hot Radiator at top, cold at bottom xud7

[white exec]

OK. Two fans, with two speeds, so these will be controlled by
- temp sensor (usually with a brown body or connector) on the thermostat/water outlet housing
- a cluster of three relays, which work together to put the fans into slow speed (fans in series) or fast speed (fans in parallel).

For the two fan arrangement, there is no dropper resistor.
It sounds as if your radiator might have the threaded socket for the thermo-switch (#7), but this isn't fitted, just blanked off, because the sensors on the 'stat housing will be triggering the two speeds instead.

I don't have a circuit diagram for your 205 non-turbo diesel (mfg date: 17 Dec 1993), but someone here may well have. If you have a Haynes manual, it will likely contain the circuit for twin fans.

If your fans are coming on prematurely (presumably at slow speed), it could be that one of the sensors is misbehaving.

[admiral51]

Okay a lot of This will be about A/C but as this is a 1993 Pug at around the same time as the Xantia was first introduced to the market with a similar fan set up it does have some wiring diagrams for how the relays work and also the Brown stat plug.
The link within it also shows that a wiring break can put the fans on at random times but you do need to read it all and see if it relates to your vehicle.

*****Disclaimer*****
The diagrams are for a Citroen Xantia but logic states the operation of the 3 relays set up would be similar as part of the same group

[lad-with-205d]

BIG update

after a full day on the car i've found the fan switch on the rad 3 pin plug (purple ring on it) directly under the feed pipe
and a yellow ringed sensor that had know wires going to it bit had 2 pins, had a good look but couldn't find any wires to plug in to it.
I did however find this

the rad has now been changed and flushed lots as the old one looked like this

but still the fan comes on, even when driving at reasonable speeds, but the hole new rad is hot!!!!
I am stumped!!!!!

For reference the cars fans have never come on before, apart from motorway traffic jams

[white exec]

Very confused now!
Your first photo shows a fan (slow speed) dropper resistance. This is only fitted to cars having a single fan.
You say you have two fans . . . which is it, one fan or two? (Some cars had space for a second fan, but it wasn't factory fitted.)
You also mention a fan switch on the rad, with three terminals. Could you post a photo of this?

We need to clear all this up, in order to determine what cooling fan control system you have.

[xantia_v6]

I still don't see why you are looking for a fault.

The engine produces heat.
The hot water goes to the top of the radiator
The fan switch in the radiator senses the heat and turn the fans on
The fans cool the radiator but the cold water sinks to the bottom.

[Paul-R]

The fifth photograph of the radiator shows that a great many of the fins in between the tubes are missing. This means that even though the hot water may be moving through the tubes I suspect that the heat in them isn't able to be radiated away properly. Even if the radiator tubes have now been cleaned out I think that the radiator needs replacing. You may be able to find a traditional radiator repairer who can replace the core more cheaply but usually a new one is the best answer.

[lad-with-205d]

Very confused now!
Your first photo shows a fan (slow speed) dropper resistance. This is only fitted to cars having a single fan.
You say you have two fans . . . which is it, one fan or two? (Some cars had space for a second fan, but it wasn't factory fitted.)
You also mention a fan switch on the rad, with three terminals. Could you post a photo of this?

We need to clear all this up, in order to determine what cooling fan control system you have.

heres more photos

there are two fans fitted and wired up (see the two white connection plugs)

what i think is the fan switch (looking up from underneath)

heres the one with know plug on it (from above)

and this is a 2 pin plug that when shorted to ground makes the stop light come on in the dash

i've got 2 haynes books for the car one is for the petrol 205 and the other is for the xud engine both have wiring diagrams that don't match up with my car....
Our family has had the car from new so i've got good records of whats been done to the car over the years and cant see any coolent work apart from changing the fluid,

thanks for your help guys it means the world to me

[lad-with-205d]

The fifth photograph of the radiator shows that a great many of the fins in between the tubes are missing. This means that even though the hot water may be moving through the tubes I suspect that the heat in them isn't able to be radiated away properly. Even if the radiator tubes have now been cleaned out I think that the radiator needs replacing. You may be able to find a traditional radiator repairer who can replace the core more cheaply but usually a new one is the best answer.

yer!!!
i fitted a new rad after seeing that mess it was only £45,
still having the same problem with fans coming on in normal conditions so i think it must be a switch or a wire brake triggering them to come on and stay on whilst moving

[lad-with-205d]

I still don't see why you are looking for a fault.

