ducato cooling fan constantly on

[gwgw]

Hi everyone, i hope you can help:
One cooling fan is constantly on as soon as the ignition key it turned, the other is off.
So far I have replaced the radiator temp.,sensor blue in colour. Also the air temperature sensor in the radiator cowling, black with green coil. I have also replaced the two relay units. which has not rectified the fault... if anyone has the wiring diagram it would be most welcome. I can only assume that there is a cable broken, and there is some kind of failsafe system activated.
Its a fiat ducatto based motorhome 1999 2.8 turbo diesel... Any advise would be gratefully received. I notice another post had a similar problem but no update was posted on how it was rectified. Many thanks a frustrated fiat ducatto owner.

 

[varesecrazy]

Hi everyone, i hope you can help:
One cooling fan is constantly on as soon as the ignition key it turned, the other is off.
So far I have replaced the radiator temp.,sensor blue in colour. Also the air temperature sensor in the radiator cowling, black with green coil. I have also replaced the two relay units. which has not rectified the fault... if anyone has the wiring diagram it would be most welcome. I can only assume that there is a cable broken, and there is some kind of failsafe system activated.
Its a fiat ducatto based motorhome 1999 2.8 turbo diesel... Any advise would be gratefully received. I notice another post had a similar problem but no update was posted on how it was rectified. Many thanks a frustrated fiat ducatto owner.

Shame its too early for plugin diagnostics

Does it have two fans / feeds..??

Is aircon mounted near it..??

Charlie

 

[gwgw]

Shame its too early for plugin diagnostics

Does it have two fans / feeds..??

Is aircon mounted near it..??

Charlie

Hi Charlie, it does have two fans which are both fed from the same fuse [30A located by engine battery]. It also has aircon but this is no longer in use and has been disconnected by the previous owner.

Cheers geoff

 

[varesecrazy]

Hi Charlie, it does have two fans which are both fed from the same fuse [30A located by engine battery]. It also has aircon but this is no longer in use and has been disconnected by the previous owner.

Cheers geoff

Hi Geoff,
the reason I ask is - on the little cars the single fan runs at 2 speeds

so it could've been a diagnostic aid,

as you've essentially covered all the obvious..barring a lost earth - and it running constantly as a by-product..,
I'd be tempted to disable it, and run a new switched supply to the fan.

:idea:have you tried pulling fuses to see if it's being oddly powered by another circuit.

(there is a common issue on old punto's - where the sidelights appear to come on randomly.. it's actually a cabin fan wiring fault..)

Charlie

 

[gwgw]

Thanks for your input, i shall investigate further over the weekend.
I have already fitted a manual switch that i use when the gauge rises too much but i was hoping to revert back to normal, just so i don't have to keep staring at the temp gauge.

Hopefully i will have something to report after the weekend.

Thanks again
geoff

 

[gwgw]

Couldn't resist checking out what you said about an extra feed, yes you were right.
There are two fuses killing the same feed, a 30A by the engine battery and a 30A inside the glovebox fuseboard.
Now i'm even more confused
I've looked under the passenger dash as below the glovebox are lots of relays, there are two missing [blue and brown] which i assume were for the AC ?
I also checked the heater blower resistor which is fine.
The plot thickens:bang:

 

[gwgw]

Hi again, i removed the radiator blue sensor switch. I then shorted out two of the three wires, this kicked in the nearside fan. The strange thing is this happened whilst all three relays were removed from the rad cowling.
Surely the sensor switch operates the relay as the wires are small in size.
I checked voltage at the sensor and the one of the three wires is live as soon as the ignition is switched on.

Any suggestions are most welcome

Thanks

 

[varesecrazy]

Hi again, i removed the radiator blue sensor switch. I then shorted out two of the three wires, this kicked in the nearside fan. The strange thing is this happened whilst all three relays were removed from the rad cowling.
Surely the sensor switch operates the relay as the wires are small in size.
I checked voltage at the sensor and the one of the three wires is live as soon as the ignition is switched on.

Any suggestions are most welcome

Thanks

Hi again.

Maybe post an update in the DUCATO SECTION

Not sure people are seeing this.
Charlie

 

[varesecrazy]

Hi again, i removed the radiator blue sensor switch. I then shorted out two of the three wires, this kicked in the nearside fan. The strange thing is this happened whilst all three relays were removed from the rad cowling.
Surely the sensor switch operates the relay as the wires are small in size.
I checked voltage at the sensor and the one of the three wires is live as soon as the ignition is switched on.

Any suggestions are most welcome

Thanks

turns out there was a broken wire near RHS Headlight - mentioned in the other thread.

"Finally sorted it. I basically followed the wires from the switching side of the fan relay, these went down towards the floor then across by the starter motor and then up towards the battery.
From there they headed toward the rhs headlight, it was here i found the cable [very small in diameter] had broken.
Soldered it up and all works perfect."