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A couple of things:  

Doubling up the horns and fan on the horn fuse could blow the fuse if both devices operate at the same time.  You could put in a bigger fuse, but the wiring feeding the fuse may not be big enough.  Since this should probably be a rare and transitory situation, it may never cause a problem.

The other thing is less obvious, and a bit of a long shot.  Some relays include a diode across the coil to quell an inductive spike when power is removed from he coil.  This in effect makes the coil polarity sensitive.  If your relay does have a diode, you've got the connections to 85 and 86 backwards.  Also, you've probably destroyed the diode. 

Other than that, the circuit looks OK.  I'd try another relay with 85 and 86 swapped.  If it still doesn't work, there's probably a wiring problem.

Some tests:

Make sure you have +12V on pin 30.  If you don't, check fuse and wiring.

Short 30 to 87.  This bypasses the relay, and the fan should run.  If it doesn't, suspect the relay, fan, or wiring to the fan.

Connect 86 to a good ground.  This should operate the relay and run the fan.  If it doesn't, suspect the relay.

Check the voltage at 86.  It should be close to 0 V if either the thermal switch or the override switch is closed, (or both).  Otherwise, it should read near +12 V.  If it doesn't, suspect the switches or wiring to them.

Good luck.

Ed

 

 

 

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4 hours ago, ed_h said:

A couple of things:  

Doubling up the horns and fan on the horn fuse could blow the fuse if both devices operate at the same time.  You could put in a bigger fuse, but the wiring feeding the fuse may not be big enough.  Since this should probably be a rare and transitory situation, it may never cause a problem.

The other thing is less obvious, and a bit of a long shot.  Some relays include a diode across the coil to quell an inductive spike when power is removed from he coil.  This in effect makes the coil polarity sensitive.  If your relay does have a diode, you've got the connections to 85 and 86 backwards.  Also, you've probably destroyed the diode. 

Other than that, the circuit looks OK.  I'd try another relay with 85 and 86 swapped.  If it still doesn't work, there's probably a wiring problem.

Some tests:

Make sure you have +12V on pin 30.  If you don't, check fuse and wiring.

Short 30 to 87.  This bypasses the relay, and the fan should run.  If it doesn't, suspect the relay, fan, or wiring to the fan.

Connect 86 to a good ground.  This should operate the relay and run the fan.  If it doesn't, suspect the relay.

Check the voltage at 86.  It should be close to 0 V if either the thermal switch or the override switch is closed, (or both).  Otherwise, it should read near +12 V.  If it doesn't, suspect the switches or wiring to them.

Good luck.

Ed

 

 

 

Thanks for this. Will try later, off to see TS2 at Gaydon in my 4A :D

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12 hours ago, ed_h said:

A couple of things:  

Doubling up the horns and fan on the horn fuse could blow the fuse if both devices operate at the same time.  You could put in a bigger fuse, but the wiring feeding the fuse may not be big enough.  Since this should probably be a rare and transitory situation, it may never cause a problem.

The other thing is less obvious, and a bit of a long shot.  Some relays include a diode across the coil to quell an inductive spike when power is removed from he coil.  This in effect makes the coil polarity sensitive.  If your relay does have a diode, you've got the connections to 85 and 86 backwards.  Also, you've probably destroyed the diode. 

Other than that, the circuit looks OK.  I'd try another relay with 85 and 86 swapped.  If it still doesn't work, there's probably a wiring problem.

Some tests:

Make sure you have +12V on pin 30.  If you don't, check fuse and wiring.

Short 30 to 87.  This bypasses the relay, and the fan should run.  If it doesn't, suspect the relay, fan, or wiring to the fan.

Connect 86 to a good ground.  This should operate the relay and run the fan.  If it doesn't, suspect the relay.

Check the voltage at 86.  It should be close to 0 V if either the thermal switch or the override switch is closed, (or both).  Otherwise, it should read near +12 V.  If it doesn't, suspect the switches or wiring to them.

Good luck.

Ed

 

 

 

Tried a different switch. 

green to pin 86

black to earth

fan comes on via this switch….

 

D92522B2-6CC9-4DFC-8910-6ACAD53B9AC0.jpeg

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26 minutes ago, RobH said:

image.thumb.png.90ba0fc142e7954b9cf7058fe22934a6.thumb.png.76f9c8c911bc77bc58db7f966aae2770.png

And that’s what I’ve removed today. I now just have wire going to 86, and another wire to earth. And, it’s working from the switch. :D
 

just need to get the sensor fitted and connected and hopefully all sorted. 
 

thanks all

John

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