lynall Posted September 23, 2007 Share Posted September 23, 2007 Just noticed the other day when i start my engine the air con fan is running permanently. with the climate set to off ie no air con or internal fan running, only runs with engine running Not sure how long its been doing this but as i drive with windows up it may have been for ages! Coolant level is spot on Coolant is circulating Gauge reads normal Sender okay with multimeter set to ohms according to rave specs Relay okay swapped with one next to it, when pulled fan stops so its getting a signal from somewhere possibly the ecu? Ta Lynall Quote Link to comment Share on other sites More sharing options...
BogMonster Posted September 23, 2007 Share Posted September 23, 2007 From the electrical library it would appear to be ECU controlled as you suggest: "Cooling Fan Description The cooling fan is located on brackets forward of the radiator. The fan motor is operated by a cooling fan relay controlled by the Engine Control Module (ECM). The main relay supplies a feed to the coil of the cooling fan relay. A permanent feed is supplied to the coils of the main and cooling fan relays located in the engine compartment fusebox. On V8 models a coolant temperature sensor is located in the inlet manifold, on Td5 models the sensor is located in the outlet housing. The ECM controls the operation of the main and cooling fan relays. At a preset temperature the ECM receives an input from a coolant temperature sensor above the values stored in the ECM. The ECM logic enables the earth path for the coil of the cooling fan relay. The fan motor then gets a feed from the closed contacts of the cooling fan relay. When the engine temperature falls, the sensor gives an input below the values stored in the ECM. When the input from the coolant temperature sensor is low, the ECM interrupts the earth path to the coil of the cooling fan relay. The contacts of the cooling fan relay open, this action breaks the feed to the cooling fan motor, and the motor stops. The cycle will start again when the engine coolant temperature rises and the sensor sends a high input to the ECM. The ECM has an engine off function, when the ignition is turned off the ECM logic goes into a watchdog routine and monitors the coolant temperature for approximately seven to ten seconds. If the coolant temperature is still high, over 100 C (212 F) V8, 110 C (230 F) Td5, the ECM logic can control the operation of the fan motor. On V8 engines the ECM will only enable the fan if the inlet air temperature is over 60 C (140 F). The ECM will allow the fan to run for a maximum of ten minutes, however the ECM continues to monitor the coolant temperature. The ECM logic will stop the fan if the coolant temperature is below the acceptable values stored in the ECM. To prevent a flat battery, the fan will be stopped (regardless of coolant temperature) if the battery voltage falls to 12 V. Cooling Fan Supply Circuit supply A permanent feed from the battery positive terminal is connected by an R wire to the engine compartment fusebox. A feed from this wire is connected to the contacts of the main relay and also to fuse 13. The feed passes through fuse 13 and to the inertia switch on a NB wire. The feed from the inertia switch flows on a WG wire to the engine compartment fusebox and is connected to the coils of the main relay. in this condition the coil and contacts of the main relay receive a permanent supply. The permanent feed from the battery on a R wire to the engine compartment fusebox is also connected via fusible link 1 to fuse 5. From fuse 5 the permanent feed is connected to the contacts on the cooling fan relay. In this condition the contacts of the fan relay receives a permanent feed from the battery via fuse 5. Main relay - ignition supply When the ignition switch is a position II, the ECM switches on the earth path for coil of the main relay. Current flows through the coil of the main relay and flows on a UR wire to pin C0635-23 V8/C0658-21 Td5 on the ECM. With the coil of the main relay energised the main relay contacts close, power is now available to the coil of the cooling fan relay, via the closed contacts of the main relay. Cooling Fan Operation V8 engine The engine coolant temperature sensor sends an input on a G wire to pin C0636-22 on the ECM. The engine coolant temperature sensor is earthed on a RB wire to pin C0636-21 on the ECM. When the coolant temperature is high, the value of input from the coolant temperature sensor causes the ECM logic to switch on the earth path for the coil of the cooling relay, on a GW wire to pin C0636-31 on the ECM. With the coil of the cooling relay earthed the coil is now energised. The cooling relay contacts close and current flows on a BN wire to the cooling fan motor. Td5 engine The engine coolant temperature sensor sends an input on a KG wire to pin C0158-7 on the ECM. The engine coolant temperature sensor is earthed on a KB wire to pin C0158-18 on the ECM. When the coolant temperature is high, the value of input from the coolant temperature sensor causes the ECM logic to switch on the earth path for the coil of the cooling relay, on a BP wire to pin C0658-4 on the ECM. With the coil of the cooling relay earthed the coil is now energised. The cooling relay contacts close and current flows on a BN wire to the cooling fan motor. All models The current flows through the cooling fan motor to earth header C0018 on a B wire. The cooling fan motor will operate as long as the ECM receives a high signal input from the coolant temperature sensor. When the coolant temperature is low, the ECM logic interrupts the earth path to the coil of the cooling relay. The contacts of the cooling fan relay open, the fan motor power supply is now broken and the motor stops. The cooling fan will cycle on and off as the coolant temperature rises and falls." Quote Link to comment Share on other sites More sharing options...
