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Any Auto Electrician Here?

subie

By subie,
in General Maintenance

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GeeTR Grand Master

GeeTR

Posted
Posted (edited)

Horn relays? I'm getting de ja vu :D

Im no auto-elec, but fuses pop when they pass their current limit for an amount of time. If your popping 15amp ones instantly (and there should 10's in there) Then theres a pretty strong short circuit somewhere.

I suggest the power wire for the horn, is touching the chassis somewhere. Tracing can be very tedious. At the relay, see if there continuity between the power (that goes to the horn) and the chassis. If there is, its def a short circuit.

Good luck, i hate finding shorts through harness wiring :P

Edited by GeeTR
blind_elk Grand Master

blind_elk

Posted
Posted

But it seems it's not until subie presses the button that the short occurs to blow the fuse.

Might I suggest that the action of pressing the horn is enough to depress the live contact on the button so that it makes contact with the steering column, causing the short.

Make sure the live contact onto the button is fully covered (insulated).

Jmaac Proficient

Jmaac

Posted
Posted

Depends on the state of the circuit, either naturally open or closed. As above you'll have to trace back the wires and look for any potential problems.

Check the connections at the s/wheel, fusebox (inc. relay) and at the horn itself. Is it the stock oem s/wheel?

GeeTR Grand Master

GeeTR

Posted
Posted (edited)
But it seems it's not until subie presses the button that the short occurs to blow the fuse.

Yah, even with a dead fuse, wouldnt the relay still click shut? (assuming the s.wheel switch trigger is good to go) Replacing fuse and hitting the button causes the power to to the chassis throguh a short circuit, killing the fuse?

I would think a quick test would be to test the power pin at the relay end with the multimeter set to continuity, or resistence. If touching the pin and the chassis proves a result..then uv got a S/C

Im just thinking out aloud here, could be wrong :(

Edited by GeeTR
QWK32 Veteran

QWK32

Posted
Posted (edited)
Yah, even with a dead fuse, wouldnt the relay still click shut? (assuming the s.wheel switch trigger is good to go) Replacing fuse and hitting the button causes the power to to the chassis throguh a short circuit, killing the fuse?

I would think a quick test would be to test the power pin at the relay end with the multimeter set to continuity, or resistence. If touching the pin and the chassis proves a result..then uv got a S/C

Im just thinking out aloud here, could be wrong :(

Yeah thats right. most horn buttons switch a ground signal or -ve signal to a relay, which then switches the +ve feed to the horn, it gets its -ve side from the chassis. its the +12v feed to the horn that is the line with a fuse in it.

and yes the best way to check if its a short on in the wire to the horn is to, disconnect the horn, and do a continuity test between the +ve feed to the horn (on a relay usually pin 87 on a bosch relay), and a chassis ground. if you get continuity its the wiring to the horn which will be mainly in th engine bay.

edit: just went and checked the relay and the horn relay pin to test is pin number 3, nissan number thiers differently.

Edited by QWK32

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