Sunbaked '76 Cali 280z

[Rob Gaskin]

I don't understand what you're saying Rob? I am trying to test the horn end

Ok but I was reading about you understanding the steering wheel end.

Have you done a simple test of connecting 12volts across the horn? I'd take the horn off the car to do that so that you can eliminate a poor earth/ground connection. If it sounds and you get the relay to click (as you stated earlier) then it should be a fairly straightforward task of tracing the wiring back from the horn to the relay to find any break.

 

[Faster Behr]

Perhaps he meant beep

 

[toopy]

Ah ok, that makes sense. I can only see the one wire going to it. So with the power probe, should the horn work if I send a positive (or negative?) charge directly to the horn's body with a power probe?

Positive feed to the spade terminal, if still doesn't sound, try attaching the small earth lead to the body of the horn and re-test.

 

[Robotsan]

Ok but I was reading about you understanding the steering wheel end.

Have you done a simple test of connecting 12volts across the horn? I'd take the horn off the car to do that so that you can eliminate a poor earth/ground connection. If it sounds and you get the relay to click (as you stated earlier) then it should be a fairly straightforward task of tracing the wiring back from the horn to the relay to find any break.

Yes - that's what I said I was trying to do in the message before yours: https://zclub.net/community/index.php?threads/sunbaked-76-cali-280z.29585/post-348131 - but I'm not sure how!

Will try again with the horn off the car. Thanks!

 

[Robotsan]

Positive feed to the spade terminal, if still doesn't sound, try attaching the small earth lead to the body of the horn and re-test.

Hmm thought so. That definitely didn't work last night. But you mean try attaching the little crocodile clip that comes off the power probe to the horn too? Will try that later. Thanks.

 

[MCBladeRun]

Not to throw you off with other things to consider, did the horn ever work?

 

[Robotsan]

Not to throw you off with other things to consider, did the horn ever work?

Haha, nope, not in my ownership. But until now I assumed that was because the little plastic piece that held the contact against the wheel hub was broken. Turns out there's more to it! I'm not thinking this has anything to do with the recent work I've done with the switches/stalks, in case that's what you're thinking.

 

[MCBladeRun]

Haha, nope, not in my ownership. But until now I assumed that was because the little plastic piece that held the contact against the wheel hub was broken. Turns out there's more to it! I'm not thinking this has anything to do with the recent work I've done with the switches/stalks, in case that's what you're thinking.

Well, if you've got that tester with the lamp, why not get someone to honk the horn whilst you hold it on the horn circuit? If it lights up, your 2x horns need replacing

 

[Robotsan]

Well, if you've got that tester with the lamp, why not get someone to honk the horn whilst you hold it on the horn circuit? If it lights up, your 2x horns need replacing

Ah ok, sounds like a plan. Which part of the circuit?

I've tested the horn wire for continuity from the headlights stalk to the main harness and that was fine.. and the horn fuse is ok .. but then after that I can't see the horn circuit again until the wire actually connects to the horn itself.

 

[Robotsan]

I just tested the horn on and off the car with 12v via the power probe. Tried it on the horn connector and the body of it, and with the earth lead attached and not. Nada. Does that prove the horns themselves are defunct then?

 

[MCBladeRun]

I just tested the horn on and off the car with 12v via the power probe. Tried it on the horn connector and the body of it, and with the earth lead attached and not. Nada. Does that prove the horns themselves are defunct then?

Lol

You're short circuiting the earth there pal.

Attach the croco clip to the end of that black wire, and then do that again with the earth casing

Just editing my reply here George: there's 2x logical things we need for that horn to work.

Firstly with the horn off of the car like it is, we need to establish that it works, by that YouTube video, it looks like you're putting both probes to the metal casing, causing a short circuit as I said above.

Being a circuit, your principles for it to work, should be 12v positive (your red croco clip) to attach to that black wire (12v input) then your black croco clip, needs to be on the earthed metal casing. This should create a circuit making the horn sound. It shouldn't work backwards however, as that would suggest you've got a +ve chassis and not a standard -ve or earthed chassis (ridiculous as it sounds).

If that horn doesn't make a noise then, there's the problem. You could take it apart as Datsun were clever with be able to tune them slightly I believe?

The 2nd logical thing is that the wire that goes to the horn, from the horn pad. Is that wire working at the horn end? Put your light up probe between the wire and your earthed chassis. Have a helper press the horn pad, it should light up. If not, there's your problem.

Remember, you could have 2x issues here. Horn and horn pad.

I've been drinking and have too much free time this evening.. sorry for wall of text

 

[Robotsan]

Lol

You're short circuiting the earth there pal.

Attach the croco clip to the end of that black wire, and then do that again with the earth casing

Just editing my reply here George: there's 2x logical things we need for that horn to work.

Firstly with the horn off of the car like it is, we need to establish that it works, by that YouTube video, it looks like you're putting both probes to the metal casing, causing a short circuit as I said above.

Being a circuit, your principles for it to work, should be 12v positive (your red croco clip) to attach to that black wire (12v input) then your black croco clip, needs to be on the earthed metal casing. This should create a circuit making the horn sound. It shouldn't work backwards however, as that would suggest you've got a +ve chassis and not a standard -ve or earthed chassis (ridiculous as it sounds).

If that horn doesn't make a noise then, there's the problem. You could take it apart as Datsun were clever with be able to tune them slightly I believe?

The 2nd logical thing is that the wire that goes to the horn, from the horn pad. Is that wire working at the horn end? Put your light up probe between the wire and your earthed chassis. Have a helper press the horn pad, it should light up. If not, there's your problem.

Remember, you could have 2x issues here. Horn and horn pad.

