OK, I will re-check the links under the hood again and do the swap to be sure. I'd like to go back to the resistor for the front motor for a moment. Would the intermittent function on the blower, and then no function at all, possibly indicate a bad resistor? This is the one piece of the puzzle I can't or don't know how to test and if I should order one, I want to get it going.

 

I would say that more often than not, the resistor is the problem.

The control system decides fan speed and the resistor is what translates the control signals into whatever makes the fan rotate slower - voltage, I guess.

The reason I ask about the rear system is to determine that the problems of the rear are not common with the problems of the front.

If they are unrelated, then replacing the resistor is a logical fix for the front.


Yes, Christmas is coming and no parts til 2015.

 

Just pulled the cabin filter and what a mess! So easy and so obvious, but I'm sure it's overlooked a lot. Just ordered a new one and will continue with diagnostics.

 

Ok, I've exhausted a lot of options, so this is where I'm at:
replaced the resistor with new one, no change
hooked everything back up and tested voltage at the motor. with the controls on high, i get just over 12 volts. that does not change at all, until i turn the control all the way down to the off position.
i know the relays, link fuses and resistor are good.
So, a couple of questions:
1. should i be looking at the fan switch in the display console?
2. how can i test the wiring coming to/from the resistor?
2. looking at the wiring diagram provided in the thread, i need a better understanding of the wiring between the control module and the blower. as far as i can tell, the only wire between the two appears to go from the module to the ground on the blower. how exactly does this control the speed on the blower??

 

I am back to asking about the fan again. I assume when 12 VDC from a battery is applied directly to it, that the fan appears to run full speed. I also assume you do not have a large old type rheostat such that you could apply a variable voltage to the fan.

You might try hooking the fan directly to 12 volt again and then with your fingers try to slow down the rotation of the fan blades - a bit tricky but the idea is to see how strong the fan motor is. I can envision that the fan will rotate at a pretty good speed but have no torque. No torque would indicate a fan problem.

You should be able to do the same re the rear fan and get near the same torque feel if both fans are OK.

Regarding your question of the fan speed switch, as best I can tell, the switch talks to the circuit board and the circuit board to the fan speed resistor and the resistor tells the fan how fast to rotate.

To tell how the circuit board reacts to a fan speed request change, you probably need a code reader and even then, the codes generated usually only provide for what I would call an educated guess.

In summary, try to compare the operation of the front fan with the rear fan when connected directly to a 12 VDC battery and see if they both seem to behave in the same manner, particularily with regards to torque.

 

Below is the LR explaination of how blower speed is controlled. This is taken from one of the pdf's in the linked files I referenced in a previous post.

The PWM, Pulse Width Modified signal referred to is not quite digital but may as well be as there is no practical way to measure it, or not.

That is why on the wiring diagram it looks like the voltage to ground is being controlled but it is not, however the fan voltage is being varied and the resistor, (blower control module), is sort of what does it after being instructed by the circuit board, (called the ATCM), using PWM type signals.

Blower Control

When A/C is selected or the blower speed is manually selected, the ATCM energizes the coil of the blower relay in the Battery Junction Box (BJB).

The energized blower relay supplies battery power to the blower motor, which is grounded through the blower control module.

The speed of the blower is controlled by a PWM signal from the ATCM to the blower control module. The blower control module regulates the blower motor voltage in relation to the PWM signal.

When the blower is in the automatic mode the ATCM determines the blower speed required from the comfort algorithms.

When the blower is in the manual mode, the ATCM operates the blower at one of seven fixed speeds as selected on the control panel.

 

Hello, I am in the middle of this exact problem (fan switch lights up as if blower was working but no air is moving, and cannot hear blower).


I have swapped blower relays from front to rear (R10 and R16, I believe) and had no change. Is there another relay to look for?

 

Below is a link to how to replace the blower motor and the "relay" that is really the fan speed control that is located right near the fan.

I replaced both fan and "relay" and got my system going again; also installed a brand new relay in the engine compartment as well - but yes, you found the only two conventional relays related to the fans - other than maybe checking a related fusible link - but the problem is probably the fan or what some call the blower resistor per the link.

https://landroverforums.com/forum/lr...e-relay-79499/

 

That link you provided is exactly what I was looking for, so thorough! I really appreciate you taking the time to explain everything and detail with Part Numbers. Very nice job.


I am going in for a closer look tomorrow morning. My Spidey sense is telling me it's the resistor module but we shall see.


Thanks again!

 

For me, the good news is it worked.

As to if the problem for me was the fan or the resistor relay, I never did figure that out.

The fan when I took it apart, had lots of black powder within the motor area, hence my feeling was replacing it was a good idea - also it was original so at least ten years old.

The blower resistor, when I took it apart, looked brand new.

If you want the aggravation of doing a job twice, you might first replace the fan, then if the problem persists, then the resistor.

At the same time, it seems for most people, the resistor is the solution, and the fan was OK.

For me, I was glad I replaced both and purchased a new engine compartment relay as well for good measure.

Thanks for the thanks above.