Xantia Radiator fans

[Jodyone]

I'm sorry to post with this subject - I get the impression its one of the most common subjects here, yet after reading all I can find here, I'm both more knowledgable and more confused.

Xantia HDi 90: The radiator fans don't start. That's fair enough in one sense, as I don't think the engine has got hot enough yet for them to start- with this weather, and this engine, I can't get the engine hot enough..!

However.. nothing happens when I turn the aircon on either, and the aircon seems to be working: it's hard to judge if it's blowing cold, but it seems to demist fast enough, I can hear a relay clicking, and a brief change in engine pitch, when I press the button. I understand the fans are supposed to run at low speed when the aircon is on, whatever?!

From reading articles here, I tried to locate the temp. sensor, in order to unplug it and hopefully kick the fans into action. I found a plug with a green internal circlip, about 2 inches behind the thermostat but mounted on the thermostat body: is this the temp. sensor? I tried to remove it, but succeeded only in breaking the circlip- the plug is still defiantly attached. Is there a trick..?

Of the three relays between the fans, the top two both have constant 12V at the topmost pins. That is about the extent of my electrical insight- but does it help? I have a multimeter but not a lot of accompanying knowledge- I just use it as a glorified wire+bulb..! The contacts in the bottom (middle) relay are pretty corroded, though I've cleaned them up. I've swapped the three relays around, to no effect.

What's my best course of action: Ignore it -the car isn't overheating, after all- and start worrying in the summer? If there's a problem, I'd rather sort it now however, as I have a little time now that I won't have soon. Or, is there an easy diagnosis/series of checks I can do, to get peace of mind?

Thanks to anybody who can help!

[CitroJim]

The HDi engines don't have the convenient brown sensor (the Bitron) that can be disconnected to test the fans The green one is the engine coolant temperature sensor and is only indirectly responsible for fan control - everything else is under control of the ECU.

I've seen a couple of HDi-engined cars with this problem and yes, they rarely run as the engines are so well cooled and this can be their downfall. They run so infrequently they forget how to!!!

Often they have sticky brushes and as the two fans are wired in series it only takes one to stop working and it stops the other one too. A good test is to engage the aircon to force the fans to start and then poke the fan blades of each with a stick (not your fingers!!!) you may be lucky and find they then start up and run. This is bad/stick brushes.

There's no fix as the motors are sealed units. However I have known a good 'sticking' as described above to get them working happily again - the exercise of running does them good. The odd thing is the last fan you 'sticked' may not be the duff one. One method to determine which is to switch off the fans and watch them run down. The one that takes longest to run down is normally the suspect one as that shows its brushes are making poor contact with the commutator and thus has less friction.

Look too at the relay pins for signs of burning, melting and overheating. A high resistance on the relay base can cause a non-run.

[Jodyone]

Thanks again, Jim. I did try "stick-ing" the fans with the A?C on, but only briefly. I'll have another go, with a bigger stick! (not too big). They spin freely though- is there really no easy way to connect them directly to 12V to test the motors? I don't understand electrical systems enough to try bridging contacts randomly in the relays, for fear that I burn something out (and maybe break something that is in fact working fine...)

Does the fact that they don't come on with the A/C, mean there is definitely a problem?

[CitroJim]

Does the fact that they don't come on with the A/C, mean there is definitely a problem?

Yes, there is definitely a problem but to search it out will take a bit of diagnosis. This is hampered from my point of view by not having the HDi specfiic circuits and I'm not sure how the fans differ from those in earlier cars.

First test is to know if the Aircon compressor clutch engages and if the aircon works? It can be a bit difficult this time of year as the aircon won't engage if the weather is too cold.

If the aircon works then the fans should come on at half-speed when when the aircon is operating.

[Jodyone]

First test is to know if the Aircon compressor clutch engages and if the aircon works? It can be a bit difficult this time of year as the aircon won't engage if the weather is too cold.

That's exactly it. I think I'll try the things you first suggested (stick, contact cleaning), and if that doesn't work, leave it until warmer weather, where an A/C diagnosis is easier. As you say, the engine is very efficient and running without fans at all (worst case scenario) might not be a problem for a long time.

[CitroJim]

Although not directly for the HDi, this website shows the circuitry that operates the fans and in the relay area the circuit will be fully applicable.

The main difference is that the HDi (as far as I know) does not have a separate cooling fan ECU and its functions have been subsumed into the engine ECU.

