Cooling Fans not coming on.

[McNasty]

Hi All,
Could anyone point me in the right direction please. I am in the process of preping my Cerb for Les Mans and discovered that my cooling fans are not switching on. I have put in a temporary direct fused supply from the battery and proved that the fans are working, however after unpluging them and reconnecting them they came on automatically at about 95 deg as normal, so i though it was just the connectors. Alas they have stopped working automatically again. I have checked the fuses and they are both ok, any ideas what to check next? is there a thermostat, if so where can it be found?
Many thanks in advance.
Andy

[Mad Mark]

Have you checked the Temp sensors? there are two. One is mechanical capillary type which operates the temp gauge the other electrical that goes to the ECU and controls the fans. Usually if its faulty the fans will switch to on in a default safety mode but still worth checking.

[McNasty]

Thanks Mark,
I got stuck in traffic and the temperature went to the end of the scale with no fans coming on at all. i.e. no default. where are the temperature sensors, is one of them located next to the point where the capilary comes out of the pipework?

[Steve_T]

In the plumbing under the front cover you'll find the temp sender for the ECU, this is what you need to replace if cleaning up the contacts is not enough. The ECU grounds the fan relays to switch the fans on.

[McNasty]

Thanks Steve
when you say grounds the fans, i take it you mean earth them. when i wired up the temporary switch i used a scotch lock connector for each fan onto the coloured wires of the two fans (one red and one blue)assuming the black on both were the negative (or earth). this meant that the when the connectors from the wiring loom was connected in the normal manor the fans were earthed in the usual way again proving that the connectors were ok on the earthing side. would i be right in thinking that the relay's switch on the live side?

[JensenA]

Bleed the cooling system first. Air in the sytem will definitely prevent the fans coming on.

[McNasty]

Thanks JensenA
Just noticed what seems to be a weep in one of the metal to rubber connections on the cooling system pipework below the breather from the drivers side rocker cover. i am hoping that the oil is from the breather pipe and not the cooling pipe!

[Allandwf]

The Temperature sender for the ecu is in the water rail behind the steering rack, under the F1 panel. Just below the wash bottle. If you disconnect it the fans should come on.

[Steve_T]

McNasty said:

Thanks Steve
when you say grounds the fans, i take it you mean earth them. when i wired up the temporary switch i used a scotch lock connector for each fan onto the coloured wires of the two fans (one red and one blue)assuming the black on both were the negative (or earth). this meant that the when the connectors from the wiring loom was connected in the normal manor the fans were earthed in the usual way again proving that the connectors were ok on the earthing side. would i be right in thinking that the relay's switch on the live side?

The fan relays are connected to +12v on one side and to the ECU on the other. The ECU switches the fans on by completing the circuit to ground (battery -ve).

[McNasty]

Thanks Allandwf,
I have disconnected the sensor (on the other side on my car) from the the wiring and the fans do come on as you suggested. So does this mean that the ECU is ok or perhaps the sensor is faulty? Assuming that there is no airlock of course. I will look into this tonight.

[McNasty]

thanks everyone, seems like i have a bit of a dodgy connector on the sensor, i wiggled it a few times and all seems to be well. just needs cleaning allthough it did seam moist, maybe DW40 residue from the recent service.

[gruffalo]

The pipe that the sensor is mounted in is prone to rusting and the first sign is ofter a weeping leak near the sensor, worth keeping an eye on that.

[ridds]

McNasty said:

thanks everyone, seems like i have a bit of a dodgy connector on the sensor, i wiggled it a few times and all seems to be well. just needs cleaning allthough it did seam moist, maybe DW40 residue from the recent service.

This is one thing that really worries me about the Cerb ECU and electrics. Sensor failure results in fans on fully, dodgy connection results in NO fans and NO MIL.... very dangerous as you have found.

[C3BER]

ridds said:

This is one thing that really worries me about the Cerb ECU and electrics. Sensor failure results in fans on fully, dodgy connection results in NO fans and NO MIL.... very dangerous as you have found.

This is exactly what I had but with an added bonus of a faulty temp sensor. I went through every combination of possible reasons why sometimes I would boil the water and sometimes not. Sometimes fans on sometimes not and sometimes the laptop said yes and sometimes it would say bloody no. Sometimes cerbs can be so frustrating :-) well sometimes.

[Marpug]

Had exactly the same with mine but after replacing the temps connector( connector and pins ) still had the issue and is wasn't until I had replaced the temp switch for the second time!( both replacements were new ) it was fixed.... bottomline if you still have the same issue after you have cleaned up the conntacts and if you get a problem when you wiggle the connector.. go for a new sensor....

FYI ...
If you are handy with a soldering iron you can get replacement pins for the connector here.... ( pins you want are 0.35-1mm)


http://www.polevolt.co.uk/acatalog/Timer_Connector...