I

ItalianLandy96

New Member
Hello gents,
I have a 1996 Defender 90 2.0 mpi, I have done a bit of troubleshooting and am looking for some insight. My radiator fan does not kick on and I noticed I was overheating in traffic this weekend. I have only had the old girl for 6 months so I can't even remember the fan coming on since I've owned it. I have checked the obvious things (upper and lower radiator hoses are warm), all sensors are plugged in tight, I did measure the voltage going into the fan and noticed it was 0.3 VDC. Is there a sensor that sends power to the fan? Any help would be appreciated.
 
ItalianLandy96 said:
Hello gents,
I have a 1996 Defender 90 2.0 mpi, I have done a bit of troubleshooting and am looking for some insight. My radiator fan does not kick on and I noticed I was overheating in traffic this weekend. I have only had the old girl for 6 months so I can't even remember the fan coming on since I've owned it. I have checked the obvious things (upper and lower radiator hoses are warm), all sensors are plugged in tight, I did measure the voltage going into the fan and noticed it was 0.3 VDC. Is there a sensor that sends power to the fan? Any help would be appreciated.
Click to expand...

It will almost certainly be relay switched and the relay possibly switched by the engine ecu reading the coolant temp sensor/s.
Some motors have two coolant sensors 1 for the dash gauge and 2nd for the ecu to read.
I should imagine that engine is pretty rare even over there and in the UK almost non existant.

I would try a rover forum to see if there is a classic rover facebook page
 
Sounds good, I am on an Italian FB group just for 2.0 Mpi Defenders, but no responses yet. I suspected it may be a signal from the ECU and it does look like there are 2 temp sensors, but without many electrical diagrams out there for this model it is difficult to try and troubleshoot. These engine Defenders are a dime a dozen here as most are retired and sold at auction now.
 
I would guess it is the same setup as the Discovery 2.0 Mpi which was sold in the UK. So might give you something extra to Google for.
 
I managed to get a disco elec manual that covered the MPI, hoping that the basics are the same (less frills) off the net. Have a search for discovery electrical troubleshooting manual.
From what I can see it has 2 senders (they have different numbers in the drawings) 1 is used for the gauge and the other is for the fan. it runs through the ecu too a relay, to switch fan

what it’s like in practice I can’t say as not had to get in amongst ours. Might get a look if I get the chance over next couple of days.

J
 
ItalianLandy96 said:
Brilliant! Thank you for the info, what is the name of the book if you don't mind me asking? I may have to pick up a copy!
Click to expand...

free :) try this link http://rave.stringsandints.com/Disco_elec_manual_LJBEMENR95.pdf

But it won’t cover the whole of the defender only the MPI engine areas and ECU input/output for most things I believe, but as I said I haven’t yet had to break it out in anger so not 100% it’s accurate.
best to be on the hunt for a defender one for the rest of it.

hope it helps.

J
 
Mate you may have saved the day! Thank you for the assistance. I will print this beauty off tomorrow...now to follow the wiring and see what isn't working. The suspect would be X126 since X114 is what is sending the temperature to the gauge.
upload_2019-12-22_22-41-3.png
 
marjon said:
Glad to help:)

please let us know how you get on..

J
Click to expand...
Well it was finally warm enough to test if the replaced switch was the original problem....no it wasn't....luckily you can unplug the switch and the radiator fan comes on, but I don't want that to be the solution.
 
Are you sure it got warm enough?
Mine will sit for 15mins at idle and not come on at the moment. When you disconnect the plug does the idle speed up a little?
Mine acts exactly like you are describing plus a slight raise in idle when the plug is removed, maybe mine not working either :eek:
funny enough somebody has already changed mine as the old 1 is still in the car.

J
 
I was driving into work, luckily there was enough traffic to jump out and pull the plug so it would turn on. I could see the temp rising past center on the dial.
 
ItalianLandy96 said:
I was driving into work, luckily there was enough traffic to jump out and pull the plug so it would turn on. I could see the temp rising past center on the dial.
Click to expand...

Ok but is that actually hot enough?
I don’t see mine above center.

You really need to start checking with a meter to check values of the sensor when cold and hot.
The MPI rad is plenty big enough to cool at standstill. Although if you have been giving it some work and then come to a stop it may need the assistance.
Are you sure your water pump is ok and you have no air locks in the system?
How’s the heater?
I assume you have the right sensor?

J
 
marjon said:
Ok but is that actually hot enough?
I don’t see mine above center.

You really need to start checking with a meter to check values of the sensor when cold and hot.
The MPI rad is plenty big enough to cool at standstill. Although if you have been giving it some work and then come to a stop it may need the assistance.
Are you sure your water pump is ok and you have no air locks in the system?
How’s the heater?
I assume you have the right sensor?

J
Click to expand...
No air in the system, checked fluid level, heater works great, the fan just doesn't come on... changed the sensor and verified past numbers from the disco mpi 2.0 workshop manual.
 
I would go back to basics here.
Do you know what the real temp is? Do you have 1 of them laser thermometer things?
I have the old 1 in a bag with numbers on I could check.

have you a DVM to check resistance of the sensor old and new, and the new 1 when cold and hot.
I don’t know what they should be but could check against what I have if that’s any help.

you didn’t mention if idle raises or not.

All this depends on if mine actually works :eek: but I have never had any cooling issues.

J
 
Ciao guys
I've exactly the same issue in my 1994 discovery. I changed the two sensors but without results. For the moment I installed a switch to turn on the fans but I would like to repair everything. No ideas where to check now. Is there a way to read the engine ECU error to try to understand? Thanks in advance
 
DiscoMPI said:
Ciao guys
I've exactly the same issue in my 1994 discovery. I changed the two sensors but without results. For the moment I installed a switch to turn on the fans but I would like to repair everything. No ideas where to check now. Is there a way to read the engine ECU error to try to understand? Thanks in advance
Click to expand...

Have you got the manual that was linked to earlier?
If I remember there is a relay in the circuit have you checked that?
If you disconnect the sensor does the fan come on?

As for reading the ecu sorry I have no idea, if you look around on some rover forums and see if they have the ability to read their ecus in the range that had the same engine.

J
 
Yes I put the switch that disconnect the sensor because I read this post and it works. The two fans turn on immediately. I also have a doubt because when I changed the sensors these wasn't water there but in the tank was at the correct level...moreover the gauge is always in the middle of the range also when I was overheating. Too many troubles, so I would be sure that the ECU is ok. I will also check into the manual
 
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