Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

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white exec
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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by white exec »

WTCU = water temperature control unit - the name used on earlier models.
It's #1320 in the diagram above, and called 'Engine Test ECU' on the components list.

For safety, do any testing with a 30amp fuse in the line, if coming straight off battery.

wheeler
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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by wheeler »

1320 is the main injection ECU, this is what switches the low & high speeds on this system. The mid speed is switched by the A/C system.

I know what you mean now, the 15 pin black box under the N/S headlamp on old Xantia's? I just always referred to it as the 'Bitron Box' after the manufacturer.

And yes protect the jumper wire with a fuse or a power probe with built in circuit breaker.

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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by white exec »

Thanks for posting that clearer screen-shot circuit diagram.

Have printed it out, and studied how it works.

System is described as "two speed" in the components listing, and this is so, but there's also a 3rd speed of fan operation, which kicks in when the AC operates.

Low fan speed
Coolant temp sensor (#1220) triggers ECU to make line 1550 go to Gnd.
RLA #1508 switches on.
Brings +12 power from fuse F2 to Dropper Resistor #1506, and to Motor #1510, then to Gnd.
Fan runs at Low speed.

High fan speed
Sensor triggers ECU to make line 1540 go to Gnd.
RLA #1509 switches on.
Brings +12 power from fuse F3 direct to Motor, then to Gnd.
Fan runs on full 12v, at High speed.
This 12v supply is also fed to line 1512 on the ECU. Not sure of the purpose of this, but could be an instruction to the ECU to increase fuelling at idle, to maintain/increase engine revs, in part to provide additional alternator output. Unsure about this.

AC switched on
When pressostat #8007 outputs a +12 signal, RLA #1514 switches on.
This allows both of the dropper resistances (#1506 & 1519) to operate I think in parallel, providing a dropped voltage (but probably greater than Low speed) to the Motor.
>> Now, ???, this power has to come from somewhere, and it looks to me that it can only come from RLA 1508 (and fuse F2) being switched on, so line 1550 must be Gnd'd too (just like slow speed). I presume the ECU again looks at line 1512, and switches on RLA 1508.

That's how I read the circuit operation.
The system contains 3 relays, but its operation is entirely different to the classic triple-relay arrangement for twin-fan vehicles.

Hope helpful.

wheeler
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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by wheeler »

Yes that’s about it, the main difference between the triple relay twin fan set up is the 2 fan motors get connected in series To create the slower speed.

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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by Fartblast »

Hi and many thanks again for all your help and input. I just removed the fan (had to cut the two wires) and connected it to the battery and it works. Will solder the wires when I re-fit. I am thinking of just replacing the three relays as do not know how to test them.

Could the engine temperature sender unit be one of the causes, although the dash temperature gauge works OK, is there a way to test it and where would I find it.

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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by Fartblast »

The relays are 12v - 35a 03531 G Cartier. Is there a way to test them.

... YT I guess.

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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by white exec »

The relays will be standard automotive 12v 30/40A "cube" type, with 0.25" base blades.
One of them (#1509) needs to be a 5-pin (changeover) type, and in the correct (5-contact wired) socket; the other two are just 4-pin (make).
To keep things simple, just buy three 5-pin types, then it doesn't matter which goes where.
Obtainable from any good motor factor or electronics store, or Amazon etc.

Testing...
base contacts:
85 & 86 are the 12v actuating coil
30 is Common
87 is Normally Open (makes with 30 when coil is powered)
87a is Normally Closed (breaks from 30 when coil is powered) - only present on the 5-pin version
Top cover usually separates from base when levered off, to get to internals.
Clean internal contacts with glasspaper/emery board. Expect see some arcing damage in heavy-duty applications like this one.
Google "automotive relay contacts > images" for piccies.

Clean up base blade contacts and the sockets too.

