I wanted to let everyone know that I have resolved the front blower not operating while control still lights up. I had a particularly hard time isolating the cause because I WAS receiving 12v to the fan and it was not spinning until truck warmed up. I disassembled the motor and checked brushes along with resistor and everything seemed fine. It seemed that I needed a new blower since I was receiving voltage to the unit and I somehow had an intermittently operating fan. It turns out it was the relay. When the relay was energized it seemed to provide voltage but no amperage.

So dont assume a bad fan because you have voltage. It still provided power but not enough for the fan to spin. It did however have enough juice to power a test light and and diagnostic tool. I never swapped the relay because I assumed it was functioning due to it providing voltage to the unit when energized.

Hope this helps someone

John

 

We appreciate you telling us about that. I can believe that a relay would allow "volts" to show good but not allow amps to flow. It is kind of like when only one strand of a multi strand conductor is all there is. A no load voltage test will show OK as long as there is no attempt to put a load thru the conductor.

I recall once I had a power cube that showed 12VDC even when not plugged in to 120VAC. It also showed 12VDC when plugged into 120 VAC. It took me a long time to figure that out however - internal capacitor or something was holding a voltage but no current would flow.

I have a suspicion the relay problem you refer to is not unique and why LR recommends replacement of the original 70 amp relay, R7, when a new suspension air compressor is installed.

Now I wonder how you did figure out the problem was the relay - it is not what one would call common or obvious. Maybe we should start to anticipate relay problems as our 3's age.

DISCO3.CO.UK Photo Gallery - LR3 Air Suspension fuse 35P ECU Manual Shut Off Switch/Underhood Fuse and Relay Box drawing

 

It wasnt my electrical expertise that led me to it thats for sure! The fan started to run with the truck off, then I knew the relay was faulty. Swapped with rear air relay and works perfectly. My rear air has never worked which I am working on now with the thanks to wiring diagrams from unseenone.

 

That is almost funny - heater fan runs when engine off; will not function will engine on; typical LR.

That is almost like my power cube story - shows a voltage when not plugged in. Thanks for the update.

 

Hey oljohnboy! I am now in the thralls of this very issue and could use some help. I have a 2005 LR3 SE. Fan motor went off on it's own a couple times and then finally today stayed off. Haven't had anything from the rear for some time. I've seen several threads referencing the exchange of the relays, but for the life of me can't figure out where these relays are. Can you be as specific as possible as to their location and description. It would be greatly appreciated. Thanks!

 

Per the three jpg's below, relay R10 is for the rear fan and R16 for the front heater fan and circuits.


Incidentally each relay can be really hard to remove. I had to use pliers and a steady pull but not squeezing to tightly as to crack the relay plastic cover. If your R16 is like mine and the jpg, that is the relay to pull first as it is most accessible.

 

Thanks bbyer, I did finally figure it out yesterday. Tried swapping the two relays, with no result. Went to the local parts place and got another relay, but he didn't seem to confident that it was an exact replacement. Tried that for both motors, no result. Pulled another relay from the front headlight washer and tried on both motors, no result. Disconnected the control module/resistor on the front motor and tried the rear climate, no result. I checked the fuses inside and out, including the two link fuses, all good. So here's where I'm at. Rear climate wasn't working prior to the front having issues, so I don't know how one may tie in with the other. It can't be just a relay, because I know the one for the headlight washer is good. Is it possible that I have bad resistors on both motors? Are these two systems tied together somehow? Are there cabin filters that need to be cleaned out? Lastly, you may remember that a while back you helped me diagnose and air ride problem. After all the BS, it turned out to be a corroded wire joint. Any chance that's the issue here? Thanks!

 

I think it is time to slow down and figure out what works and what does not. Like the air suspension, trouble shooting is a long drawn out time consuming maddening process but ....

Perhaps start by reviewing the wiring diagrams again per the link below.

DISCO3.CO.UK Photo Gallery - Heater Air Conditioner System/LR3 Air Conditioning High Line electrical wiring diagrams

The rear fan circuit has a 30 amp fuse, F22E and the front fan circuit, a 40 amp fusible link, L12E. Some who can usually catch a blown fuse, have been fooled into thinking a fusible link is OK when it is not.

Also fan motors do burn out and quit independent of all else. That is why I suggest you start by figuring out if each fan motor will run by connecting 12 volt power and a ground directly to each fan motor connector.

Also your parts guy was correct in being cautious regarding relays. I suggest you order genuine as most LR relays contain a small resistor and diode to control back EMF caused by the make and break of the relay. This is to protect the computer circuits.

Files within below show the location of the pollen filter. When you purchase a new one, buy the charcoal filter, LR part number JKR500020 or Mann CUK2747. A plugged filter will not stop the fan motor but it will have to work harder and the system overall will not work too well either.

And yes, there is a pollen filter in the front heating system. Plugged it does not stop the fan motor but it makes it work harder and the system does not work well period.

DISCO3.CO.UK Photo Gallery - Heater Air Conditioner System

 

Sweet, your knowledge of these matters is a blessing, as always. I pulled the two fusible links and ohm tested them both. I assumed if they were bad, you would get an open circuit and no ohm reading, which did not happen. Is this correct or no? Also, after one day with no vehicle, I could wait no longer and did indeed hard wire the blower and it worked! I ran a 10 gauge lead, with a 30a inline fuse next to the battery, into the cabin to a 35a toggle. From there, it goes to the motor, which I grounded using a factory ground point near the door. Flipped the switch and voila! So, knowing the motor works and how to check and replace the cabin filter, what's next?

 

By the sound of your words, the fusible link and fuse are OK but to be clear, for a good fuse or link, on a digital ohm meter, you should be seeing a small ohm number on the display close to zero such as maybe from 1 to 5 ohms. In a good fuse and a fine setting, there will always be some resistance number. Try reading a number of brand new fuses as well to get an idea of normal.

If you see a - dash, or something like that or a really big number on the display, then the device is deemed "open circuit" and will not conduct electricity.

To be certain switch about the fuse or link with another that is probably OK and see if the other circuit still functions as it did.

I assume that was the front fan you got going. I guess if you can get a longer conductor, try the same on the rear fan. If both fans operate and the respective fusible links/fuses are OK, then I guess we are back to looking at the common elements which in this case is the heater control thing on the centre dash.

If so, I guess the first thing I would do is loosen the radio etc to get to the heater controls and then just unplug and plug back in the cables in the back of the heater controls.

I am still betting on it just being a power problem however. That is a lot more simple than any of this controls circuit board stuff. The good news is for the most part, the circuit boards are generally pretty good in our 3's and the problems are usually simple things like connectors, wires, and fuses. How LR manages that is beyond me.