The engine produces heat.
The hot water goes to the top of the radiator
The fan switch in the radiator senses the heat and turn the fans on
The fans cool the radiator but the cold water sinks to the bottom.

hi xantia_v6 i think its a fault because the fans wouldn't cut in before and now they do, on the same journeys, same speeds, same wether ext......
i worry for my little xud as i hear over heating is the biggest killer of xud engines.....
the fact that it was not heating across the hole rad or down to the lower hose made me think it was blocked,
keeping water that would normally flow through the rad stuck on the side of the rad with the fan switch coursing it to trigger sooner

i hope you under stand
matt

[white exec]

OK, here goes. Thanks for posting the photos.

You seem to have two fans and a thermo-switch, so must also have a bank of three relays (working together) to control the cooling fans.

The relays comprise three identical-looking 'cube' type. Two of them have 4 pins (and 4 connections on the socket), and the third has 5-pins. Important that the 5-pin one goes in the correct 5-pin socket. All three must be present, as they work together.

There look to be two switches screwed into the radiator side tank, one yellow, one purple.
Not sure which is which, but the thermo-switch that controls the fans will have 3 wires connected to it, and will usually be half-way down (or maybe lower) on the side tank.
The 3 wires are
- Supply (or Gnd, depending on the build of the car)
- power (or Gnd) out to the relays, to trigger Low fan speed *
- power (or Gnd) out to the relays, to trigger High fan speed *

If the fans are cutting in at too low a temperature, it is likely that the thermo-switch is faulty, and should be replaced.
* From parts info, the two stage thermo-switch† should operate at these temperatures:
Low speed cuts in at 97°C, cuts back out at 92°C
High speed cuts in at 101°C, cuts back out at 96°C
These temperatures are those at the thermo-switch itself, and not necessarily those at the dash gauge.
† Pt.no. 1264 44, now NFP.

The other switch screwed in, if near the top of the rad side tank is probably a Low Coolant Level warning switch. It will have just two wires/pins, and if unplugged (engine running) should throw up a warning on the dash, and possibly a STOP warning too.

You may or may not have a coolant header/expansion tank. If you do, the header tank will be fitted with the system's pressure cap, and the radiator will either have no cap at all, or else a blank one.

For the latter - no separate expansion/header tank - the radiator side tanks are used as coolant reservoir, and the radiator runs with an air gap (usually 5cm or so) at the top, to allow for coolant expansion. In this case, it is essential that coolant level is decently maintained, hence the level warning sensor/switch.

The XUD is an amazingly tough engine, but its cylinder head does not like the presence of trapped air in the head, which can cause hot-spots, localised boiling and coolant loss, and head gasket troubles. Important, therefore, on these engines to bleed the cooling system properly (at the bleed screws) and maintain the level . . . especially where there isn't a separate header/expansion tank.

Finally, to reinforce Mike's point, it is normal for a radiator to feel hot at the top, and much cooler lower down - the more so if the fan(s) have been running. Hot water enters at the top, gets cooled, and falls to the bottom, aided by the pump. After starting a cold engine, and until the thermostat opens, the whole of the radiator will feel cold. As the 'stat begins to open, hot water will flow into the radiator top, and it will take a good few minutes of further running before it reaches the bottom of the rad. With a diesel left to idle, it might take 20-30 minutes for the whole system to get up to proper full running temp (c. 90°C) and the fans cutting in at slow speed. These diesels are incredibly frugal with fuel, especially at idle!

[ksanturion10]

Wow, I've guessed .
So it is an analog 2 speed system - nice

[white exec]

Electro-mechanical to the core! Yipee!

[lad-with-205d]

Electro-mechanical to the core! Yipee!

This looks to be the headlight dim-dip resistor (i don't know how it works)

took me lots of head scratching and i think i understand what you mean finally.......... (yes i'm slow)
I can see the 3 relays and have a new Temperature switch coming so if that fails i'll look at relays

I do under stand i my be chasing a problem thats not a problem, but i'm getting to grips with car repairs atm so i'm not to worried about the wasted time and money i'm chucking at it

[myglaren]

Phased out years ago. If you just put the side lights on, that would bring the dipped headlights on at half brightness to stop people driving around with just sidelights on.

[admiral51]

i've got 2 haynes books for the car

Finally the problem of lack of toilet roll has been resolved

Seriously glad to see you are making progress and atleast here nothing is rationed