The page shows how the relays operate to give the two speeds and using this information you should be able to happily bridge the relay bases without blowing anything up to test if the fans themselves are OK.

If you bridge the relay bases so they run at fast speed they're wired in parallel so if only one runs you know the other is faulty and thus you then know why the fans won't run at all at half-speed as they're wired in series.

I just caught your last post before submitting this and yes, you're pretty safe without fans for the next little while. My HDi barely gets to the point of opening the thermostat on my normal journey to work... Just keep an eye on the temperature gauge if it does break out into a heatwave anytime soon and take the necessary care...

Hope that's a help...

[myglaren]

Aircon should still work, mine was running today and it is 0°C.
It should kick in if the temperature is >-5°C.
If you set the ventilation to recirculate you will soon see if it is working as if not there will soon be a load of condensation on the glass.

[Jodyone]

I have seen that article, and had already written it off as terrifying-looking. However, bolstered by your comments, I'm going to dive in, wrinkle up my forehead, overheat my brain, and work it out. I'll get those fans spinning if it's the... Etc.

Myglaren- thanks. I'll try that tomorrow.

[xantia_v6]

Aircon should still work, mine was running today and it is 0°C.
It should kick in if the temperature is >-5°C.
If you set the ventilation to recirculate you will soon see if it is working as if not there will soon be a load of condensation on the glass.

On the Xantia, I think that is +5 degrees, not -5. Mine certainly cuts out at +5, and there wouldn't be much point running it below 0, as below that temperature the air can't carry any significant amount of moisture.

[myglaren]

I have tried it last year a below freezing and it still worked and made a significant difference to the condensation when recirculating to warm the car up faster* - couldn't say the precise temperature though.

*as it did today.

- Afterthought: perhaps it runs at below freezing as the air is being recirculated and is above freezing (outside temperature) while in this mode.
In that case perhaps the rad fans won't operate. Only ever heard mine running once, that I can recall.

[CitroJim]

There's a temperature sensor on the evaporator that prevents the aircon running if there is any danger of the evaporator icing. Also the engine ECU has to 'authorise' the aircon to operate and it won't do that if the temperature is below 5 degrees as you say Mike...

You may be able to 'fool' the system into operating by dragging out the evaporator sensor and warming it. Trouble is you have (on a Xantia) to remove the glovebox...

Steve, I think you may have a problem if your's runs when the brass monkeys have their coats on... Get a Lexia on it as you run the risk of damaging your evaporator through icing...

I have seen that article, and had already written it off as terrifying-looking. However, bolstered by your comments, I'm going to dive in, wrinkle up my forehead, overheat my brain, and work it out. I'll get those fans spinning if it's the... Etc.

Excellent, good on 'yer We're here to help in this quest...

[CitroJim]

I have tried it last year a below freezing and it still worked and made a significant difference to the condensation when recirculating to warm the car up faster* - couldn't say the precise temperature though.

*as it did today.

Ah, maybe the C5 is different and a bit cleverer as recirculated air is likely to be warm enough to prevent the evaporator icing anyway regardless of outside temperature...

[myglaren]

Worth considering Jim but I have run mine all the time since I bought the car and not suffered any problems with it yet.
I knock it off for the first mile or so in cold weather and recirculate the air until it warms up a bit, the put the aircon back on but still recirculate the air until it reaches around 22°C then go to automatic.

When I turned it on today it smelled like an old fridge defrosting, does that sometimes, not often though.

[c.morewood]

On mine you just need the heater fan to max and the heater set to blow on the screen (demist) and the rad fans both come on. If I remember correctly it was the top right relay which caused the problem on mine. I have to be careful when re inserting the relay as the base plate wants to dissapear into the engine bay so that it looks seated correctly when its not.. its a bit fiddly when you've got big fingers!!

[Jodyone]

c.morewood- I'd read that, I think the demist setting is supposed to kick the A/C on regardless, which would explain your account. However, if the A/C itself is faulty, that could result in a misdiagnosis..! I swapped the relays around a few times (I know what you mean about the bendy mounting- working on this car isn't quite like working on my old Merc where everything's practically hewn from granite).

Generally, I've been looking at this (from the article CitroJim linked to):



I think I'm making sense of it. Bridging contacts 3 and 5 (on the diagram) on the left relay (passenger side) should complete the circuit to run the fans at low speed. But- isn't this dependent on a good earth from the right motor? That is, could this be an Earth Problem? I'm more used to classic cars, where electrical issues are usually Earth Problems..