower motor or the hvac control then correct?
Yep. P=IV=I^2R, so an ohm at 12A will be about 150W. So that's not really practical for most people ... sorry. You can go lower with the resistance, and have less PD (power dissipation). Low resistances are very hard to measure accurately though. A coil of wire may be enough resistance to see a voltage fluctuation. You won't know exactly what the current fluctuation will be, but it would show you the fluctuation in real time.
But I'd measure the voltage in real time across the existing circuit elements first. Measuring directly from the motor leads to ground should be ok, unless the back EMF from the motor goofs up the meter. I would put an inductor in series with the meter to filter out junk from the motor, but that's getting complicated. If you follow that and have an rf choke on hand, you could try it.
Might be better to start as far away from the motor as you can, and look for where the voltage fluctuations originate. With a VOM, you should see the voltage going up and down and then you can isolate where the switching is going on.
Have you tried connecting the Fluke meter to the runing motor and ground while the fluctuations are happening? Your typical digital multimeter (DMM) time-averages a DC signal, so the averaging may not be fast enough to detect the voltage changes. But you should be able to see that the voltage is fluctuating by watching the display jump around. Not accurate but telling. Fluke meters are great and very very tough, and there is a lot you can do with them.
Really the only thing I tried thus far was seeing what the voltage was coming out of the resistor and into the blower motor without the blower hooked up. As we talked about earlier, that really didn't get me anywhere as I had no load connected to it. The only other thing I checked was the current draw from the hvac panel to the resistor which was about 14 amps full bore if I remember correctly.
Next, I plan on measuring the voltage across the resistor. I should be able to do this by having one probe on on side of the resistor and the other on the blower motor side correct?
Following that, I am going to have the leads extended for the blower motor and measure the live voltage as I turn the knob up and down to see what the voltage drop is with differing speeds of the blower motor. Hopefully I'll also be able to catch a time or two when the motor itself has shut off.
Any other advice. This seems to be pointing to a faulty hvac panel it seems to me. Really there are only three things in question; the panel, the resistor or the blower motor. Resistor is new along with the wiring.
Next, I plan on measuring the voltage across the resistor. I should be able to do this by having one probe on on side of the resistor and the other on the blower motor side correct?
Following that, I am going to have the leads extended for the blower motor and measure the live voltage as I turn the knob up and down to see what the voltage drop is with differing speeds of the blower motor. Hopefully I'll also be able to catch a time or two when the motor itself has shut off.
Any other advice. This seems to be pointing to a faulty hvac panel it seems to me. Really there are only three things in question; the panel, the resistor or the blower motor. Resistor is new along with the wiring.
Well, you can measure the voltage drop across the component (not always useful), or you can measure the voltage from the component to ground.
Usually the value you want to measure is from the component to ground (your reference level).
I would let the motor run and start measuring the voltage to ground at the points I could easily reach. I would be lookign for the voltage fluctuation, ie if it is present or not. If my DMM display were not bouncing around, I would assume that the voltage is not fluctuating. I would prefer to start from the power input and move toward the motor, but only because that would be easier to think about in terms of localizing the problem. Divide and conquer! Good luck!
Usually the value you want to measure is from the component to ground (your reference level).
I would let the motor run and start measuring the voltage to ground at the points I could easily reach. I would be lookign for the voltage fluctuation, ie if it is present or not. If my DMM display were not bouncing around, I would assume that the voltage is not fluctuating. I would prefer to start from the power input and move toward the motor, but only because that would be easier to think about in terms of localizing the problem. Divide and conquer! Good luck!
So I did this on the way home from work and then at my place. First I hooked up the DMM to the leads coming from the resistor to the blower motor. That you can see fluctuate once the blower goes off, it shows OL (overload) then back to normal 12-13 volts to the blower motor.
This video shows the voltages the motor sees at different input levels, ie. low medium and high.
Then once home, I connected the DMM to where the leads go into the blower motor, more than likely from the hvac panel. Here the motor goes on and off around 1:13 in the video and you can hear it. The voltage drop is minimum and stays constantly close to 13 volts.
So did I get a bad new resistor then? Sure seems like the issue is within the resistor, doesn't it?
This video shows the voltages the motor sees at different input levels, ie. low medium and high.
Then once home, I connected the DMM to where the leads go into the blower motor, more than likely from the hvac panel. Here the motor goes on and off around 1:13 in the video and you can hear it. The voltage drop is minimum and stays constantly close to 13 volts.
So did I get a bad new resistor then? Sure seems like the issue is within the resistor, doesn't it?
What does this resistor look like? A true resistor is a very simple component - in this case, likely a nichrome wire around a former - and unlikely to fail in this manner. Either they work, or they go open. Very seldom resistors intermittently go open when they overheat, then test ok when they are cool.
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