Engine bay cooling fan

Guys

Since fitting the Emerald, the engine bay cooling fan has been disabled. This is a common issue as the Emerald needs extra wiring adding to the standard loom. My question is if the engine bay fan can be triggered along with the standard Rad fan since its when the car is stationary the engine bay temp climbs. Can i just link the power to fan direct to rad fan at the fuse box, or is there a more elegant solution that keeps the fan going on a timer to clear the engine compartment of hot air? I also considered a manual switch on the dash but ideally want something linked to Temp.

Thanks in advance

Tourbillon

On the later TF's the information for the engine bay cooling fan comes from the same input to the ECU for the rad fan (engine temp sender) however there are 2 separate outputs from the ECU; one to the rad fan relay and one for the engine bay relay "both ground signals" they both come on at the same time (when the temp sender reaches about 104c but the rad fan cuts out at about 96c and the bay fan keeps running for about 5 minutes after that.

Also if you switch off the ignition when the fans are running the rad fan stops as it's main power feed is via the ignition switch (plus you don't need the rad fan running if the water is not circulating) but the bay fan runs on for about 5 minutes as it's main power to the relay is permanently fed (this is a good set-up as when you leave the car when it's hot and there is no air circulation the fan runs on to remove latent heat)

So it would be a compromise to run both the rad and bay fan from the same source; but it would work.

“Just had a quick look at the F wiring diagram and you bay fan relay has a permanent feed so you can share the same relay trigger information from the rad fan relay (ECU sends a ground signal to the relay) and if you could wire in an timer off delay giving an extended 5 minutes after the ECU signal is off then it would work as the later TF’s”

Badger,

Thanks for this, I have looked for a delay timer but not found anything suitable yet. As you state, wiring the 2 together would be a good compromise, I assume i just join the engine bay fan power to the Rad fan relay.

TB

The trouble with running the engine bay fan off the radiator fan circuit is that the radiator fans only become active when the coolant temp is hot, not when the residual heat in the engine bay builds up.
Here is what you need: Davies-Craig Thermal Switch Kit

Your quick fix is to remove the feed at the bay fan relay on terminal 86 (this is a ground feed from the ECU which is no longer sending information due to the Emerald upgrade) and tap into rad fan relay on terminal 86 (this is a ground feed from the ECU when the temp reaches around 102c) so you have connected both relay coils in parallel. Now when the signal comes to switch on the rad fan the bay fan will also run.

The down side is on the F the rad fan relay is under the bonnet and the bay fan relay is under the dash so you will have to route the cable through the bulkhead.

The power feed side is left as original you are only modifying the relay trigger circuit and if Emerald get a fix for the problem just remove your link wire and re-connect the original ECU feed back to terminal 86 of the bay fan relay.

The circuit diagram for the fans is on page 39.2 of the PDF on the downloads section.

Let me have a think about the timer off delay.

Brian.

Our later TF has the bay fan coming on with the rad fans.

Not yet blown up/HGF'd/increased world famine/ accelerated global warming etc.
well, not much anyway.

If paranoid about engine bay temp, why not wire the bay fan to run continuously while the engine is running? Simple job with a relay feed via ignition switch. If ultra-paranoid, wire in a timer so it runs on for 5 minutes after the engine is turned off.

Thanks Cobber, just have to look for something think that in the UK. In the meantime I will go with a wiring like Badger suggested as a stop gap.

TB

Brian

thanks for this, sound like a stop gap until i can source a timer or get a fix using the Emerald.

N

I believe Davies-Craig have a UK agent.
Their stuff is good quality, I've been using it for years, in fact when my family had a racing team back in the early 70's we were using them.
Our Prod-Sports MG Midget had one of their first thermatic fans fitted, that car held the under 1300cc lap records everywhere it raced an won the state hillclimb championship.
That same thermatic fan was removed when the car was sold and did sterling service in various road cars for about 30 years! The only thing that killed it was that it came off second best in an accident!