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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by wheeler »

The point here is if you power up pin 3 of one of the resistor plugs (with both disconnected) the fan motor should operate even if all the relays are unplugged, unless im reading the diagram wrong ??
This suggests to me that the problem is downstream of the resistors. We know the fan motor works so this suggests to me the motor is either missing its earth or there is an open circuit/ high resistance on the wire that supplies it from the reistor.
The weakest link here is one of the splices (E151)
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white exec
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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by white exec »

" The point here is if you power up pin 3 of one of the resistor plugs (with both disconnected) the fan motor should operate even if all the relays are unplugged, unless im reading the diagram wrong ?? "

That's correct.

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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by Fartblast »

I have reconnected the fan using a block connector and as before I tested it with a direct live feed from the battery to number 3 terminal on the relay plug and the fan worked. I tried this a couple of times waiting the for fan to stop each time but on the third attempt the fan would not turn. I tried it again several times but nothing.

I then started the engine to get it warm. I say warm as its cold working outside so I doubt if I can get it hot enough for the fan to work anyway. However I then pressed the AC button and could hear the clutch kick in as usual and to my surprise the fan was working. However moments later I tried the AC again and the fan would not work, so I moved the fan with my finger and it started to work and kept going until I turned the AC off. I'm wondering if the fan motor is weak/faulty or could the reason be there is not enough voltage getting to the fan.

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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by white exec »

1. Try that test of powering up the fan by direct connection, not to term3 of the resistor connector, but direct to Battery+. If the motor still starts intermittently, the fan motor is faulty
– either mechanically stiff:
With everything switched off, try very gently turning it with a light finger pressure; there should be no stiffness
–- or the motor brushes are worn, and need replacing:
Involves removing the fan and opening it up. Sometimes repairable (a clean up and new aftermarket brushes, and the bearings oiled), or else a replacement motor.

If you do replace the fan, it's important you get the right one, with the correct part number**. There were a large number of different types and powers of fans (from 120W to 310W), and you need the right one to work properly with those two dropper resistances.

2. If motor checks out ok (direct from battery), suspect the rest of the circuit, and proceed with this...

Test the rest of the circuit for correct operation by disconnecting the fan, and temporarily replacing it with a 55W headlight bulb (or better still, two in parallel, i.e. a 110W load). If you operate the AC (for instance), the bulb(s) should go on and off cleanly. Disconnecting the temp sensor should also bring the bulbs on.

But clean up the relay contacts, though, and test again, as above.
In that circuit there are only relay contacts and the two dropper resistances, so not too much to check.

** If you need the fan part number and details, we can post those for you, but you'll need to make a parts-info donation to the forum (which will cover you for this year and next)...
A response to your question will require detailed vehicle information that requires you to have made a current contribution to the Forum.
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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by Fartblast »

When I removed the fan I could not feel any stiffness and it spun freely. I also connected it directly to the battery and it seemed to work OK, although did appear to pick up speed slower than I was expecting. Should it spin fast instantly? I will take a look at the relays and give them a clean. I Also disconnected the temp sensor and the fan did not operate, but it sent the dash guage to maximum. When repalced it returned to the normal two bars.

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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by white exec »

The dash gauge normally has its own temp sender, so you probably pulled that one.
There is usually a second sender, which signals to Injection and Cooling - this is the one to disconnect.

Applying battery voltage direct to the fan motor should get it spinning to full speed with 2-3 seconds. A limp or gradual start suggests it has brush problems, unable to deliver full current to the rotating armature.

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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by xantia_v6 »

As a fairly easy test, you could connect a small 12V light bulb in parallel across the fan supply wires (where you cut them?), with the fan still connected, and if the light comes on, but the fan does not spin, then you know that the problem is in the fan motor.

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Re: Radiator Fan NOT Working Xsara Picasso 1.8sx 2003

Post by admiral51 »

Well done on getting this far with it.
Just for clarity ( for myself ) you say you have put a 12v feed direct to the fan, have you done this by removing the plug on the back of the fan or by tapping into the loom where you cut it?
It could be the plug/connector on the back of the fan not making good contact?