1974 FJ40 horn issues and unknown connector on driver's side

[brasskey]

I am trying to diagnose the issue with my horns. They have never worked and I am just now getting around to looking at things. When I press any of the three horn buttons on the steering wheel, I can hear a click, but no horn sound. I have a new relay and put that in, but that didn't fix the issue. I also checked the fuse panel, but the fuse seems fine. I will note that the wiring diagram shows the HORN fuse in the second position from top, whereas my fuse cover is labeled as STOP in the same location (see photo). In searching on Mud, maybe I have a grounding issue? Just not sure what to look for before I purchase new horns if those happen to be the issue.

Also, does anyone sell new plastic connectors that the female wire spades to go into? Mine is obviously pretty brittle and degraded.

I also have an unknown connector on the driver's side close to the firewall (see last photos). Hard to tell because wiring is old, but the four wires seem to be 1) BLK w/ YEL stripe, 2). GRN w/ black strip, 3). BLU w/ red stripe, and 4). BLU w/ black stripe.

Looking at my diagram, there are no blue wires, so maybe those are faded and are the LP (light purple)? If so, still having a hard time tracking those four down on my diagram. Thought some of you all that are much more familiar might know right away what this connector relates to.
*EDIT: looking more into it, seems like that is "27 Computer - for USA"?

 

[Rocky_LC]

Do your horns honk if you just run a jumper direct to the battery?

That will tell you a lot.

It will check the horn, and the ground to it.

If you hear a click, that’s probably your horn relay. That seems to say your switch and the relay are working….

Rocky

 

[brasskey]

Do your horns honk if you just run a jumper direct to the battery?

That will tell you a lot.

It will check the horn, and the ground to it.

If you hear a click, that’s probably your horn relay. That seems to say your switch and the relay are working….

Rocky

Don't know why I didn't think of that. I will check that, thank you.

 

[brasskey]

Looks like the horns are good. Just checked both jumping to battery. So, if I hear clicking (which means solenoid is good), then maybe grounding issue on horns? Is there an area I should look for to help clean that up?

 

[TreadingLight]

If the horns went honk with + from the battery, then the horns are grounded.

You probably have a wiring issue (broken wire or connector) between the relay and the horns. I think it is a g/w wire.

You can buy 3-pin connector housings for 6.3mm terminals w/lance from Vintage Connections, Corsa Technic, and probably scamazon/fleabay.

Ex: 6.3mm Connectors - https://www.vintageconnections.com/products/6-3mm-connectors?variant=46131501171009

 

[brasskey]

If the horns went honk with + from the battery, then the horns are grounded.

You probably have a wiring issue (broken wire or connector) between the relay and the horns. I think it is a g/w wire.

You can buy 3-pin connector housings for 6.3mm terminals w/lance from Vintage Connections, Corsa Technic, and probably scamazon/fleabay.

Ex: 6.3mm Connectors - https://www.vintageconnections.com/products/6-3mm-connectors?variant=46131501171009

Thank you for the link on the connectors.

To clarify, I took the horns off and ran a jumper from male connector on horn to positive, and jumper from negative on battery to back of horn (up top close to horn bracket hole where it bolts down). When the horns are mounted, just positive from the battery doesn't work. So, maybe I need to clean up the back of the horn mount and where it is bolting to the car? Should it be clean metal on both sides? Where it is bolting to the car is painted metal. Should that be bare metal (see photos below).

 

[Pighead]

I have a new relay and put that in,

What kind of relay, OEM or the new-fangled black plastic box with 4 or 5 tabs?
Horn wiring is funny because the steering wheel buttons supply ground to the relay, not hot. It took me a minute to figger out how to do it.

 

[brasskey]

What kind of relay, OEM or the new-fangled black plastic box with 4 or 5 tabs?
Horn wiring is funny because the steering wheel buttons supply ground to the relay, not hot. It took me a minute to figger out how to do it.

OEM relay I assume as shown in first pictures. I did try an aftermarket one as shown in first post also. I think I'm getting ground to relay as I can hear it click when horn buttons are pressed. So, I'm thinking the horns themselves are not grounding well.

 

[TreadingLight]

Time to address all vehicle grounds. When I start on a 40, I make/add grounds from battery to frame, battery to engine, and engine or frame to firewall.

If your radiator/bib is real crusty you may need to run a ground to the horn mounts.

 

[charliemeyer007]

Since the horn beeps with jumper power to battery +, its ground is likely good - never hurts to clean/lube the mounting bolt and bracket surfaces. Separate ground wires to all lights and such isn't a bad plan.

