As tiitle car is a SIERRA SAPPHIRE 2000E fans were working day before yesterday, then yesterday the temp started to creep up past the N I pulled over n checked the fans and,the fans were not running I've checked wiring all seems ok fuse is ok, I not sure about relay or switch as I do not know how to check? any help would be much appreciated

Wes

 

Not sure on standard sierras but in cossie is common for terminal to melt inside fusebox and fall off the fuse, you really need to see if you have live to the fans then check the earth before the switch, then a simple test is to bridge the wires in the switch, if this works then the switch is faulty. Shouldn't take long to trace the fault as not much to them really.

 

Disconnect the plug from the fan switch on the radiator, shorth out the connections on the plug and it should switch the fans on, if it does it's just the fan switch that needs replaced, if not then problem elsewhere.
If it's twin fans and there both not woring it's unlikely to be the motor, it's likely a wiring fault somewhere.

 

As said remove the connector from the switch and bridge the wires, this SHOULD start the fans, if it does not then the switch can be eliminated. (Do this test with the ignition on as it may be a switched live)

I would then look toward the relay, that being a yellow square one.

Martin

 

Lesser models are fine, the problem with the Cosworth is the fans were never designed properly.

The sole problem of the fuse melting is due to the totally inappropiate switch that is fitted as standard which in turn causes the fans to stay on for far to long=melting the fuse, that along, the standard wiring isn't really upto scratch either, hence why they should be rewired!

Martin

 

Right I've checked relay and fuses all ok, changed switches still same problem so i removed plug from fan switch and looped the connections fans kicked in straight away. so does that rule out the wiring? what could it be causing it they were ok last week. For time being I have wired to a switch not sure if this is right or not so ready to be corrected: on fan switch plug there are 4 wires (red/black, blue/black, black, black) ive run live from switch to red/black, earth to red/black and switch live to black fans work and fan switch lights up as it should but if i 've wired wrong i would like to correct!

cheers

 

Fan switch mate.

 

Ive replaced fan switch still same problem thats why i wired fans to a switch but its not ideal solution would rather fix problem

 

are you SURE the temp is getting hot enough to turn the fans on?

the standard gauge tells you next to nothing AND you've said it's sitting within the NORM.

the fans only come on when the car gets very hot

 

After i replaced fan switch and temp sensor i allowed car to run The temp gauge went above the N and fans still hadnt kicked in and header tank was boiling the water

 

well you proved all of the wiring was fine and replaced the fan switch so you have one of 2 issues:

1) the brand new fan switch you got is also faulty
2) you have a mechanical cooling problem ie an airlock or a blockage somewhere.

if you say the coolant had boiled over have you properly bled the system so you are SURE there are no airlocks in it?

 

I fitted a fan switch a month ago, it lasted 2 days, replaced it for another been fine ever since so new parts can be faulty

 

If it's a four pin switch then that means you have dual speed fans or individual control of each fan.

It may be you have a partially blocked rad which I would think is unlikely as you would notice it elsewhere, thus the switch not working as the coolant temperature is never reaching the switch, IF you have a rad switch, i.e. it's not located in the thermistat housing as all models differed, other than that, as said, the only other thing can be a bad switch.

It should only be until you get it working properly, having fans on a switch is never a good idea, say you forget to switch them on etc, plus you cannot activate them at the correct temperature like the switch. It's an automated system for a reason!

Your wiring dosen't make sense, the switch just completes the GROUND circuit for the relay, so you shoulden't have to be running lives anywhere, so have you wired direct to the switch plug, or the fan connector(s)?

Martin