AC fan running on

1998 D1, the air con fan runs constantly while the ignition is on and for 10minutes after being switched, I've read this is because its got hot and it's trying to cool itself down, the temp is normal and it's done this since I got the disco, how can I get the fan to work as normal?
I cant find a wiring diagram for the timer relay either.

Jackstar said:

1998 D1, the air con fan runs constantly while the ignition is on and for 10minutes after being switched, I've read this is because its got hot and it's trying to cool itself down, the temp is normal and it's done this since I got the disco, how can I get the fan to work as normal?
I cant find a wiring diagram for the timer relay either.

Click to expand...

Ok the AC fans, u have two so both will run when the AC system is in use.

Your correct the fans will continue to run after the engine is switched off or or a few minutes later as heat builds up in the engine bay, the reason is that the engine bay temperature is NOT normal it’s higher than normal therefore the thermo switch operates, it should only happen when the ambient temperature is high, if it happens when ambient temps are not high then theres a possibility the viscose coupling isn’t function as it should.

When the ambient temp is high as recently my disco AC fans have been known to continue to run, the engine bay is like an oven even with the viscous coupling fully locked…. Well it has two exhaust manifolds so understandable.

You'll have to use a diagnostic tool to check the live temperature inputs to make sure that the conditions are not met for the fan to run that way cos it can be a faulty temp sensor also it's possible to have an overheating fault code logged then you'll have to clear the code to stop the fan, click on cooling fans to see the operation mode here https://cardiagn.com/1997-1999-land-rover-discovery-1-electrical-troubleshooting-manual/

Iirc d1 a/c switch is in top of stat housing?

Could be the switch has failed to 'always on'?

sierrafery said:

You'll have to use a diagnostic tool to check the live temperature inputs to make sure that the conditions are not met for the fan to run that way cos it can be a faulty temp sensor also it's possible to have an overheating fault code logged then you'll have to clear the code to stop the fan, click on cooling fans to see the operation mode here https://cardiagn.com/1997-1999-land-rover-discovery-1-electrical-troubleshooting-manual/

Click to expand...

Interesting, so where would the diagnostic tool be plug in and were would the AC fault codes be logged.??

It's not about AC fault here, the fault code and fan's controll is managed by the ECM too as the fan(s) are used for both aircon and additional engine cooling too in case of too hight engine temperatures. As the OP didnt say what engine but he said that it stays on 10 minutes after the ignition was off i presumed it's a V8 cos it's the only one with that 10 min operation, maybe the 300tdis with ECM too? (it behaves quite the same like the D2):
Condenser Fan Operation (MFI–V8)
The Condenser Fans Motors (M113, M121) on
vehicles equipped with MFI–V8 engines operate
when any of the following conditions occur:
1. Coolant temperature exceeds 100 C (212 F).
2. The air conditioning system is operating.
3. The Engine Control Module (ECM) (Z132)
determines that fuel temperature exceeds
70 C and coolant temperature exceeds 110 C
after engine shutdown. When this occurs, the
fans are on for approximately 10 minutes
after the engine is shut off.

sierrafery said:

It's not about AC fault here, the fault code and fan's controll is managed by the ECM too as the fan(s) are used for both aircon and additional engine cooling too in case of too hight engine temperatures. As the OP didnt say what engine but he said that it stays on 10 minutes after the ignition was off i presumed it's a V8 cos it's the only one with that 10 min operation, maybe the 300tdis with ECM too? (it behaves quite the same like the D2):
Condenser Fan Operation (MFI–V8)
The Condenser Fans Motors (M113, M121) on
vehicles equipped with MFI–V8 engines operate
when any of the following conditions occur:
1. Coolant temperature exceeds 100 C (212 F).
2. The air conditioning system is operating.
3. The Engine Control Module (ECM) (Z132)
determines that fuel temperature exceeds
70 C and coolant temperature exceeds 110 C
after engine shutdown. When this occurs, the
fans are on for approximately 10 minutes
after the engine is shut off.

Click to expand...

Well what your quoting is not for the UK spec for the D1 V8 with the Lucas - Bosch engine, or a 300Tdi without or without electronic diesel control.
The condenser fans on these models are operated via a thermo-switch… as already stated in posts above.