I've been drinking and have too much free time this evening.. sorry for wall of text

Haha, yep as you can tell, I don't know what I'm doing! And don't worry - I welcome drunk electrical advice, bring it on!

Ok.. when you say black wire.. what black wire? The only black wire in the video is the one that the little crocodile clip from the power probe is on?

Just to clarify how I had that test set up.. following the instructions that came with the power probe, I had the red main crocodile clip on the positive battery terminal, and the black main one on the negative. There's then a small separate black wire with a mini crocodile clip coming off the probe which is the earth right? That was attached to the horn, as per @toopy's suggestion earlier.
Is that not the right way to do it then?

The wire test with the test light makes sense.. so the test light's crocodile clip connected to the chassis to earth it, then the tip of it on the end of the wire, then press the horn?

 

[MCBladeRun]

Haha, yep as you can tell, I don't know what I'm doing! And don't worry - I welcome drunk electrical advice, bring it on!

Ok.. when you say black wire.. what black wire? The only black wire in the video is the one that the little crocodile clip from the power probe is on?

Just to clarify how I had that test set up.. following the instructions that came with the power probe, I had the red main crocodile clip on the positive battery terminal, and the black main one on the negative. There's then a small separate black wire coming off the probe which is the earth right? That was attached to the horn, as per @toopy's suggestion earlier.
Is that not the right way to do it then?

The wire test with the test light makes sense.. so the test light's crocodile clip connected to the chassis to earth it, then the tip of it on the end of the wire, then press the horn?

Bare with Gents, might be committing professional suicide here...



Right... Battery on the right, it's a black box with a red and black terminal representing our battery in the car with +ve and -ve terminals.

On the left, is a well drawn horn or, sounder. It's not to scale either. It's blue outer casing is made of metal, and it's the negative terminal of the circuit the wires are attached to. When it is installed in the car, you don't see any wires because, the metal casing is attached to the chassis, and the negative terminal of the battery is also attached to the very same chassis. (This is omitted for clarity of the drawing).

The orange wire represents either the fly lead that attaches the positive end from the horn pad, to the horn, or it's possibly a metal-tab like terminal, that is sticking out of the horn, covered in plastic (so it doesn't short against our blue metal horn case).



Ok, so here is the drawing again, with the flow of current, represented here, by yellow arrows. This flow of current, then drives energy, through our red arrows from the battery, via the orange wire, or tab from the horn. This then goes through an electro-magnet and then back out via the blue metal earth along our -ve earth path (black arrow) and back to the battery via the -ve earth terminal.

HONK!

 

[MCBladeRun]

The wire test with the test light makes sense.. so the test light's crocodile clip connected to the chassis to earth it, then the tip of it on the end of the wire, then press the horn?

This is correct for testing the horn circuit of the car, be careful not to put the horn wire to the chassis whilst horn pad is pressed - it will short and blow your fuse

 

[Robotsan]

Bare with Gents, might be committing professional suicide here...

View attachment 56555

Right... Battery on the right, it's a black box with a red and black terminal representing our battery in the car with +ve and -ve terminals.

On the left, is a well drawn horn or, sounder. It's not to scale either. It's blue outer casing is made of metal, and it's the negative terminal of the circuit the wires are attached to. When it is installed in the car, you don't see any wires because, the metal casing is attached to the chassis, and the negative terminal of the battery is also attached to the very same chassis. (This is omitted for clarity of the drawing).

The orange wire represents either the fly lead that attaches the positive end from the horn pad, to the horn, or it's possibly a metal-tab like terminal, that is sticking out of the horn, covered in plastic (so it doesn't short against our blue metal horn case).

View attachment 56560

Ok, so here is the drawing again, with the flow of current, represented here, by yellow arrows. This flow of current, then drives energy, through our red arrows from the battery, via the orange wire, or tab from the horn. This then goes through an electro-magnet and then back out via the blue metal earth along our -ve earth path (black arrow) and back to the battery via the -ve earth terminal.

HONK!

That is a brilliant bit of work, thank you sir
HONK indeed!

I now understand the workings of the circuit thanks to your very scientific diagram. But I still don't understand your original instructions about the power probe.. or more specifically, how I'm meant to use the power probe. Sorry. Maybe best if I drop you a DM another day instead, to spare everyone else the tedium of watching me trying to learn basic electronics.

 

[Robotsan]

Just to clarify, this is the kind of power probe that's powered by the battery.. if that makes a difference? As I know there's some that are self-powered.

 

[toopy]

Just to clarify how I had that test set up.. following the instructions that came with the power probe, I had the red main crocodile clip on the positive battery terminal, and the black main one on the negative. There's then a small separate black wire with a mini crocodile clip coming off the probe which is the earth right? That was attached to the horn, as per @toopy's suggestion earlier.
Is that not the right way to do it then?

That is correct but you then hold the probe end against the positive terminal on the horn (metal tab) and then press the button (rocker switch) on the probe that sends a positive feed through the probe end. This basically copies what happens when the horn pad is pressed.

 

[Robotsan]

That is correct but you then hold the probe end against the positive terminal on the horn (metal tab) and then press the button (rocker switch) on the probe that sends a positive feed through the probe end. This basically copies what happens when the horn pad is pressed.

Cheers Toopy. Good, that's exactly what I did, but there was nada. Guess the horns are fubared then. I'll be testing the wiring properly tonight so that should confirm it.

 

[Rob Gaskin]

Cheers Toopy. Good, that's exactly what I did, but there was nada. Guess the horns are fubared then. I'll be testing the wiring properly tonight so that should confirm it.

Guys will a probe pass enough current for a horn?

 

[toopy]

Guys will a probe pass enough current for a horn?

A Sealey one i was looking at has an 8 amp overload cutout, can't imagine a horn is going to pull any more than 2 amps max