early FJ40 horn relay wiring (1 Viewer)

[Krondor]

I purchased an early replacement horn relay but am having trouble finding out the correct way to wire it up.

Here is what I am working with:

New horn relay form city racer and a 1965 FJ40 wiring harness with a green white (GW), Green red (GR) and Green Yellow (GY) wire.

 

[Stormsd]

I purchased an early replacement horn relay but am having trouble finding out the correct way to wire it up.

Here is what I am working with:

New horn relay form city racer and a 1965 FJ40 wiring harness with a green white (GW), Green red (GR) and Green Yellow (GY) wire.

View attachment 2653590 View attachment 2653596

Just starting to look at my inoperable horn on my 69 (11/68) build. I know gw goes to the horn itself and gr to the horn button. Gy goes to the fuse panel through RB wire at least according to wiring diagram and as i see it in my 40. Those letters are confusing. Have you tried hooking them up in the order removed? I would try GW to H, GY to B and GR to S. Someone else who is certain hopefully chimes in here and helps us both

 

[locklaw]

Just did this last week. GW twin wires to the horns (H), (B) is battery positive and (S) is the wire to the horn button (it makes a ground when pushed, thus negatively switching the relay on). I forgot which color exactly but think GR went to the horn. Use a test light or multimeter to check which has positive always on power, that goes to the middle.

 

[73FJ40]

Those letters seem to be spot on to me: H = horn, B = battery, S = switch.

If there's any doubt in the wiring, a volt ohm meter is your arbiter:

The horn relay wire with 12 volts positive goes to the relay's "B" post. The horn is always energized, so this wire should be hot at all times.

The horn relay wire that has continuity (0 ohms) to the horn connector goes to the "H" post.

The horn relay wire that has continuity to ground when the horn button is pushed goes to the "S" post.

Inside the horn relay, the battery power feeds one side of the relay coil all the time. The horn button provides a ground path for the relay coil when it's pressed, and energizes the relay. The contacts on the relay feed power from the battery power to the horns when the relay is energized.

 

[middlecalf]

GR to S terminal, GY to B terminal, 2x GW to H terminal

 

[Kschep]

GR to S terminal, GY to B terminal, 2x GW to H terminal

What year is this for?

 

[middlecalf]

At least a ‘63 and a ‘65.

 

[Stormsd]

At least a ‘63 and a ‘65.

I just followed these instructions on my 68’ as well. Worked fine

 

[ERNRAM]

@Coolerman
Aka Mark

I got me a mystery.

Have a new cityracer relay. Screwed it to the fender and wired up the 3 wires

So if I wire as shown above, I will blow the horn fuse at the fuse box. So I did an experiment. I unplugged the S ( signal from the horn) and the H (horn wires). It still blows the fuse.

If I do not screw it to the fender, and isolated it with some rubber, then with the same wiring, it will not blow the fuse and the horn works.

 

[B y r o n]

@Coolerman
Aka Mark

I got me a mystery.

Have a new cityracer relay. Screwed it to the fender and wired up the 3 wires

So if I wire as shown above, I will blow the horn fuse at the fuse box. So I did an experiment. I unplugged the S ( signal from the horn) and the H (horn wires). It still blows the fuse.

If I do not screw it to the fender, and isolated it with some rubber, then with the same wiring, it will not blow the fuse and the horn works.

Sounds like there is a short to the case inside the relay.

 

[ERNRAM]

Makes sense.....a new failed relay

 

[ginmtb]

I have had some fun with my horn. Maybe this will help? This is the Coolerman test:

Disconnect EVERYTHING from the relay. Using jumpers, apply +12V to the B terminal. Does the relay click? (It shouldn't) if it does then that relay is grounded through the case and is not the correct relay. You can still use it but you will have to isolate the relay case from ground with some type of insulator.

If it does not click then using a jumper, ground the S terminal. Relay should click and you should measure +12V on the H terminal. IF that works then connect the horns back to the H terminal and again ground the S terminal. Horns should blow.

 

[ginmtb]

Also, Toyota changed the wires for the horn relays at a certain point. Check out my post here - Builds - Won a '74 40 on a coin toss... - https://forum.ih8mud.com/threads/won-a-74-40-on-a-coin-toss.804579/post-14708049