99 Disco 1 electric cooling fans
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3rd Gear
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99 Disco 1 electric cooling fans
My electric fans only run when the a/c is on. One fan runs briefly at start up and then stops. Arent they supposed to come on if the temp gets above 212 when the a/c is off? What controls the non a/c switching of the fans?
Thanks
Thanks
Super Moderator
Joined: Jan 2011
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From: Savannah Georgia
That is stated for the D1 with MFI injection, but for SFI (NAS) the following text appears in the RAVE, which basically says the ECU will turn on the fan relay when it wants to. It does not say 100C like the other injection systems. May be a typo.
that Condenser Fan Motor operation is required.
M121).
So IMHO, if the ECU is given bad info, like a low reading coolant temp sensor, it may not switch on. Note fom the drawing that a single relay controls both fans, you should not have just one fan switch on ever. My electric fans spin for a short time at cold start because of the air flow from my main rad fan, but they are not powered up.
Condenser Fan Operation (NAS) (SFI–V8)
The Condenser Fan Motors (M113, M121) on
vehicles equipped with SFI–V8 engines operate
when any of the following conditions occur:
1. The A/C system is operating.
2. The Engine Control Module (ECM) determines
The Condenser Fan Motors (M113, M121) on
vehicles equipped with SFI–V8 engines operate
when any of the following conditions occur:
1. The A/C system is operating.
2. The Engine Control Module (ECM) determines
that Condenser Fan Motor operation is required.
With the Ignition Switch (X134) 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). When Condenser
Fan operation is required, the Engine Control Module
(ECM) (Z132) grounds terminal 85 of the Condenser
Fan Relay (K109). The relay energises, applying
battery voltage from fuse F3 of the Engine
Compartment Fuse Box (P125) to the Condenser
Fan Motors (M113, M121). When Condenser Fan
operation is no longer required, the ECM removes
the ground supply to the Condenser Fan Relay
(K109). The relay de–energises, removing the
voltage supply to the Condenser Fan Motors (M113,
voltage is applied to the Ignition Load Relay (K127).
The relay is energised, applying battery voltage to
the Condenser Fan Relay (K109). When Condenser
Fan operation is required, the Engine Control Module
(ECM) (Z132) grounds terminal 85 of the Condenser
Fan Relay (K109). The relay energises, applying
battery voltage from fuse F3 of the Engine
Compartment Fuse Box (P125) to the Condenser
Fan Motors (M113, M121). When Condenser Fan
operation is no longer required, the ECM removes
the ground supply to the Condenser Fan Relay
(K109). The relay de–energises, removing the
voltage supply to the Condenser Fan Motors (M113,
M121).
So IMHO, if the ECU is given bad info, like a low reading coolant temp sensor, it may not switch on. Note fom the drawing that a single relay controls both fans, you should not have just one fan switch on ever. My electric fans spin for a short time at cold start because of the air flow from my main rad fan, but they are not powered up.
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3rd Gear
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I do not have any voltage at either wire that connects to the coolant temp switch. The cooling fans never come on no matter how hot the engine gets. Can the relay be bad but stilll run the fans when the a/c is on? Is the there a fuse that controls voltage to the coolant temp sensor?
Thanks
Thanks
Super Moderator
Joined: Jan 2011
Posts: 16,322
Likes: 88
From: Savannah Georgia
It is a sensor (not an on/off switch) , varies in resistance. Both sides go to the ECU, so any voltage will be very low. Spec is
• Output = Approx. 4.7v at -30°C (-22°F) to 0.25v at 130°C (302°F). Approx. 0.7v at 85°C (185°F)
You can also see what temp the ECU thinks it is sending with a scanner or ultra gauge.
Pix of coolant sensor, it is one on the right with two wires, square top. Left one is one-wire gauge sensor.
Last edited by Savannah Buzz; Nov 12, 2012 at 09:34 AM.
You can also see what temp the ECU thinks it is sending with a scanner or ultra gauge.
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