Technical 1998 1.7 Diesel Overheating Radiator fan not working

[PowellyEG]

Hi guys,

Ive had my punto for a good 2/3 months and so far been a trouble free 2k miles in her. Tuesday evening had to drive myself to hospital in it on the way there the red overheating light came on (the dont have a temp gauge).

Ive been down to see my mechanic yesterday and we have taken the thermostat off and tested that, it opens and closes fine, the water pump is all good an working, so we have put everything back together and re filled with summer coolant, bled the system (no air locks) and left it running for a while.

Sadly the radiator fan just doesn't kick in so heres the problem.

We have taken this off and tested it on a battery, it spins fine but only when we unplug the fan loom and connect a positive/negative feed directly to the motor on the fan. now we have 2 plugs one connects to the engine loom (checked the fuse too thats fine) and the other plug connects to the radiator and what I would presume is the water temp sensor.

Now is it the Fan? water temp sensor? why would the fan not kick in?

Thanks in advance for any help. I have tried your search function but found generic overheating threads. so all help appreciated.

 

[PowellyEG]

Bump.

Fans still not kicking in, not sure if its the whole fan unit or water / rad temp sensor ?

We have tested the fan and it does work but no way of testing off the fan loom ( 2 plugs on the fan unit)

Any help anyone??

 

[fingers99]

The fan/rad switch is likely to switch on the earth side. Investigate. If you short out the pins on the switch and the fan works, switch is faulty. Otherwise, you have an earth fault. This will be on the end of the cable to the switch which does not connect to the fan motor.

Some circuits use a relay. If present, that's another possible problem area.

I'm guessing you have a Mk1?

 

[s and b]

if you have no power coming down the loom cable then it cant run the fan
as said the switch in the radiator normally works by once the wax gets hot closing the pins to let current flow it makes the circuit by going to ground
therefore
if you have the therm switch in the radiator
you have a working fan
you would only need to run a wire from battery positive to switch a wire to the fan and a wire from the fan to earth
it might not be ideal but would certainly stop your overheating

stick an inline blade fuse near the positive battery terminal too something like 15 amps should do it

 

[fingers99]

Dreadful bodge. Overheating vs. overcooling.

Test for:

12v on one side of the fan connector. (Supply present)
Short the fan switch on rad (if fan works, likely switch fault)
Test for earth on side of fan switch which does not go to fan motor.

In all this, be logical. The fan circuit is liley to be uber simple, something like:

 

[PowellyEG]

Yeah Mk1 guys - have searched and sooooo many generic overheating threads, is it me or Fiat puntos the worlds most unreliable cars (no offence).

Ok so read about bridging the Fan temp switch from the thermostat, unplug and bridge -if fan comes on its the switch sensor / fan no work further issues, right?

 

[PowellyEG]

Dreadful bodge. Overheating vs. overcooling.

Test for:

12v on one side of the fan connector. (Supply present)
Short the fan switch on rad (if fan works, likely switch fault)
Test for earth on side of fan switch which does not go to fan motor.

In all this, be logical. The fan circuit is liley to be uber simple, something like:

BTW we have used a volt meter on the loom from the fuse on the right side, both were fine.

 

[fingers99]

Yeah Mk1 guys - have searched and sooooo many generic overheating threads, is it me or Fiat puntos the worlds most unreliable cars (no offence).

Ok so read about bridging the Fan temp switch from the thermostat, unplug and bridge -if fan comes on its the switch sensor / fan no work further issues, right?

Most Puntos are owned by people who really don't know or care -- and Mk1s are getting on a bit.

But, yeah. If it's getting the + voltage and nowt happens if the fan switch is bridged, the fault must be on the -ive side. Generally you can get away with spicing in a new earth to the cable to the switch which isn't connected directly to the fan motor.