electric fan
Super Moderator
Joined: Jan 2011
Posts: 16,322
Likes: 88
From: Savannah Georgia
The fan has a mind of its own - well, the ECM does the thinking. Should be able to add a switch to supply the ground point as a manual over ride. Important point when working on electric condenser fans - don't reverse polarity or mount blades bacjkwards. Air will blow out the grille of the truck. At low speeds and idle, that air is being "subtracted" from the reguular air flow of the main radiator fan, and overheating happens.
BTW - if your temp gauge is nudging up, you have more serious issues - check with data reading scanner to confirm the real temp inside the engine. What looks like "normal" is certainly not when above 9:00 position on the idiot light with a pointer (temp gauge).
See RAVE:
[On a D1 things are different, fan is on whenever AC is engaged, or when coolant temp over 212F, or after engine off if coolant temp and fuel temp are above certain level, then it will run 10 minutes)
BTW - if your temp gauge is nudging up, you have more serious issues - check with data reading scanner to confirm the real temp inside the engine. What looks like "normal" is certainly not when above 9:00 position on the idiot light with a pointer (temp gauge).
See RAVE:
General
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 degrees C (212 degrees F) V8, 110
degrees C (230 degrees 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 degrees
C (140 degrees 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 below 12va 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 degrees C (212 degrees F) V8, 110
degrees C (230 degrees 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 degrees
C (140 degrees 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
OPERATION
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.
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.
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 fan motor..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
[On a D1 things are different, fan is on whenever AC is engaged, or when coolant temp over 212F, or after engine off if coolant temp and fuel temp are above certain level, then it will run 10 minutes)
Thread Starter
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Three Wheeling
Joined: Sep 2011
Posts: 68
Likes: 0
From: Keedysville, Maryland
will the electric fan only work when the key is on? i think have heard my car fan running even after i have got out of the car and turned it off.
i'm going to add a manual switch either way just for wheeling. And i'm going to get either ultra gauge or scan guage soon too.
thanks
Super Moderator
Joined: Jan 2011
Posts: 16,322
Likes: 88
From: Savannah Georgia
It would work with the key off, only if engine was too warm when switched off. Good idea on the manual switch for wheeling, long hills with a trailer, etc. In theory it knows when to turn on, but it can't anticipate that you just turned off the pavement into the relax and rewind zone.
Administrator
Joined: Apr 2006
Posts: 25,707
Likes: 107
From: Denver, Colorado
Go start and let your engine idle out on the drive way with the a/c on. Within a couple of minutes, with the engine at normal operating temp. you should be able to stand in front of the truck and hear the fan working. Check it and get back to us.
Super Moderator
Joined: Jan 2011
Posts: 16,322
Likes: 88
From: Savannah Georgia
I forgot to mention that the fan is controlled by fuse 5 in the underhood fuse box, and fan relay # R 117, like Mike says, it should cycle from time to time with AC on. If it was not working, you could be having poor AC operation in traffic and while stopped.
3rd Gear
Joined: May 2013
Posts: 3
Likes: 0
I got a 99 Disco II about a month ago, and I noticed I never heard the electric fan kick on. It even blew a hose off and got hot one day and the fan never ran. I have noticed the fan kick on at seemingly random intervals, especially when I first start it up some mornings. After reading this, I'm wondering if the aftermarket intake is having an effect on the air inlet sensor reading (says the fan will only come on if the air temp is above 60 degrees)
Baja
Joined: Feb 2011
Posts: 9,298
Likes: 318
From: Boston Strong
the random intervals should be when your truck reaches 212 degrees, the fan you hear in the morning at startup is the clutch fan, total different fan. What kind of aftermarket intake manifold could you be running on a DII?
Super Moderator
Joined: Jan 2011
Posts: 16,322
Likes: 88
From: Savannah Georgia
You'll be wanting to look at a scanner or Ultra Gauge so you can see those coolant temps, factory gauge points at 50% from 130-240F. Many owners find electric fan won't spin freely, the drag on the blades from siezing up makes the DC motor reach what is called "locked rotor amps" and the fuse blows and or relay fries. A blown fuse on a radiator fan is a sign of lock up. The extra heat load not being handled by the cooling system does not go un-noticed for long by the head gasket.
3rd Gear
Joined: May 2013
Posts: 3
Likes: 0
The electric fan does not kick on when its above 212, if so it would have been running when the hose blew off. When I said the electric fan would run sometimes when I first start it up, that's exactly what I meant, not the clutch fan, I can see the electric fan spinning. Fuse and relays all checked out.