4.0l XJ overheating? Start here - the basics!

[werd]

Before I start this project could you answer two questions please?
#1 You have said if you're running the AC, the fans they will change to high automatically. Does that mean they run at low speed as well?
#2 When the fans cut in at 106°, isn't that a bit late to start cooling? With the stock setup the belt fan is already trying to cool the system down before the electric fan cuts in.

[junglejuice]

Before I start this project could you answer two questions please?
#1 You have said if you're running the AC, the fans they will change to high automatically. Does that mean they run at low speed as well?
#2 When the fans cut in at 106°, isn't that a bit late to start cooling? With the stock setup the belt fan is already trying to cool the system down before the electric fan cuts in.

Ok, the way it works is like this, in auto the fans both run in low speed mode so you're getting airflow across the entire radiator just at a lower speed, once the AC or the temp rises to the point that the aux fan would normally turn on the fans both change from low to high speed.

When in manual mode the fans both run at full or high speed irrespective of the temp or the AC status.

If you use the trans temp or 4wd input the result is the same as manual.

Does this help clear things up for you?

[werd]

Sure does, thanks. I don't think I've ever seen the electric fan move until it hit 106.

[Billnick]

You may notice it wont get as hot with the aux fan running low speed on the hot side of the radiator. As you remember from school, the hotter the coolant is the faster it will lose its heat.

[werd]

You may notice it wont get as hot with the aux fan running low speed on the hot side of the radiator. As you remember from school, the hotter the coolant is the faster it will lose its heat.

I must have wagged school that day

[werd]

Well, I finished my fan install today. After a lot of reading through the workshop manual I came up with the circuit below.

On the left the relay with the flashing LED is optional. I installed it so I wouldn't forget to turn the fan back on. Because I used a 12 volt supply that is always on it also doubles as an anti-theft deterrent.

With the switch, up is auto, centre is off and down is on.

To wire in the relay, find the dark blue with a pink stripe, cut it and put you relay here. Connect the dark blue/pink wire closest to the existing relay to the new relay. The other connection on the new relay, run the wire into the switch on the dash and back to the dark blue/pink wire that runs to the PCM as per diagram.

[Richard buttocks]

The relay you added to run the new fan shouldn't be in series with the original relay
Depending on what relay you use, the voltage it receives to switch on may not be enough.

Hope that makes sense

P.s. its not -12v either
Its 0v....

[werd]

The relay you added to run the new fan shouldn't be in series with the original relay
Depending on what relay you use, the voltage it receives to switch on may not be enough.

Hope that makes sense

P.s. its not -12v either
Its 0v....

Okay, I'll fix it. Thanks for that.