[ChadKirkwood]

Car is a 2007 second Gen xterra.

So like the post says. My blower fan had slowly been losing options, one didn’t work when we bought it then two went then three. Finally the blower motor just died.

So replaced the resistor, and blower motor. Only to have the fan work on only 4. I plugged the old resistor in and it works on 3 and four. The dealer says he “tested” the new resistor and it works as it should.

Next step by pass the switch to rule that out. Unplugged the switch and bridged between pins 4 and the pins for associated fan levels 1-3. Nothing on the new resistor but the old one runs on three same as the switch.

Im of the conclusion the new resistor is bad but the dealership is not. Anything else I can try short of getting a resistor from somewhere else.

I’ve searched the forum enough to know it should be the resistor, all of the fuses are still intact so I’m kind of at a loss.

Thanks

 

[XT2015]

Car is a 2007 second Gen xterra.

So like the post says. My blower fan had slowly been losing options, one didn’t work when we bought it then two went then three. Finally the blower motor just died.

So replaced the resistor, and blower motor. Only to have the fan work on only 4. I plugged the old resistor in and it works on 3 and four. The dealer says he “tested” the new resistor and it works as it should.

Next step by pass the switch to rule that out. Unplugged the switch and bridged between pins 4 and the pins for associated fan levels 1-3. Nothing on the new resistor but the old one runs on three same as the switch.

Im of the conclusion the new resistor is bad but the dealership is not. Anything else I can try short of getting a resistor from somewhere else.

I’ve searched the forum enough to know it should be the resistor, all of the fuses are still intact so I’m kind of at a loss.

Thanks

Factory Service Manuals - NICOclub
Page HAC-28 has the circuit diagram of the blower resistor detail in the blower motor detail.
Have you tested the resistor yourself with a multimeter to measure ohms of resistance from say 1 to 4; 2 to 4; 3 to 4? Should be reading some progressive resistance in one direction or the other. Looks like there is a fuseable link internal to the resistor pack.

 

[ChadKirkwood]

That’s what the parts guy at the dealer said he did, I’ll have to get a multimeter to test it myself. Not sure what it would be between the switch and the resistor though. One would think a bad connection would do the same thing with both resistors.

 

[XT2015]

That’s what the parts guy at the dealer said he did, I’ll have to get a multimeter to test it myself. Not sure what it would be between the switch and the resistor though. One would think a bad connection would do the same thing with both resistors.

Sounds like the fuse link in the "new" resistor is open and you only get full speed. With your old resistor I would expect you to find and open circuit between 2 and 3 that allows only 3 and 4 to be functional. The relay connects full voltage to the blower motor and the resistor connects that voltage to ground through different values of resistance determined by your resistor switch location. The resistor changes the current that is allowed to flow to ground and therefore through the motor regulating its speed.

 

[ChadKirkwood]

Alternator died last week so I’m in the process of fixing that before testing wires and things on the car. However, I did have a chance to test the resistor.

On 200 ohm on the old resistor I get .7 or .8ohm on one prong (I’m assuming fan speed 3) the others show nothing. Great we know that already.

on the new resistor I get nothing all the way across. I do however get readings on both 200k and 2m settings. My understanding of ohms is 2m and 200k is very little resistance while 200 is infinite.
So what do we think? Resistor isn’t providing enough resistance for the amount of amperage?

pics of resistor orientation and which prong is power for reference. Writing side up, clip side down, third prong from the left seems to be power in.

 

[ChadKirkwood]

Called my electrician friend and apparently I have my ohm readings backwards. That would mean the new resistor is providing a boatload of resistance compared to the old one

 

[MeToo]

The settings on the VOM just help with greater accuracy.

For readings that are going to be in the range of 0.5Ω to 18Ω, put it on the 20Ω setting.

Also, make sure that your "resistor" is not a digital PWM using a MOSFET unless that is what is needed. That is usually the kind used for Auto Climate Control and allows for around 16 fan speeds, whereas MCC has 3 speeds on the resistors, plus full voltage for High.

 

[ChadKirkwood]

The pwm is 2009+ I think right. The one with the tree fins on it. The one I have is the same part number as the one I pulled out. Just can’t understand why it won’t work.

 

[XT2015]

Alternator died last week so I’m in the process of fixing that before testing wires and things on the car. However, I did have a chance to test the resistor.

On 200 ohm on the old resistor I get .7 or .8ohm on one prong (I’m assuming fan speed 3) the others show nothing. Great we know that already.

on the new resistor I get nothing all the way across. I do however get readings on both 200k and 2m settings. My understanding of ohms is 2m and 200k is very little resistance while 200 is infinite.
So what do we think? Resistor isn’t providing enough resistance for the amount of amperage?

pics of resistor orientation and which prong is power for reference. Writing side up, clip side down, third prong from the left seems to be power in. View attachment 79583

What makes you think the terminal lead you are touching with the black negative probe is power In? Where is the red positive lead connected to?

 

[ChadKirkwood]

What makes you think the terminal lead you are touching with the black negative probe is power In? Where is the red positive lead connected to?

Touching that probe and any other one provides a reading on the multimeter any other combination of probes does not. At least on of those probes has to be power in the other three would be different fan speeds. That probe also has the thickest gauge wire coming into it if I remember correctly

 

[XT2015]

Touching that probe and any other one provides a reading on the multimeter any other combination of probes does not. At least on of those probes has to be power in the other three would be different fan speeds. That probe also has the thickest gauge wire coming into it if I remember correctly

What scale is the meter set on when you are getting readings? I can only imagine you are reading resistance in ohms since this resistor pack is not connected to anything but is isolated in your lap.

 

[ChadKirkwood]

What scale is the meter set on when you are getting readings? I can only imagine you are reading resistance in ohms since this resistor pack is not connected to anything but is isolated in your lap.

Correct the new one only shows resistance on the higher settings 200k and 2m ohms the old one shows up on lower settings. I think the new resistor isn’t just way to much resistance for some reason. Electrical stuff is not my forte however so I might be missing something

 

[MeToo]

There appears to be a little misunderstanding of how the resistor works.

When you test from any one terminal to any other terminal, there will be a reading. If there isn't, then either your meter is broken, the leads are broken, or the resistor is defective.

As I mentioned above, put the meter on the 20Ω setting, or maybe even the 2Ω setting, not 200Ω or higher.

 

[XT2015]

There appears to be a little misunderstanding of how the resistor works.

When you test from any one terminal to any other terminal, there will be a reading. If there isn't, then either your meter is broken, the leads are broken, or the resistor is defective.
View attachment 79593
As I mentioned above, put the meter on the 20Ω setting, or maybe even the 2Ω setting, not 200Ω or higher.

Great detailed info on the fan resistor pack. Trick is: Pin out numbering inside the actual connector is not sequential as might be inferred from the circuit diagram. Beware!