Technical 2001 Ducato Radiator fan running constantly

[Nickkdx]

I’ve just had fun replacing my radiator ( after one damaged in delivery, another manufacture fault and and another damaged but salavaged by using old part) in a 2001 Fiat Ducato 2.8idtd based motorhome, but now the radiator fans run constantly when the radiator switch is connected.
Is there anyway of test the switch or is it a case of buy new.
Cheers

 

[Communicator]

I believe that your radiator fans will be controlled by a two stage thermostat, via relays behind the dash.
You are obviously familiar with the thermostat, which should have 3 connections, specifically earth, fan 1, and fan 2. With a cold engine there should be no connection between any of the three connections on the thermostat when disconnected. A simple continuity test with test lamp, buzzer, or multimeter should suffice. I suspect that access for testing may be a problem.

Here is a link to a possible replacement on Ebay.

 

[Nickkdx]

So there should be no reading between any contacts on the switch. The one you link to looks ok and at that price it would be worth a try if if I get a reading between connections

 

[Communicator]

So there should be no reading between any contacts on the switch. The one you link to looks ok and at that price it would be worth a try if if I get a reading between connections
View attachment 460176

Normal arrangement is two contacts with a common connection. The first contact closes at a lower temperature than the second, so if temperature continues to rise with one fan running, the second fan is switched on. With a cold or normal temperature engine, I would not expect either fan to be operating, so the contacts will have to be open.

 

[Nickkdx]

Normal arrangement is two contacts with a common connection. The first contact closes at a lower temperature than the second, so if temperature continues to rise with one fan running, the second fan is switched on. With a cold or normal temperature engine, I would not expect either fan to be operating, so the contacts will have to be open.

More testing today, on a cold radiator.
3 wires to the switch and if I put my multimeter on continuity, I get a reading on common and one wire but not when I test common to the other wire.
Put a jump wire from common and one wire both fans start, so it’s the switch I think, as you said
Thanks

 

[Communicator]

More testing today, on a cold radiator.
3 wires to the switch and if I put my multimeter on continuity, I get a reading on common and one wire but not when I test common to the other wire.
Put a jump wire from common and one wire both fans start, so it’s the switch I think, as you said
Thanks

Are you testing the switch with it disconnected?
As both contacts should be open, you first test does suggest that the switch is faulty.
However, I am struggling to understand as to why your second test operates both fans.
Was the ignition on, or off, when the short was applied?
I have a memory of some engines not requiring ignition on for fans to run. This allowed cooling of a hot engine, after switching off. This was discussed in a thread, a few years ago, where fans were running continuously, akin to your problem.

 

[Nickkdx]

Yes fans running without ignition on.
When I did jump test common to the other contact I can hear a clicking in the bow at the top of fan shroud but with jump on the problem contact both fans run.
Switch ordered so will report back.
Cheers

 

[Communicator]

Yes fans running without ignition on.
When I did jump test common to the other contact I can hear a clicking in the bow at the top of fan shroud but with jump on the problem contact both fans run.
Switch ordered so will report back.
Cheers

I am still not happy as to why both fans start at the same time. You mention a clicking noise from the fan shroud. Some installations have a fan control box in that area. A forum search reveals mention of a faulty relay in such a box, so perhaps worth checking it out?

 

[Communicator]

@Nickkdx , I think that you will be interested in the following extract from a post on the MH Fun forum, made in January 2024. (I had bookmarked the page and then almost forgotten about it, but I still think that there was a similar problem to yours aired on FF.

"3) The 3 wire lower right corner mounted radiator temperature sender is a twin thermoswitch which grounds the fan relays. It switches at two different temps:
a) on first switch closing it controls a relay to fan 1 taking the ballast resistor out of circuit, hence changing from slow speed to standard.
b) on second switch closing a second relay energises fan 2 at standard speed."

 

[tommin]

I am still not happy as to why both fans start at the same time. You mention a clicking noise from the fan shroud. Some installations have a fan control box in that area. A forum search reveals mention of a faulty relay in such a box, so perhaps worth checking it out?

I concur here, there is a relay box on the fan shroud and they are prone to having issues. I would start here.

 

[Nickkdx]

@Nickkdx , I think that you will be interested in the following extract from a post on the MH Fun forum, made in January 2024. (I had bookmarked the page and then almost forgotten about it, but I still think that there was a similar problem to yours aired on FF.

"3) The 3 wire lower right corner mounted radiator temperature sender is a twin thermoswitch which grounds the fan relays. It switches at two different temps:
a) on first switch closing it controls a relay to fan 1 taking the ballast resistor out of circuit, hence changing from slow speed to standard.
b) on second switch closing a second relay energises fan 2 at standard speed."

I must of missed that thread on Motorhomefun.
When the switch arrives I will try it and then I can leave the campsite I’m on.
Then investigate the control box at later date when I get home and find a small spanner to remove the control box cover, which I have got with me.
Thanks

 

[airwave]

I’ve just had fun replacing my radiator ( after one damaged in delivery, another manufacture fault and and another damaged but salavaged by using old part) in a 2001 Fiat Ducato 2.8idtd based motorhome, but now the radiator fans run constantly when the radiator switch is connected.
Is there anyway of test the switch or is it a case of buy new.
Cheers

Oh dear , you have been put through the ringer ent ya ? .

If it makes you feel any better , i've had exactly the same thing with my small Suzuki van . The replacement leaked , second was assembled upside down , third one actually worked . They were all recored , but the second was a killer . Couldn't understand why the dam thing wouldn't fit until i realised it had been made up upside down . Took me ages to figure it out too . The third was my original , that had been recored on the hoof . Fair play to the guy , he did his level best to sort it out , even took to delivering them himself .

You seem to have your initial problem covered , so i'll stay outta the way . I have exactly the same van , just a year older at 2000 , but my advice would be the same . Only thing i would add , is in the main for information to @Communicator . The fan relays are mounted inside the engine bay , on the right hand fan shroud . They are not mounted inside the cab . But as you already have them this is immaterial anyway .