1969 e200 v8 Econoline.

I'm battling a horn issue that is about to make me take the steering wheel off to hunt for a short but something doesn't add up.

I can get the horn to blow with a direct short from the battery. And I can short across terminal 1 and 2 of the relay plug to get the horn to work. But now two relays don't work. I've checked the fuse to the turn signals and it is good and the turn signals work.

both relays show 16ohm across + and - so it's possible both are bad relays since that should be 50ohm, but why am I getting continuity from the horn hot terminal to ground only when the relay is plugged in.

This is hard to isolate because the horn hot of terminal 5 is only hot when the relay is plugged in because that is where the hot to the horn button comes from.

So there is no continuity without the relay plugged in but there is also no power. Without the relay there is no continuity between the hot and ground of the horn button so what would I expect to find under the horn area with the turn signals? If the short was in the turn signal area it would always show continuity.

That can't be the short. So it's shorting to ground through 2 different relays suspended in the air?

The problems I've had with the horn before ended up being the ground mount for the horn itself. This time something else is wrong.

When it's working I can just short across the hot terminal to the steering wheel bolt and engage the horn. Now I'm getting constant continuity between those two terminals but only with the relay plugged in.

But the relay doesn't even have a ground so I'm puzzled.

I should mention that with the relay plugged in I get 12v between the hot horn button and ground. Plus I get continuity. Maybe it's a false continuity.

Should I try a third relay?



Horn relay

Relay plugged in

Horn button

Sketch

 

I don't see any information on the vehicle...

Year, model, gas, diesel, etc...

 

'69 e200 Econoline gas v8 5liter

 

I unbuckled this harness and it looks like the short to ground is on the horn side, not the steering wheel side. The blue yellow is the hot going to the horn and it also has continuity to ground. But the blue yellow to the steering wheel only has continuity to the hot button, not ground.

Harness

 

Now I'm thinking the new relay was bad too. Not only is there only 20ohm between +/- when there should be 50 but I plugged everything in and then positioned the multimeter between terminal 1 to the horn and ground. Then I shorted the horn hot button to ground and read 9v at terminal 1 BUT the relay never clicked. The only way terminal 1 should read anything is if the relay closes but I read 9v when I short the horn button and horn does not work but the relay never clicked. I'll open the new relay up to see if it is stuck closed.

 

This is what you get with cheap NOS from last century. It's not stuck but it's all oxidized.

 

I'm still puzzled after cleaning this relay. I still get continuity between the hot horn button and the steering wheel ground so I'm doing something wrong because the horn seems to be hot wired always on but it's not working until I short it with a battery.

And I'm not sure if 20ohm is bad because nobody tests a 3 terminal relay since they are phased out. Seems suspicious both relays test at 20ohm between the coil.

If someone could test the resistance between 2 and 5 on their 3 pin horn relay that would give me some Intel.

And when the coil is energized I'm getting continuity 1 and 2 so it's working.

But why is there continuity to ground?

 

I did not carefully read the entire post. But here is the wiring diagram for the horn relay. The relay is turned on when the horn button is grounded. 12v from the battery goes through the relay contacts and sounds the horn.

If you measure voltage at the blue-yel wire it will show 12v. It drops to GND when the horn is pressed.

You can use any automotive relay and wire it the same as the diagram. You would put 12v on the coil and 12v on the normally open terminal. The horn is connected to the common terminal. The horn button is connected to the other coil terminal.

 

Yes I think I will find a generic 4 pin relay and make my own wires to it. They are $7.

But something is wrong if I've got constant continuity between hot horn button and ground. The horn should be blasting as soon as I plug the relay in.

 

No progress as I eliminate all possible faults.

I polished my horn surfaces with no change.

I installed a 4 pin 12v horn relay from my truck with custom wiring.

No change.

Then I installed a 12v horn from my motorcycle.

No change.

Steering wheel wiring


Then I pulled the steering wheel and polished the spring loaded hot even though i had power on the other side where the horn frame is.

If I can't get 3 relays to work then I'm starting to think the entire steering column is not fully grounded, even though I can get 12v between the hot and the steering column it doesn't mean I can get current to flow so when I close the connection between horn relay hot and ground I'm not getting any current.

I will rig a separate ground wire near the horn hot and see if that works.

 

Indeed, I ran a separate ground from the battery to the horn area and shorted the hot horn button back to the battery and the relay worked and the horn worked

So I looks like the steering column is grounded enough to show me 12v between the hot and the steering column but it is not grounded enough to use for the horn circuit. The hazards and the turn signals are grounded differently so they work fine. Only the horn uses the column for a circuit ground.

 

Are you sure the ground is making it through the steering wheel slip rings through that spring loaded contact?
That is the ground that controls the horn relay
You ground that pin and the horn honks right? or does it not?
That is the ground that closes the contacts in the horn relay

 

So, that 12v copper spring loaded pin ordinarily would ground against the steering wheel frame back through the center bolt and get the horn to blow. But NOW I have 12v between that spring loaded pin and the steering column BUT it doesn't activate the horn. If I bring a ground straight from the battery and touch the pin then the horn works.

So, it was a tricky troubleshoot where I had 12v between two points and thought the ground was good enough but it was only good enough to read 12v on the multimeter and now that I probe around the column I'm getting intermittent continuity. It's good enough to read 12v but not good enough to use as current for the relay.

I should mention that the vehicle was a surfer's home for years in Los Angeles and he would wear his wetsuit while driving and the salt water ate the floorboard and near the column. Which wouldn't be something you immediately think is causing a horn problem but with this wiring it's actually the path to ground for the steering wheel to the steering box. So what I will do is clean up all the bolts and the bottom screws and maybe run a wire between a bare spot and a better frame bolt to guarantee continuity.

floorboard

 

Nice troubleshooting. Enjoy your piece of history!

 

It looks like the whole problem starts at the Cclip Ring. Below that I get continuity to ground. Above that where I need it I get just enough continuity for the multimeter but not enough to run the horn. So I'm cleaning that area.

Steering column