19 replies to this topic

[minisilverbullet]

Started wiring this up today before it got dark ( blooming daylight saving). I suspect I have an earth issue.

So I took the permanent feed from the solenoid, added a 25a inline fuse the to pin 30 on the relay.

Added a switch, took a switched feed from the radio, added a 3amp inline fuse then into the switch. Ran the wire from the switch to pin 86. Added a earth, as the switch is illuminated.

The windscreen it'self has 3 wires, I took the centre wire to earth. And then ran the outer 2 to pin 87 on the relay.

Pin 85 Is earthed

With this set up the relay buzzes! If I remove the windscreen earth it stops. I have tried earthing the outside wires of thevwindscreen and using the centre wire to the relay, it still buzzes.

I assume I have made a mistake with the earth, but what am I doing wrong ?

Additional info- when I remove the windscreen earth, the relay clicks and functions as normal ( no buzzing)

[Dan]

What terminal did you come from at the solenoid? What rating is the relay? What size is the wire you've used? Are you combining both screen elements together?

[minisilverbullet]

Relay and wire is rated at 30amps

I took the permanent feed from the solenoid, same place as my spots. Hard to describe, but I added a ring terminal there,

I have added both screen elements together yes.

[Dan]

I think you might be overloading the relay and wiring. I seem to remember these screens are 17A per side for a total of 34A if you link them, and that's theoretical at 12v so with the engine running it'll be closer to 40. See what happens if you just connect one element to it. Bear in mind the relay may be physically damaged now and do inspect the wiring thoroughly for heat damage.

[Curley]

I assume you're talking about a 'monte carlo' front screen? I seam to remember these are dual zone. The center wire is the earth and the two side wires for driver and passanger. I could be wrong but try disconnecting one and try again.

[minisilverbullet]

I assume you're talking about a 'monte carlo' front screen? I seam to remember these are dual zone. The center wire is the earth and the two side wires for driver and passanger. I could be wrong but try disconnecting one and try again.

Yip it is a monte screen, as above I connected the centre to earth and the two outer wires to the relay.

[minisilverbullet]

I think you might be overloading the relay and wiring. I seem to remember these screens are 17A per side for a total of 34A if you link them, and that's theoretical at 12v so with the engine running it'll be closer to 40. See what happens if you just connect one element to it. Bear in mind the relay may be physically damaged now and do inspect the wiring thoroughly for heat damage.

Thanks for the reply. That would be an inconvenience, maybe I should try a higher amp relay and wiring.

[GraemeC]

Try half the screen first. If that works you can either replace what you have with higher rated stuff or duplicate it so each side is individually relayed and fused (one switch can operate both relays).

[mk1leg]

well My monte style heated screen only has 2 wires and 1 was feed and the other is earth..................wired up through a relay and works fine clears the screen within 3 mins of switching on.............

earth wire

relay on inner driver wing behind stiffner

[minisilverbullet]

So the mystery deepens ( at least for me)

So with the far left wire connected to pin 87 on the relay there is 12v from both the centre of the screen and the far right wire.

If I earth the centre wire the relay buzzes if I earth the far right wire no buzzing.

With the centre wire of the windscreen connected to the relay, there is 12v from both the right and the left sides of the screen. If I earth either wire the relay buzzes

With the right side wire on the relay, there is 12v at both the centre and the left wire. The centre wire when earthed makes the relay buzz. The left hand wire when earthed does not buzz the relay

[phil hill]

I think you need to draw out the circuit for us to understand, I can't quite get a picture of it in my head.

 

As a variation on a theme instead of feeding each side and grounding it in the centre, how about feeding the centre and grounding each side ??

 

Phil.

[minisilverbullet]

Diagrams of the 3 wiring scenarios. 

 

 

 

 

[Dan]

Wiring it completely across the screen in one you are putting the two elements in series.

[minisilverbullet]

I now understand that I will need to wire each half of the screen separately, each with its own relay.

But....what I don't understand, is how this will work. If I where to follow wiring "a" above just to wire up the left side of the screen. If i run the supply to the left wire on the screen and then Earth the middle wire, the relay buzzes.

[Dan]

It's probably been damaged by overloading. It should be well within spec running just one element, try a new one and see if it works.