Today I had my first overheating issue. I'm from the denver area and never had a problem there, but sure enough the 110 degree weather in vegas has gotten to my disco. While rolling its fine, but once I come to a stop the gauge starts creeping up. The electric fans come on when I have the a/c on but shut off when I turn it off, even when it's overheating. From what I've seen on other cars these fans double as cooling and a/c fans, are they simply for the a/c on land rovers? Any ideas what might be causing the issue?

 

The a/c fans are supposed to stay on in a overheat situation, otherwise they are only for the a/c.
Start by replacing your fan clutch, check the tech section for the "how to" on this.

 

AC condenser fans come on for 3 reasons - (1) AC turned on, with interior fan on any position; (2) coolant temp at 212F, even if AC is off [this is determined by ECM and coolant sensor - which has two wires, vs the temp gauge sensor that has one wire]; and (3) fuel temp AND coolant temp above certain level, in which case an eight minute timer runs the fans to cool down the engine compartment after key turned off.

If overheat in slow traffic while you wreckless eyeball down the Vegas Strip, could be trash between condenser and main radiator - pull rubber strip to peek in there. Could be viscous fan clutch not engaging. With engine off, and approaching hot, fan should not free wheel, should turn less than 1 rpm when spun. With engine cold, fan should also be stiff to turn, and many make so much air move when first cranked in morning that you hear a "roar", which drops off in a minute or so. My new fan clutch moves enough air when cold to spin the AC fans even though they are off.

If overheat while moving at 40 mph, it is not the fan clutch. At either speed could be a clogged up radiator. Thermostats can stick open or closed, but that is not the slow process you described.

If I was in Vegas with my Disco, a long way from home, and over heating, I'd check coolant level when cold, radiator blocked for air flow, buy some water wetter at the auto parts store an add that to radiator (reduces temps quite a bit). You can get a radiator flushed fairly cheap or DIY with minimal tools. Fan clutch on the road - need a few more tools. But remember, fan is only an issue at low speeds. Thermostat is cheap, two bolts, and a pack of sealant.

My thought is the fan clutch, and if you don't want to deal with it on the road the watter wetter stuff will drop the temps a few degrees. You would be amazed at the trash that can get in between the condesner and rad and block the radiator.

If you want to deal with the clutch on the raod there are write ups on this forum for a $50 Chevy model, you have to enlarge the mount holes on the fan slightly.

As far as creeping up, you don't want to go above 50% on the guage. Save your gambler's luck for the tables. If you don't have a scanner with you, many auto parts stores will check codes for free or connect a scanner to demo it. Needs to be one that reads live data.

 

Is your Viscous clutch working? The large fan connected to the water pump. You should be able to hear it.

 

Hey Buzz, I knew when I was searching you'd be a contributor to helping me find my solution. Regardless, sorry to dig up and old thread. My fans work with A/C but will not function with temperature +212 degrees. Now that I have this valuable info regarding the coolant temperature sensor....I suppose I it's my non-genuine coolant temperature sensor causing my fans not to engage when my truck gets a little hot. What's everyone's thoughts?

I know this same sensor also distributes info to dash temperature gauge, that's working fine. Must not be transmitting to computer....

 

Two different sensors. One runs the analog gauge, one wire. The other, two wire, runs the ECU, and outputs to the OBDII as well (so you can get an Ultra Gauge for Fathers Day). One on the right is the two wire.

But the ECU uses a relay and fuse to control the fans:


M121).

The drawings are not real clear on the "ground" location the ECU uses, it may be internal, and has a parallel path that ground thru all the AC switch and blower control switch.

I'm not so sure mine still turns on without AC at 212. I would suppose on the trail, one could un-plug AC compressor and turn on AC to force fans on.

 

i have a similar problem. My fans won't come on at all. i have checked and the fans are ok. My temperature only climbs whe it is realy hot with the AC on. I will be watcing your thread for possible solutions. Good luck in Vegas!

 

Your the man Buzz! I had an Ultra Gauge and cracked the screen, it displayed temperature fine to the UG, so the CPU is getting the numbers....

 

I'm thinking that the ECU uses an internal ground to switch on that fan relay, rather than a series connection, so it could be possible that AC wiring is good, and turns on fans when they need it, but ECU has a bad transistor or what ever they use to control that point, and does not switch it on for just high temps. For me, seldom don't have AC on, so not a big point, but will probably look at changing ECU again.

 

I'm having a issue with my A/C fans too! They come on only for a few minutes when I start the truck (cold only) and thats it!!! I even wired my own circuit to them using the battery and it has 12.4 volts yet I get nothing. I know they work because otherwise they wouldn't come on at start up. I have checked fuses, and wires. I believe that the BLACK wire is the GROUND and the BLACK and BROWN wire is the POWER. I checked K5 in rave and didn't see it! Thanks in advance!