andytmc
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| posted on 7/8/05 at 07:08 PM |
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Zetec ECU reluctant to start radiator fan...
Hi
I'm using the standard Ford ECU to run my Zetec 1.8. The engine runs a treat but the radiator fan doesn't seem to want to play.
Looking in the Haynes manual, its a bit complicated as some variants support 2 fans. I identified the control wire for fan 1 from the ECU , and wired
this into a proper Mondeo relay. This relay is a 5 pin item that I think has some sort of voltage regulator in it ??
Heres what happens. When the engine is started (hot or cold), the fan runs for approx 1 min then stops. The Haynes manual says the fan should kick in
at 100C but the temp gauge reads 110 and no fan.
I'd be very grateful for any advice on this as its driving me up the wall!
Many thanks
Andy
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JoelP
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| posted on 7/8/05 at 07:19 PM |
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hi mate.
on my car (1600 crossflow engine) the fan is wired up to be constantly on. It still runs on the hot side  So it might be easier just to give it a
perminant feed, maybe off the auxilliary ignition position so you can kill the engine but leave the fan on in a queue
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Danozeman
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| posted on 7/8/05 at 07:32 PM |
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What fan switch are u using mate? The standard one in the thermo housing?
Dan
Built the purple peril!! Let the modifications begin!!
http://www.eastangliankitcars.co.uk
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davidwag
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| posted on 7/8/05 at 09:29 PM |
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hi,
The cooling fan on a mondeo is controlled by the ECU.
Temperature reference is from the coolant temp sensor on the top of the thermostat housing. There is not a separate fan switch.
What year and model is it from?
Was it from a car with air con?
Are you using the original engine wiring loom?
David
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andytmc
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| posted on 8/8/05 at 08:49 AM |
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Thanks for the replies.
The engine is a 1996 vintage. I didn't remove the engine from the donor but when it arrived there wasn't any sign of air con.
The standard engine loom is being used prettry much as standard with some changes to reflect the fact that the Mondeo relay box isn't being
used.
last night I noticed in the Haynes manual they list some resistance at given temperature values for the coolant temp sensor. I'll check this and
see if its in spec.
Many thanks
Andy
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andytmc
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| posted on 9/8/05 at 08:41 PM |
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Coolant sensor checks out OK, so back to head scratching!
Looks like I may be heading the external thermostat route....
Andy
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davidwag
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| posted on 10/8/05 at 08:10 AM |
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hi,
The mondeo cooling fan relay should be connected as follows.
Pin1 Ignition live (normally from relay in aux fuse box)
Pin2
Pin3 Constant live supply from battery through 60 amp fuse
Pin4
Pin5 Supply to cooling fan
Pin6 Control wire from ECU
Pin7 Ground
If you dis-connect the ecu then switch ignition on then short pin 6 to ground cooling fan should run. This will tell you if is a fan or ecu fault.
David
[Edited on 10/8/05 by davidwag]
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andytmc
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| posted on 10/8/05 at 10:30 AM |
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Hi David
I'll double check the connections and let you know how it checks out.
Many thanks
Andy
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andytmc
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| posted on 10/8/05 at 07:23 PM |
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I checked the wiring again as per Davids advice, and spotted the slight error that the signal wire from the ECU was the wrong one. Well at least it
was the right colour!
Anyway I swapped for the correct wire and earthed the connection - the fan started. Much encouraged I started the engine. The fan started straight
away which wasn't what I was hoping for...
After further testing, it seems that the ECU signal is earth while the engine is cold, and then switches to open circuit when the temp reached
100C.
So I think if I use a normally closed relay instead of a normally open one it should sort it.
Andy
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davidwag
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| posted on 10/8/05 at 08:28 PM |
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Hi Andy,
Have rechecked wiring diagrams and the above connections should be right.
The diagrams show a normally open relay. So the ECU should have to earth the Black/blue wire (from ECU pin 13 to relay pin 6) on order for the relay
to work.
David
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andytmc
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 posted on 13/8/05 at 07:05 PM |
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Solution
I junked the Momdeo relay and put in a normal 5 pin relay instead.
These relays make 2 circuits, one when the realy is acivated and one when it is not. As the ECU is sending earth when the engine is cold and then open
circuit when the fan should start, I connected the fan to the output that was made when the the ECU sends open circuit.
Fan now kicks in just before 100C and switches off below 90C.
Its a bit strange that the ECU works like this for the fan control, every other circuit switches to earth when something should happen.
Thanks to everyone that replied,
Andy
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