Defender thermo override switch

**MinniTheMoocha** · 5th January 2011, 04:03 AM

Has anyone got details of an override switch for the thermo on a Defender.

I was going to supply 12v via a separate switch but am not sure if this could interfere with the A/C. It switches on a/c pump clutch

Was thinking of some arrangement where if you use the override switch a relay disconnects the A/C supplied power.

A circuit diagram would be great.

Thanks
MtM

**Michael2** · 5th January 2011, 05:50 AM

6 PIN Relay

PIN 1 PIN 2 PIN 3
PIN 4 PIN 5 PIN 6

+'ve to PIN 1 and Earth to PIN 6, fit a switch to this circuit in the dash (switch either +'ve or -'ve.)

When power is applied PIN 2 & PIN 3 are in common

When no power is applied PIN 4 & PIN 5 are in common

Cut into your A/C power supply and put PIN 4 & PIN 5 in line. Then the A/C will operate the fan and work normally, till you switch this relay on.

Connect power to a thermostat switch and then run it to the fan via PIN 2 & PIN 3 (into 2, out of 3). Then when you switch the relay ON (power to PIN 1), the fan will be activated by the Thermo switch, and the A/C power supply will be disrupted. Obviously you won't have A/C in this override mode.

My inclination would be to just turn the A/C on if it's getting too hot for the motor. That way we could both (the engine & I) enjoy some extra cooling.

**PhilipA** · 5th January 2011, 08:09 AM

I found an easier way to stop the aircon turning on with less complexity was to fit a diode in the line from the aircon switch to the fans.
Available at Jaycar.
Regards Philip A

**MinniTheMoocha** · 5th January 2011, 09:39 AM

Originally Posted by PhilipA

I found an easier way to stop the aircon turning on with less complexity was to fit a diode in the line from the aircon switch to the fans.
Available at Jaycar.
Regards Philip A

Is there a special diode that needs to be used? ie. able to handle the current for running the thermo fan.

**PhilipA** · 5th January 2011, 11:38 AM

I got a big one . I just had a look for one but couldn't find it.

I had a look in the Jaycar catalogue and this appears to be it.
http://www.jaycar.com.au/products_uploaded/ZR-1054.pdf

Now it was almost 20 years ago, but I recall (maybe ) that the interior fans on the aircon were on a separate circuit to the clutch and all I had to do was isolate the clutch.
So I used the diode in the sensor wire of the relay that I fitted for the fans which ran from the clutch. I just added another sensor wire from a switch, then no back current energised the clutch when I manually turned on the fans.
Regards Philip A

**MinniTheMoocha** · 5th January 2011, 04:48 PM

Originally Posted by PhilipA

I got a big one . I just had a look for one but couldn't find it.

I had a look in the Jaycar catalogue and this appears to be it.
http://www.jaycar.com.au/products_uploaded/ZR-1054.pdf

Now it was almost 20 years ago, but I recall (maybe ) that the interior fans on the aircon were on a separate circuit to the clutch and all I had to do was isolate the clutch.
So I used the diode in the sensor wire of the relay that I fitted for the fans which ran from the clutch. I just added another sensor wire from a switch, then no back current energised the clutch when I manually turned on the fans.
Regards Philip A

I have purchased a bunch of these from Jaycar and will combine them together to get the required amperage.

Altronics had a 25amp diode that could have been used but I had already bought the ones from Jaycar.

This makes for a simple modification without requiring a complicated relay setup.

Thanks
MtM

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