Hi Everyone,I hope someone can help me with info. I've had my 1.9TD Fiat motorhome laid up over winter- had all the batteries disconnected. I've just charged up the main battery and when I put it in, the cooling fan started up and it will not stop unless I disconnect it at the fan end. I thought the fan was supposed to kick in when the engine warmed up and then go off. I have never had this problem before and it sounds like an electrical problem to me but how do I solve it. Its a 1998 FD.Autoroller.

Hi Kamperman

I'm no expert but normally there's a heat sensitive switch screwed in at some point towards the top of the radiator, with two wires coming from it, which under correct working conditions will "kick in" when the radiator temperature becomes overheated.

The fact that yours is on all the time would tend to indicate this switch has failed or is short circuiting. Hope this may help. Cheers

Thanks for that info. Shingy. I also think its a short somewhere. Now to find those wires you mentioned. If I can't sort it myself I'm sure my mechanic will be able to fix it.

I've just joined because I had almost the same problem today, and was looking for an answer!

I was out in my 1999 1.9TD motorhome today, and parked to have lunch and go for a walk. The fan was still running after about 45 minutes, draining the battery, and there wasn't enough left to start the engine. I was obviously stuck, so called my breakdown recovery or the first time in the 7 years I've had it. After an hour I found a plug that I could pull out to disconnect it, then plugged it in again and it didn't start running. After the breakdown man jump started it (and assured me there would be enough in the battery to be able to restart it!) I went shopping and stopped and restarted the engine twice, but each time had to disconnect the fan to stop it running. When I got home, I unplugged the fan, but for the next half hour or so it started running when I reconnected it, then it was OK. Is this most likely to be the sensor, which is on the left hand bottom of the radiator?

Yes, got to be the sensor screwed into the radiaor at fault, same as Kamperman I reckon. You could check the two wires going to it for corrosion, but I expect you've already done that. Should be a not very expensive DIY job. Good luck.

Hi there JohnandBeauty. Shingy was right about my cooling fan problem. I checked the wiring at both ends and it seemed alright. The sensor at the bottom of the radiator was the problem. It was somewhat corroded.My garage managed to get hold of one and put it in.Working fine now. Cost £60 including having radiator drained and new coolant put in.

Just joined FF with same problem on my 1996 Fiat based motorhome. Last year had to manually disconnect wait for a while then reconnected. Had garage look at it when they did MOT and told me unable to find anything wrong. Now when connected runs all the time. Off to have a look at sensors etc. Seems likely that after 24 years will be some corrosion especially as low millage. Need to get this sorted before lockdown ends

simple and cheap fix(temporary if you like) find the earth wire to the fan that's the problem,cut it and re wire through a switch in cab.If the fan stays on after a run switch it off.My kontiki has been like this for about 3 years even if you forget to turn it on it's not a problem since they have two fans,and the second only comes on as the overheat point nears.Saves finding a sensor draining the rad etc,and can be fitted in about ten minutes.

kennatt said:

simple and cheap fix(temporary if you like) find the earth wire to the fan that's the problem,cut it and re wire through a switch in cab.If the fan stays on after a run switch it off.My kontiki has been like this for about 3 years even if you forget to turn it on it's not a problem since they have two fans,and the second only comes on as the overheat point nears.Saves finding a sensor draining the rad etc,and can be fitted in about ten minutes.

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The radiator fans are perhaps the most power hungry accessories and on my vehicle are fused at 40A each. It follows that any additional wiring should be capable of carrying this current. Otherwise there may be a fire risk.

indeed hence the advice to switch the EARTH

kennatt said:

indeed hence the advice to switch the EARTH

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I would remind readers that the same fan current will flow in both positive and negative wires.

With non common rail engined vehicles as Roger B's vehicle will be, it should be possible to locate the thermostat, and intercept the controlling negative wire to the appropriate fan relay. This would result in the need to switch a very much smaller current.

Switching via the fan relay is not practicable with comon rail engines, as fan control is by sensor and the ECU.

I think that the effort taken in running wires and installing a switch would be better spent in replacing the faulty thermostat. I accept that this requires partial draining of the cooling system. This is the approach that I understood Roger B was taking.

Many years ago I had a similar problem with a Talbot Express. In that incident the fan thermostat was operating momentarily well below normal fan cut in temperature. I only noticed it by the dip in engine revs as it took up the fan load. It took some investigating to find the cause.