I have recently bought a sapphire cosworth and the engine fans do not work. I have replaced the wiring harness and radiator fan switch. When I bypass the radiator switch the fans work, they do not come on however when the car is running and gets hot.

Does anyone have any idea how to fix / diagnose this, I'm tempted just to buy an override switch but I'd prefer to fix the problem properly.

 

If bridging the switch works, then it cant be the switch or the fans themselves. You need to recheck your wiring

 

The wiring would appear to be fine, depending on what you mean by 'bypass' the switch, I guess you mean bridge the connector?

The standard switch (red) closes at 86°C which is to early, in addition it keeps them on for too long.

For this reason a "uprated" switch is available (merely closes later and runs the fans for a shorter cycle)

As your new to them, the fuel pump wiring can build resistance, thus the pump cannot draw the current it needs under load, which can lead to a meltdown!

The solution is to rewire the pump, both of these are common problems.

They are automated for a reason, so no, don't be temped to add a switch.

Martin

 

Yeah, I've got a feeling i need to recheck my wiring, i assumed that because the fans come on when i bridge the switch that i had got it right. Ive got an updated switch, at what point on the NORM should the fans come on, ive only been letting mine run up to the bottom of the N?

 

The wirings fine then.

I think you are expecting them to come on early, I would leave it a little longer to see if they come on...

Martin

 

Hopefully that's it then, i think i read somewhere that the fans are supposed to come on at the top of R so i assumed something was wrong, cheers for the advice. Yeah the fuel pump rewire's on my list, is it relatively easy to do?

 

The normal fan switch on mine comes on around the top of the 'O'

As said above if you've fitted an uprated switch they don't close until over 90°C, standard is around 82°C

I've got a normal switch in mine and it cools it down within 1-2 minutes, I did have an uprated one in and the car was red hot all the time, fans not coming on until near the top of the 'N'

Having said all that, the temp gauges are not accurate anyway, I swapped my clocks out when the fuel gauge packed up and it sit's in a difference position's to the old one

 

Right i think that's probably cleared this one up then, i notice you said you USED to have an updated switch, do you think the car runs a bit too hot with an uprated switch and standard rad?

 

In my opinion yes, I was not comfortable with it always being mega hot, then fans coming on and off for a very short period of time, seemed pointless to me.

I put a genuine Ford standard one in and it runs fine, fans come on when it gets mega hot and the fan cycle is around 1-2 mins and then it stays at running temp for ages before fans come in again.

I have a fan rewire loom,pro alloy rad, spall slim fans and a pro alloy 500 cooler and I don't suffer alloy heat soak either

 

The fans were not designed for the car to start with. I have an uprated one, as the standard one used to stay on for far too long, indefinitely in some cases, this is what leads to the fuse melting etc.

Martin

 

Agreed.....mine is fine though. My mate had a saff and the fans were on more than they were off, it was crap. The fans just couldn't cool the car down

 

I have the standard fans and find them fine, I was referring to the switch, which is the problem.

Martin