Horn relay issues

[ThomasMoore]

Hey there,

 

 

Can anyone help a newbie with what is probably a really simple question? I replaced the horn on my truck (the old stock one had died a long time ago, somehow managed to get it through the roadworthy minus a horn), wired it in place, worked like a charm and then died in the ass. From what I can tell the horn relay died. Went looking for another relay (the old one is a 3 pin 12V 15A that looks something like below):

 

 

 

Apparently the only three pin relays are for indicators (i.e. they flash), and no-one has heard of a three pin relay for a horn. I got hold of a stock lighting/horn relay (four pin, 12V 30A) which looks something like this:

 

 

Question is, how do I wire this together? I thought it would be pretty simple, i.e. wiring (1) - (85), (3) - (30), (2) - (86/87). I connected 86 and 87 together before putting pin (2) on (86). Sorry if this is a really basic question, but it's been bugging me all weekend as it should be really, really simple. Happy to provide photographs if need be (yes, it definitely is the horn relay), and it worked fine before the relay blew out. Any suggestions would be really appreciated.

 

 

Thomas

[RowdoggNZ]

Screw it dude, get an airhorn.

 

 

I did

[ThomasMoore]

Screw it dude, get an airhorn.

I did

 

Heh, would love to and will do, but over here they are considered "novelty" and aren't allowed as primary horns.

 

Anyone?

[RedPath88]

One would think that it should just be a sinply hook up... where is the relay located in the truck? If I can I'll take a look at mine to get a better understanding of it.

 

 

Have you considered a replacement relay from nissan... or one from a wrecking yard?

[Alkorahil]

The stock horn relay is 3 pin............I looked it up in the computer and took a look for you

 

part# 25630-79960

 

 

 

 

I am not sure what you got....

Edited June 16, 2008 by Alkorahil

[mws]

The horn is a GROUND switched circuit, which is causing the confusion. Most circuits in a car are hot switched. No worries, just need to wire it up a bit different.

 

On the NEW relay:

 

Pins 30 and 85 need to be connected to a 12V source. Can be hot all the time, or a switched source, depending on whether you want your horn to be be usable when key is off. Stock config would have it hot all the time.

 

Pin 87 goes to the + input of the horns

 

Pin 86 goes to stock horn switch in the steering column.

 

Which is the effectively the same as what you described, but reversed. So how you hooked it up WILL work equally well.

Is it not working?

If so, then I would suspect the contacts in the steering column. The pin that wipes on the copper ring does wear down over time.

[ThomasMoore]

The horn is a GROUND switched circuit, which is causing the confusion. Most circuits in a car are hot switched. No worries, just need to wire it up a bit different.

 

On the NEW relay:

 

Pins 30 and 85 need to be connected to a 12V source. Can be hot all the time, or a switched source, depending on whether you want your horn to be be usable when key is off. Stock config would have it hot all the time.

 

Pin 87 goes to the + input of the horns

 

Pin 86 goes to stock horn switch in the steering column.

 

Which is the effectively the same as what you described, but reversed. So how you hooked it up WILL work equally well.

Is it not working?

If so, then I would suspect the contacts in the steering column. The pin that wipes on the copper ring does wear down over time.

 

Thanks for the reply - very much appreciated. I've just spent the last hour trying varying configurations, but still no joy - at least when it's hot wired I can get some sound out of it before it dies 10 seconds later. The first problem seems to be that the +ve input on the old 3 pin relay is burnt out, so I wired a new +ve direct from the battery to pins 30 & 85. This still doesn't resolve any issues:

 

Following your instructions, it should look like this, right?

 

 

I'll double check the contacts in the steering column, but i'm doubtful that this is the issue. How would I check the contacts in the steering column? I'm assuming the button here is hot?

 

 

Thomas

[RowdoggNZ]

Heh, would love to and will do, but over here they are considered "novelty" and aren't allowed as primary horns.

 

Anyone?

 

Oh really? Thats kinda suck, not even single blast air horns? Good luck anyway and sorry i can't help further.

[mws]

Thanks for the reply - very much appreciated. I've just spent the last hour trying varying configurations, but still no joy - at least when it's hot wired I can get some sound out of it before it dies 10 seconds later. The first problem seems to be that the +ve input on the old 3 pin relay is burnt out, so I wired a new +ve direct from the battery to pins 30 & 85. This still doesn't resolve any issues:

 

Following your instructions, it should look like this, right?

 

 

I'll double check the contacts in the steering column, but i'm doubtful that this is the issue. How would I check the contacts in the steering column? I'm assuming the button here is hot?

Thomas

 

Yes, that schematic appears correct.

 

The spring loaded copper wiping contact in the steering column should show 12 V. When this is connected to a ground (any ground), the relay will be energized and sound. But if the path to ground is compromised, no horn. Potential faults include:

- copper wiping contact worn down

- Spring broken or weak (not pushing firmly against ring)

- Wiping surface ring on back of steering wheel corroded or worn through

- broken wire within wheel

- dirty/broken contacts on horn switch

- bad ground path from steering wheel to column to chassis

 

Good luck!

[mws]

Note: I just modified the plunger/wiping contact in my pathy with 240K miles. The tip had worn down until it was completely flat. That resulted in the corners being sharp, and they scraped away the surface of the ring until it cut all the way through.

Had to replace the ring, and I carefully filed and sanded the corners of the plunger to a nice smooth radius.