My aux fan froze up on my 82 xjs he, so I installed new twin elec fans from faster jags, also a new alum radiator while I was at it. I decided to use the old aux fan circuit to control my new fans using a separate 40 amp relay. All is working well except the fans are running all the time my heater or ac is turned on, I think this is normal from what I have read here but i would like them to run only when the temp switch calls for it in the winter. can someone tell me what wire to unplug from the diode pack to get the results I want if possible. Thanks in advance.

 

I'm working off a later wiring schematic but I think pulling either of the green/brown wires will do the trick

Cheers
DD

 

There is a wire that goes from the aircon compressor to the fan. When the heater is on (ie in any position except off) this wire is live and activates the (OEM) auxiliary fan.

Great idea to have one fan running when the aircon is called for, IMO. So I think the solution is to separate the two fans. One always on when the heater is on (remember the aircon is always on if the heater is on) and the second wired up to come on with the OEM temp switch in the water pump inlet casting.

This is the Grant Francis solution (genuflects towards Southern Cross), that he advised me about and I use it and it is great. He has the explanation of the wiring changes required, not hard to do, and I am sure he will help you. Of course you could wire both up to come on in this way, but, for me, safety advises one always on with the aircon.

Greg

 

Thanks Doug that did the trick.

 

When my diode pack recently went out I just straight wired my fan. While it is technically wasteful so is a mechanical fan.

Here was my logic.

If the car is cold the stats aren't letting coolant through the radiator anyway so what harm does it do?? If its cold out and the fans "over-cool" then the thermostats will just do their jobs and balance between the two and you will be fine.

If the issue is you don't want to waste electricity and the lifespan of the fans I guess I understand but it just seems unnecessarily complicated to me...