overheat warning fan not running

Hello this is my first post but ive been looking in getting advice for a while now but can seem to find a definative answer
My wife's 03 1.4 petrol c3 has a strange problem
It's giving overheat warning but the cooling fan not running although sometimes it does come on but not until after overheat warning comes on
I have a obd2 reader so I've watched the temp from the ecu and it seems the warning comes on around 97°-98° (is this right? Seems low to me)
it jumps suddenly from 3 bars on the dash to all bars (surely this isn't right?)
I've read a fair few post about this kind of problem and see that the temp sensor,thermostat and air lock are the common problems for overheat but it's seems my fans not running when it should be is there any way to trick the fan to come on to test for loose connections cos like I say sometimes it does come on but most times it dosent
any recommendations would be greatly appreciated

Hi gfromleeds, welcome to the forum.

gfromleeds wrote:I've read a fair few post about this kind of problem and see that the temp sensor,thermostat and air lock are the common problems for overheat but it's seems my fans not running when it should be is there any way to trick the fan to come on to test for loose connections cos like I say sometimes it does come on but most times it dosent
any recommendations would be greatly appreciated

Its a common problem and sometimes faulted down to the engine ECU after all the other parts are found to be ok

You can put the fan in test mode and get it to run and run a different speeds if its a multi speed fan by using the lexia tool for Citroen which will test more of the fan system than just putting 12v on the fan terminals.

Some of the petrols have two temperature sensors, one for the ECU and one for the dashboard display, so make sure how many sensors you have and look at the right one.

gfromleeds wrote:I have a obd2 reader so I've watched the temp from the ecu and it seems the warning comes on around 97°-98° (is this right? Seems low to me)

The thermostat opens at 89°C , so overheat warning at 97°-98°C sounds ok to me. There is some configuration in lexia for overheat warning..... I will dig it out for you....

C3driver52 wrote:so overheat warning at 97°-98°C sounds ok to me.

No, the fan comes in at 97°-98°C and the warning is 118°C

I didn't find the configuration I was looking for, but I did find some help on the cooling configuration in the engine ECU.

C3driver52 wrote:

C3driver52 wrote:so overheat warning at 97°-98°C sounds ok to me.

No, the fan comes in at 97°-98°C and the warning is 118°C

I've been shutting down as soon as the warning comes on So not let it go above 98-99°
So is it possible if I let it warm for a minute longer (so it goes enough above the 97-98°c allowing for 2/3°c veriance) the fan WILL come on?
I just don't want to cook it!
Just thinking if the fan and dash display are different senders. could it just be a faulty dash sender and I'm not letting it get warm enough for the fan?
Where are the 2 senders if it has them?
The fan has 5 wires if that helps
2 thick ones and 3 very thin ones

gfromleeds wrote:Just thinking if the fan and dash display are different senders. could it just be a faulty dash sender and I'm not letting it get warm enough for the fan?

Could be, one is faulty and one is OK?

gfromleeds wrote:The fan has 5 wires if that helps
2 thick ones and 3 very thin ones

Its a multi speed fan controlled by the engine ECU.

questions-about-a-petrol-powered-citroe ... -t400.html

gfromleeds wrote:Where are the 2 senders if it has them?

One is on the coolant outlet near the thermostat and the other is attached to the head.

Thermostat one


citroen-c3-questions/temperature-gauge- ... 46-10.html

The cylinder head temperature sensor on a Citroen C3
There are lot of different sensor for the temperature used over the years and models of the C3 you should be able to pin down the right ones by using the vehicle selector on the euro car parts website.

C3driver52 wrote:

gfromleeds wrote:Just thinking if the fan and dash display are different senders. could it just be a faulty dash sender and I'm not letting it get warm enough for the fan?

Could be, one is faulty and one is OK?

gfromleeds wrote:The fan has 5 wires if that helps
2 thick ones and 3 very thin ones

Its a multi speed fan controlled by the engine ECU.

Citroen C3 radiator cooling fan connector in engine bat

questions-about-a-petrol-powered-citroe ... -t400.html

gfromleeds wrote:Where are the 2 senders if it has them?

One is on the coolant outlet near the thermostat and the other is attached to the head.

Thermostat one


citroen-c3-questions/temperature-gauge- ... 46-10.html

The cylinder head temperature sensor on a Citroen C3



There are lot of different sensor for the temperature used over the years and models of the C3 you should be able to pin down the right ones by using the vehicle selector on the euro car parts website.

Nice one cheers
Any way to test them or is it just worth getting a new one?
Would I be safe letting it heat up to say 105°c to see if the fan does come on?

I've run it up to 90° according to the obd2
Unplugged sender near the thermostat and according to the obd2 the temp dropped to -40° but the dash gave a overheat warning and the fan started up
Plugged it back in and everything went back to normal and fan stoped
Ran it at high revs to build the temp up and the fan came on at 97°and cooled it to 95° then stoped
Repeated this a few times and it seems ok now!
Errm confused don't cover it!
I'm thinking a loose wire/ bad connection somewhere?
I've sprayed contact cleaner in all the plug I could get to so we shall see what happens
I'm gonna run it for a few days because I can keep an eye on the temp in real time with my reader so will post back in a few days!
Wish me luck

gfromleeds wrote:I'm thinking a loose wire/ bad connection somewhere?

This is not the first time there has been a high resistance on the plug/socket connection on the C3 (but not the same sensor). Unplugging and replugging fixes the problem

This one was for the TPS, fault showing and apparent, unplugging fixed it questions-about-a-petrol-powered-citroe ... t1133.html

gfromleeds wrote:I'm gonna run it for a few days because I can keep an eye on the temp in real time with my reader so will post back in a few days!
Wish me luck

Good Luck and thanks for the update and future updates

Well as promised an update
I've been using it for the last few days and everything seems ok
5 miles stop start city driving followed by 10 miles motorway twice a day and the temp never went above 3 bars on the dash
So guessing was just a bad connection that's now clear
I did however in my trying to find the problem drop the water from the radiator as it look a bit manky
Now I read that the C3 holds 7 litres but only 2or3 came out
how would I get the rest out to do a complete flush?