Did you clean/lube the contacts inside the relay connector? That first pic show corrosion on the old relay contacts. Mount the relay after cleaning its mounting contact surfaces.

 

[brasskey]

Since the horn beeps with jumper power to battery +, its ground is likely good - never hurts to clean/lube the mounting bolt and bracket surfaces. Separate ground wires to all lights and such isn't a bad plan.

Did you clean/lube the contacts inside the relay connector? That first pic show corrosion on the old relay contacts. Mount the relay after cleaning its mounting contact surfaces.

I think I’ll just get new contacts and connecter to make everything fresh and go from there. I’ll also clean mounting bolt and surfaces on horns. Also check all negative connections from battery. Thanks for the help everyone.

 

[charliemeyer007]

So I use a q-tip to apply a thin layer of dielectric grease to the contacts on both sides of electrical connections to help repel corrosion formation.

 

[TreadingLight]

So, maybe I need to clean up the back of the horn mount and where it is bolting to the car?

Wouldn't hurt

Should it be clean metal on both sides?

On the side where your bolt head rests. The backside against the rad support doesn't matter.

Where it is bolting to the car is painted metal. Should that be bare metal (see photos below).

The mounting bolt should pick up the ground from the threads in the rad support. As long as there is no paint on the threads you are good.

But the question remains, is your radiator support well grounded through the chassis and back to the battery? Ancient ground cables and rusty hardware are the enemy here.

 

[brasskey]

Wouldn't hurt


On the side where your bolt head rests. The backside against the rad support doesn't matter.


The mounting bolt should pick up the ground from the threads in the rad support. As long as there is no paint on the threads you are good.

But the question remains, is your radiator support well grounded through the chassis and back to the battery? Ancient ground cables and rusty hardware are the enemy here.

I will check all that. Thank you.

 

[charliemeyer007]

A while back I bought new battery cables 2/0 size. I ran the red to the starter and the black to a bolt on the engine. I took my old 2 black cable and ran it from that same ground engine bolt down the frame ground under the brake tee fitting. I ran a #10 black wire from that frame ground up to ground the cowl. At least 1/3 of my exterior lights have a separate ground wire

 

[brasskey]

Wouldn't hurt


On the side where your bolt head rests. The backside against the rad support doesn't matter.


The mounting bolt should pick up the ground from the threads in the rad support. As long as there is no paint on the threads you are good.

But the question remains, is your radiator support well grounded through the chassis and back to the battery? Ancient ground cables and rusty hardware are the enemy here.

It does seem grounding on radiator support is the issue. I ran a negative jumper from horn to battery and horns work (first two images). So, need to figure out why radiator support isn't grounded well. I could obviously just run a more permanent, cleaner negative connection to replace jumper if I can't figure out grounding issue with radiator mount.

Is there supposed to be a dedicated ground from support back to battery? Or, just the two mounting bolts back to chassis (see second two photos). Obviously, the mounts for the radiator support have quite a bit of surface rust. Maybe clean those up? They do seem to have some paint on the bottom of threads. The last photo is the negative ground to the chassis going to battery.

 

[TreadingLight]

It's normally grounded through the chassis or front bib. Just via the nuts and bolts that hold it all together.

Nothing wrong with running a ground wire. The alternative would be to disassemble, clean, and reassemble the front bib and rad support. The bolts are probably quite rusty.

 

[TreadingLight]

II guess I'll just reiterate the note above about having good ground wires in general. It is possible that you have poor body/chassis grounds in general, and that repairing those would sort you out.

If you don't feel like tackling the factory ground cables, or have already done so and still have issues, then address the grounding to the rad support itself with a dedicated ground or by cleaning/replacing the nuts n bolts.

 

[brasskey]

II guess I'll just reiterate the note above about having good ground wires in general. It is possible that you have poor body/chassis grounds in general, and that repairing those would sort you out.

If you don't feel like tackling the factory ground cables, or have already done so and still have issues, then address the grounding to the rad support itself with a dedicated ground or by cleaning/replacing the nuts n bolts.

Thank you for all the help and suggestions! I’ll report back.

 

[brasskey]

Replaced all grounding cables (engine and frame), positive cable to starter, and battery terminals with @Fourrunner's kit. Very heavy duty and nice. Unfortunately, still not getting horns. Don't really feel like taking apart the radiator and radiator support, so will just live with it for now until I can find more time. For now, just ran a ground wire from horn to battery like I tested above and horns work. Thanks again for everyone's help.