hi all hope someone can shed some light on this for me.
my daughter has a 1999 seicento suite, i.i with air con. it over heated a little recently and the fan wouldn't cut in. i used a paper clip to short the switch on the rad and fan didn't work, so took to auto electrician and he said fan was kaput and switch was faulty , so got another fan (second hand but tested) and a new switch and with the help from peeps on here fitted them, bled the system till a good strong constant flow from bleed and replaced the 30amp fuse.
now if i short the rad sensor switch the fan runs fine but it wont cut in when i run the engine. had thermostat replaced and rad flushed, refilled with coolant and re-bled but still the fan don't work, heater works great, rad heats up evenly and all pipes get hot but the bloody fan wont cut in......what am i missing here? side of rad where switch is gets hot as does all the rad, no smells in expansion chamber and coolant is looking clean and good,so am i an idiot who's missing something obvious, i hope so. any advice would be great. read a few threads but cant seem to find a conclusion.

is it an MPI?
IIRC their fan is ECU controlled

hi, i think its an SPI...it has the square air filter and switch on near side of rad
thanks

cantaffordaferrari said:

now if i short the rad sensor switch the fan runs fine but it wont cut in when i run the engine.

Click to expand...

if thats the case then the rad switch is at fault imo

hi levemircento, that's what i keep coming back to but its a new genuine fiat part..........i know that don't prove its not ..........just that the old switch turns out to be fine. do you know of any other common faults? the only thing left is the pump but i appear to be getting good circulation so kinda ruled that out

Is it boiling over in the expansion tank ? mine was doing the same thing a few weeks ago the head gasket went and it was pressurising the cooling system, fan would not cut in at all, I did the checks on the fan switch etc and it was all working fine yet it would not cut in.

When I had the car in bits I changed the water pump and thermostat and checked both and they were still fine I have kept them as spare in case I need then in a emergency.

If it has over heated then most of the time the gasket fail's pretty much what everyone says here

hi jcdj, had compression test done and head gasket seams fine. it only boils when really hot, about 110 degrees but fan still don't cut in......I'm at a loss as to what else to check.......its witch craft!!!!

Surely it has to be the "new" switch then??
If you short the plug and the fan runs, then the fuse is ok AND the fan is ok

I just read this post again, and sorry, but I misread it
If you short the switch and the fan runs, then it proves the fan, fuse and switch are working. Next step back is the plug to the switch, so it would appear that you have a damaged lead, or something of that nature.

If you short out the plug, does the paperclip glow?

I was stuck with mine it was weird I did the same thing first thing was the fan switch, after that I then started looking at the cooling system on the whole I knew my rad had a small leak also as mine had over heated I thought I may as well do the head gasket which then turned into doing the water pump while were in there and the cam belt, thermostat.

It runs now fan kicks in around 83c never goes over 90c your problem sounds like mine I only found out by sitting in traffic and a puff of steam came out the bonnet I just popped the heater on full and that was enough to keep the car cool while in the jam.

When I got home I checked the car and it was hissing out of the header tank cap till it boiled over

Hi

Put the old switch back, the mechanic who said it was the fan and the switch is a suspect person. Or I have misread your post.

Noel

The fan should come on at 85c approx. the fan is 2 speed, intermittent slow for ac operation, slow constant for 85c operation, full speed for high temp 100?, the overheated one is probably 110c, that one is fitted in the radiator and should not normally operate ever.
There is many parts in the temp control circuit that you could check.
ie
Fuses int the a/c control area
Relays in a/c control area
Temperaure sensor for the ecu, in the block somewhere.
Slow speed series resistor o/c
Looking at the circuit, the fan should come on with a timer when a/c is on, providing the gas pressure is correct and the hi/lo pressure sensors are ok.

I would forget about the overheated operation and concentrate on getting the normal temperature operations going.

Tony.

If you short out the plug, does the paperclip glow?
no, it doesn't glow.......should it?

reddy4bed... Tony, not sure i understand? intermittent for for A/C? the car has a separate fan and circuits for ac. Temp sensor in block? thought cooling side only had sensor on rad and on spi cooling didn't involve ecu.....

JCDJ.... it does sound like same problem, did you ever figure out which element had caused problem? as i have ruled out head gasket by compression test, pump seems fine as have good circulation, thermostat has been changed, switch changed, fan changed and tested, rad flushed and no leaks, system bled.

Noel, am trying that as we speak, car is warming up this very moment, will let you know

Hi mate I think mine was a combination of a leaky rad and head gasket, the car ran fine but as soon as I stop in traffic then it would boil over, it could be a just a very small leak in the HG which will only show up when it gets hot heater matrix could have a leak again try to check that, do you have any idea if it was using water at all, what result were you getting from the pressure test, the guys on here would know if its low or not.

Like I said my car did the same thing and I took the same route, switch first and then so on, if the fan is working when you bridge the connection and you have changed the switch the chances are its something else, pop the switch out and drop it in boiling water see if it triggers the fan that way then you can rule out the switch be sure to have spare boiling water at hand to keep it hot.

Also check the oil for that creamy coffee looking stuff in the filler cap you might be leaking from oil to coolant or the other way around you never know just keep looking.

Just a few idea's again with out looking at it, its very hard to find out the problem we need all the info

Hi. as far as I know, the clip should glow alright. Maybe somebody else can confirm. As far as i understand if that is not glowing, then there is a problem with that lead. It is connected to an earth on the car and from what I remember, the earth is just behind passenger headlight bolted to the car body. Can you check that now and see if its ok?

Just been through all this with my son's car - everything tested ok in isolation but when all wired up it refused to work. Even the harness tested ok for continuity and resistance.

It turned out that the connectors to the switch and fan were bent and were only actually making contact when the connector was twisted or levered slightly by hand. The solution was a wedge of material down the side of the connector to force them back into place.

For reference sticking a multimeter probe into the connector only makes it worse....

Clip should not glow, so thats a good thing.

I'd also be checking the connections as suggested.

Cheers

D

jcdj...dont know exact compression results as this was carried out by the garage that does our mot's, they did it for free ( we have 5 cars we take there for various things) after they had fitted new thermostat, but the guy said in his oppinion head gasket wasnt an issue. have checked oil top and bottom and no discolouration or creaming. car didnt use water......thats not strickly true but about half a litre over two years.

Noel....old switch not worked either,

jimbro1000 said:

Just been through all this with my son's car - everything tested ok in isolation but when all wired up it refused to work. Even the harness tested ok for continuity and resistance.

It turned out that the connectors to the switch and fan were bent and were only actually making contact when the connector was twisted or levered slightly by hand. The solution was a wedge of material down the side of the connector to force them back into place.

For reference sticking a multimeter probe into the connector only makes it worse....

Click to expand...

Thats a very interesting point.......will check that as a matter of some urgency as its most likely the plug on the rad as that's the one that's had the paper clip poked in it so if any damage its likely there, it follows that if switch is OK and fan is then is problem in between ?? so will check and let you know, thanks