lynall Posted September 23, 2007 Author Share Posted September 23, 2007 Today using a power probe i have sussed that the relay is getting an earth from the engine ecm (ecu) so causing the fan to run. But i cant suss what is causing the ecu to think the fan needs to run1 I have done a check on the climate ecu and it shows no faults. The coolant fan relay is getting an earth signal but not the air con pump relay so i am pretty sure the signal is from the engine ecu and not the climate ecu. Rave tells me if the coolant temp sensor fails the ecu will work out the temp from the fuel temp sensor as a back up. Which is a bit of a tosser as i am not sure what is at fault the ecu or a sensor telling the ecu to run the fan. Lynall Quote Link to comment Share on other sites More sharing options...
cipx2 Posted September 23, 2007 Share Posted September 23, 2007 Check pin 9 from connector C0793 on AC ECU which is "Cooling fan request" to ECM. That way you will know which one issues the command for the fan to come on, AC ecu or ECM ecu. Quote Link to comment Share on other sites More sharing options...
lynall Posted October 8, 2007 Author Share Posted October 8, 2007 Right done some more testing with trusty multimeter and have found the following:- the ac ecu is switching as its meant to for the cooling fan control pin 9, the engine ecu is supplying an earth path to the fan relay as soon as engine is started black plug pin 4. Not sure if its faulty ecu or the ecu is getting a signal from a duff sensor thats saying its hot run that bloody fan! Any ideas? cipx2 thanks for the pin info on the ac ecu. Bogmonster thats a pretty extensive description! have checked all wires can see no damage, everything switchs as it should. I have even put std chip back in ecu on the off chance but no difference. I just know its something stupid (prob me) but am not sure what. Only thing i have changed recently is the fuel pressure regulator which came with a new sensor this also checks out with multimeter according to Rave. Thanks for the replies and info much appreciated Lynall Quote Link to comment Share on other sites More sharing options...
lynall Posted October 8, 2007 Author Share Posted October 8, 2007 Have also stuck in a new temp sensor again no difference reads same as old one. Lynall Quote Link to comment Share on other sites More sharing options...
JimAttrill Posted October 8, 2007 Share Posted October 8, 2007 The answer is simple, folks. Your ECU has sensed that at some time your engine was overheating. It then switches the aircon fan on to help out. Unfortunately it will not switch it off again until the fault is cleared using a pooter. We do this all the time here, although maybe the ambient temps don't help. It is a not-really-helpful feature of the ECU. We clear the faults for free, but apparently LR stealers charge a lot just for doing this. Well, it helps pay for the tiled workshop floors and all the gear the mechanics wear. Quote Link to comment Share on other sites More sharing options...
cipx2 Posted October 8, 2007 Share Posted October 8, 2007 Yes, this could be the problem. There's a guy down under complaining about this: http://www.aulro.com/afvb/showthread.php?t=44449 Quote Link to comment Share on other sites More sharing options...
lynall Posted October 9, 2007 Author Share Posted October 9, 2007 Hey you two thanks for that, i would never have thought of that. Amazing and maybe a cheap fix? Lynall Quote Link to comment Share on other sites More sharing options...
BogMonster Posted October 9, 2007 Share Posted October 9, 2007 Interesting - never heard of that before but then overheating is not a big feature of our day here Quote Link to comment Share on other sites More sharing options...
JimAttrill Posted October 11, 2007 Share Posted October 11, 2007 Nor ours at the moment as it has been raining and cold (10c) for a few days now. We have 3 overheated TD5s in the workshop at the moment.... Luckily none of them seem to have a cracked head or block, so we can get away with the gasket, hopefully. TD5 cylinder heads are unfortunately only available from LR here, which makes them ridiculously expensive, often about as much as the vehicle is worth. The only thing to do in that case is to fit a second hand engine from a rolled vehicle. And there are a few of those around. Quote Link to comment Share on other sites More sharing options...
Ali Zafar Posted October 8, 2019 Share Posted October 8, 2019 On 10/8/2007 at 5:27 PM, JimAttrill said: The answer is simple, folks. Your ECU has sensed that at some time your engine was overheating. It then switches the aircon fan on to help out. Unfortunately it will not switch it off again until the fault is cleared using a pooter. We do this all the time here, although maybe the ambient temps don't help. It is a not-really-helpful feature of the ECU. We clear the faults for free, but apparently LR stealers charge a lot just for doing this. Well, it helps pay for the tiled workshop floors and all the gear the mechanics wear. Hi,I have the same issue and I have taken my car to the dealership twice and they had no idea about this issue. I got them to hook it up to the system called T4 which apparently is LRs genuine diagnostic system for the TD5. However, I tried going through the menus but couldn't find any option to turn the fans off.If anyone here is familiar with this system, can you please guide me going through what menus will lead me to an option to turn this forced assist off.You help is much needed and would be really appreciated!!I am from Pakistan and the TD5 Defender was never launched here but the dealer has some experience with TD5 Discos. Quote Link to comment Share on other sites More sharing options...
JohnnoK Posted October 9, 2019 Share Posted October 9, 2019 The Nanocom diagnostic box can do it, but it wouldn't surprise me if the OEM one couldn't. Maybe consider buying a Nanocom, if you intend keeping the Landy, better, too, if you have mates who have vehicles with OBD-II connectors, because all you will need then is to buy the software and the appropriate cable for the various models, and you can start making some side money doing diagnostics. Quote Link to comment Share on other sites More sharing options...
JimAttrill Posted January 4, 2020 Share Posted January 4, 2020 I have a Nanocom that I don't use as my engine is a 300tdi and I don't work on Landys any more. Quote Link to comment Share on other sites More sharing options...
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