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Engine Cooling Fan Override Switch - Using an A/C Switch

Maiku

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1991 VN Executive S2
After reading immortality's guide here, I thought this could be done with an A/C switch where the light could be used for an indicator for if the fan is running or not, and the switch could be used to manually start the fan. The way I have done this, the light will show the fan to be running if the fan is started manually by the switch, or automatically by the ECU. Now that it is all working, I am thinking of changing the globe in the switch to a couple LEDs to give it better visibility.

Note: I did this to a Series 2 VN, so I think it should work for VN-VP and maybe VR-VS, but I would double check wiring before doing something similar on other models.


Some of the Parts and tools I used I had already, some I bought for the mod.

Parts I used :
  • 5m of blue wire (Super Cheap Auto) ~$4
  • 5m of brown wire (Super Cheap Auto) ~$4
  • 3m of black wire (Super Cheap Auto)
  • Packet of 15 Quick TAB Joiners, used 2 (Dick Smiths) $4.96
  • A/C switch from a VN/VP (U-Pull-It) ~$1
  • Wire Connector (Dick Smiths)

Tools I used :
  • Flat Head Screwdriver
  • Digital Multimeter (Dick Smiths) $16.99
  • Bent coathanger


1. Since my Engine Cooling Fan's plug was a little loose so I first pulled it apart to clean it, to make a better connection (pic).

2. Once cleaned, I reattached the wires from the car's loom, and included 2 new wires (pic). These would be for the indicator light to indicate if the fan is running or not.

3. The plug was then reassembled (pic).

4. I ran those 2 new wires to the Fuse/Relay box under the hood. I attached the wires to a connector, and attached the connector to the Fuse/Relay box with cable ties (pic).

5. I then Attached 2 new wires to the connector (pic). Since I couldn't find an easy way through the firewall, I decided to run the wires back to the driver's side lights, and behind the front quarter panel. I fed the wire through there, with the bent coathanger, and into the cabin via the rubber stopper used to run wires between the cabin and the doors.

6. Then I attached the 2 earthing wires to manually switch on the fan. To connect them to existing wiring, I used some "Quick TAB Joiners" I got from Dick Smiths. One wire connected to the blue wire with white tracer wire coming from the ECU (pic) and the other to the earth of the cigarette lighter (pic). I probably didn't need to use thick wire for this part, but it was all I had on hand at the time. I would say I could have used thinner wire and would have worked as well.

7. Then I attached the 2 wires from the engine bay and the 2 earthing wires from inside the cabin to the plug for the back of the switch (pic).

8. All that was left to do was to mount the switch, and plug in the wires. The light is off when the fan is not running (pic) and lights up when it is (pic).

9. I didn't know what to do about the button since I didn't want 2 A/C buttons on my dash. I started by taking off the A/C sticker off the button, and it looked alight like that (pic).


A couple steps I excluded from above since they were just using the multimeter to make sure wires were connecting properly, check the voltage of the fan, and work out the pins on the switch.

This is just to show how I did it, but could be done better other ways. For example, the wired from the fan to the light in the switch could be got from the base of the relay, and done in one length of wire, and it would work just as well.

Note: Not that it might matter, but I tested the voltage coming from the fan, and it looked to be getting 14V not 12V. From what I have seen, the globe had no problems with this.


I included some pics that might help with doing a similar mod:

Gregory's Service and Repair Manual style Schematic.
This is more for my reference, but it gives a clearer look at how the mod is done.

A/C Switch Pinout
 

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