Radiator fan not working C4

[Fake Concern]

In February, I had a problem with the rad fan working as it should on slow speed & when fast speed was needed I got the message "Stop! Engine temperature too high". I replaced the fan control unit, which fixed it.
Yesterday I got in a traffic jam & the fan didn't come on at all. I left it idling at home and again the fan does not come on at all. The temp guage goes up as it should and I get the warning message.
I read somewhere that disconecting the temp sensor should put the fan on, so I tried it & no fan.
I have also read that when the air con is on the fan should be on, but it isn't, however the air con is not as cold as it should be, but thought it needed re gas.
Questions, is there an easy way to test the fan?
Should I replace the temp sensor to rule it out?
Is it likely the fan has failed?
Is it likely the new fan control unit has failed?
I know there are not many C4s on the forum, but it must be similar to other Citroens such as the C5 (and of course Peugeots)
Thanks for any advice

[Lighty]

In my experience, when the fan control unit fails on a C4, (unit behind front grille) the fans tend to run on for ages after the car is switched off, to the point of flattening the battery.
If your fans do not work at all, I would check first of all that the motor is not seized (just try and turn it manually). Next step would be to check the Maxi fuses under the main underbonnet fuse box.There are quite a few different set ups for C4,s, so its hard to be exact, but that is a good place to start. I have a Power probe tool, so it is easy to power up the fan itself and see if the motor is still good.
If the fan doesn't work, the A/C will be none existent at idle, because the condenser heats up in seconds, so the high pressure in the A/C will rocket upwards, and the system will switch off, the fan should operate at least every 20 seconds when the A/C is on.
The underbonnet fuse box is a weak point on C4.s I have changed several, for various reasons, this could also be the culprit.
If you had Lexia it would help, as you could try and activate the fans with it, but I doubt they would operate.Early cars have the fan control unit built into the actual fan motor itself.
hope some of this makes sense.

[Fake Concern]

Thanks for the reply.
This morning I went to local Citroen Dealer Wilmoth's of Hastings to get a temp sensor and the parts chap was very helpful, to the point of asking a mechanic! He said mostly what you have said, that most common problem was fan control unit (resister pack). He said sometimes was the sensor, but usually the push in one (mine is screw in). He said failed fan is not very common & maxi fuse only likely to have failed if other major problems have taken place such as seized fan (it's not you can turn it). He also said (like you) that Lexia is the best option for checking it.
I fitted the temp sensor, still not working. I took all the connections to the fan & control unit apart & sprayed with contact cleaner (not working still). I tried to test if I had power at the fan, but laying on my back sticking wires to a boot lamp (!) into the connector may not have been the most reliable test as I got no light, but doesn't mean there was no power.
I think think the fuse box looks good not wet or corroded that I can see anyway. Hope it's not that.
Now I have read your answer I will have a look at the maxi fuses. Do I need to take the fuse box right out to get to it? I take it I can get a spare maxi fuse from Eurocarparts or Halfords?
If I still have no joy I shall have to see if anyone near can help me with Lexia.
Once again thanks for your answer, if I don't get

[Fake Concern]

Now I have removed the maxi fuse (not blown) & cleaned terminals, cleaned every connection I can find & still no joy. The schematic I have shows a relay in the glove box fuse box, so if I can work out which one, I will replace that. After that out of ideas. I still don't really know how I can try the fan apart from taking a flying lead from the battery to it. Lucky the car has to sit idling for quite a long time before the temperature goes up!

[Fake Concern]

Have been hooked up to Lexia & found no faults for the rad fan (thanks again Malcolm).
Does any one have any more ideas where to go next?
Does any one know where (if) the fan relay is?

[wheeler]

Were you able to actuate the fan with Lexia ?

EDIT: Just saw your other post.

[Fake Concern]

Thought I'd better finish this thread; was the radiator fan motor.
Now fixed!

[citronut]

good to here your sorted Peter

[Cutac]

I have the same problems as you do. How hard is it to replace the fan? Does the bumper need to go down?

[Fake Concern]

You can reach the relay through the plastic slam panel, but for the fan motor (which was the problem) the bumper must come off

[Cutac]

Thanks!
I've tried reaching my arm from the bottom and I might just make it with the bumper on

[Cutac]

One more question.
ServiceBox says I need 1253 K2 fan. My friend has a brand new Valeo 1253 K4 which he's willing to sell to me for a nice price, but I'm not sure it'd fit.
Does anybody know what are the differences between the two fans?

[Rosanbo]

Take your fan off, and compare it with friend.

This website says they are the same part.
https://www.autodoc.co.uk/car-parts/oem/1253k2

[Cutac]

It's just that his fan doesn't have the shroud with bolt holes. Seems like I'll be ordering a Hella fan.

[Cutac]

Just to update, it would fit if one would modify the bracket a bit. I couldn't have been bothered so I ordered a correct one.