A copy from the UK addition of RAVE, and not a D1 fitted with a GEMS engine.
Fan timer unit
The thermostatically controlled timer will continue to operate the cooling fans after the air conditioning or ignition is switched off. When the system temperature is excessive, the fans will operate for 10 minutes to reduce condenser and under bonnet temperature.

I've ordered a new temperature sensor/switch, hope I got the right one.
There's a sensor in the thermostat housing and two in the inlet manifold.

Sorry should have said in the 1st post, it's a 3.9 v8

Jackstar said:

I've ordered a new temperature sensor/switch, hope I got the right one.
There's a sensor in the thermostat housing and two in the inlet manifold.

Click to expand...

The two are EFI ECU engine temp thats by the dizzy and the other is fuel temp.
The item that controls the over run is on the face of the stat housing.
As u have ordered, I wont need to go and find the part number

Jackstar said:

Sorry should have said in the 1st post, it's a 3.9 v8

Click to expand...

Big Blue ?

discool said:

Well what your quoting is not for the UK spec for the D1 V8 with the Lucas - Bosch engine, or a 300Tdi without or without electronic diesel control.

Click to expand...

I dont want to contradict you nor to argue just to solve this problem eventually. I was quoting from the Electrical troubleshooting manual linked in my first post which i think is general for all types, open that doc and see Cooling fans. Your quote is about the fan timer unit which has two operation modes,

1. With engine running when it's controlled by that temp switch from 100*C
Operation with High Coolant Temperature(MFI–V8)
When the Ignition Switch (X134) is in position II,battery voltage is applied to the Ignition Load Relay(K127). The relay is energised, applying battery voltage to the Condenser Fan Relay (K109) and theFan Control Module (Z118). If the coolant temperature exceeds 100C (212F), the Condenser Fan Coolant Temperature Switch (X113) closes and energises the Condenser Fan Relay (K109) by applying ground to the relay’s coil. ...

2. With engine off when the timer unit is triggered by the ECM cos it's the only one which can determine that the ECT exceeded 110*C or FT 70*C, the switch cant do that as it closes at 100 then if the ECT doesnt reach 110*C the fan will not run with engine off.
Operation with the Engine Off (MFI–V8)
The Engine Control Module (Z132) monitors fuel temperature and coolant temperature through sensors. When the ECM determines that fuel temperature is above 70C and coolant temperature exceeds 110C after engine shutdown, the ECM will command fan operation for approximately 10 minutes. The ECM turns on the fans by momentarily grounding the Fan Control Module (Z118) throughthe BG wire. When the timer unit is grounded, it starts a solid state timer and begins to apply groundfrom its terminal 9 to the Condenser Fan Relay(K109) through the BP wire.

So IMO as long as the fan runs with engine off for 10 minutes the fan timer unit which you described can be triggered to do that only by the ECM not by the temp switch as the 14 CUX ECM has output for the fan control module on pin 36, see this https://blackbox-solutions.com/help/SM006.html... i doubt that changing the temp switch would solve this problem, eventually the engine coolant temp sensor... though if i'm wrong then my apologies.

I've not changed anything yet but I had the disco idling while I was in the garage and the fan turned off, I clicked the AC on and it came back on as it should, Turned the ignition off and one again but the fan came straight on again with no AC on.
Nearly fixed itself lol
@sierrafery do you think that if I pull the wire from pin 36 that will stop the fan from working as a engine cooling fan as the relay won't be getting the signal to start.
I won't need the ac fan to work as an engine cooling fan as I've got a twin electric setup coming for the radiator.
I would however like it to work with the AC as it should.

Jackstar said:

... do you think that if I pull the wire from pin 36 that will stop the fan from working as a engine cooling fan as the relay won't be getting the signal to start.

Click to expand...

Probably but you should investigate why it happens cos it's possible that the ECT or FT sensor to be faulty then it is bad for te engine management too also if there is an overheat fault code stored in the ECU memory it should be erased

I've tried my code scanner but guessing that it's too old for scanners.
I tried the new ect sensor on today but made no difference.
I've just removed the timer relay for now, it works fine as an AC fan and doesn't run all the time like before, I do see what you mean about a faulty sensor that could be making the engine less efficient.