nova10502

Which is the fuse for the horn?

Hazard15301

iTrader: (5)

If you still have the fuse box cover, the horn runs through the STOP fuse. But if your brake lights are working then its not the fuse. In that case check out this thread.

nova10502

OK I checked the fuse thats fine
I tried to jump the horn connection and ground to car no horn
I do hear a clicking coming from the cpu, maybe the relay trying to work
If it is the cpu can it be replaced and where do I get one
86 rx 7
Thanks

HAILERS

IF you hear the relay in the CPU click when you press the horn button, then that means the ground on the horn button is doing its job and that the fuse is good.

So you now pull the upper plug off the CPU and jumper a wire b/t the Green/White wire and the Green/Red wire.

The Green/White is power and is the same power that pulls the horn relay in. The Green/Red goes directly to the horns. They should blow if you jumper those two wires mentioned above.

nova10502

If it doesnt does it mean the cpu is bad
and if it does what do I check next

pfsantos

iTrader: (1)

Not sure if line 2 in the OP's post refers to checking the horn switch or horns themselves...

Did you check if there is power at the horns themselves (test light or multimeter)? Try applying power and ground to the horns.

Lastly, odd story, but could be your problem, although very unlikely:

I once half stripped my car (for painting) and switched the plugs between the horns and the A/C system filter/dryer (?!) because the plugs are similar. Had to wire the horns directly with a separate wire. About 2-3 years later, I'm adding gas to the A/C system and notice the pressure switch isn't hooked up...look down and the plugs (two separate one wire rubber plugs) are on the horns. BTW, the horn plugs are straight, the A/C pressure sensor ones have a 90 degree angle.

nova10502

Just jumped the 2 wires and the horn blows
WHat do I check next?

nova10502

Horn doesnt work and I can hear ckicking in the cpu
I jumped gr/wh and the gr/rd on the cpu and the horn blows
WHere do I go from hear
Is it the cpu or something else

Icemark

Bad relay in the CPU or bad solder connections. If you want to try and fix it yourself, remove the CPU, take the screw and panel off the back of it and re-solder where all the pins that the plug plugs into meet the circuit board.

Remember to resolder the board, you need to first remove the old solder with either solder wick or a solder sucker. if you just re-heat the connection you have not removed the corrosion from the joint and may (if you are lucky) intermittently have fixed the problem.

nova10502

Thanks for the help

Icemark

any particular reason you felt the need to start three threads on this? Threads merged.... only start one thread per subject per member

nova10502

Sorry
I know for next time
Thanks for your help

boosted1205

iTrader: (9)

I've had to use a relay on a customers car because the 2 CPUs he purchased were bad. It's a simple procedure. Buying used CPUs are hit or miss and 90% of time it's a bad CPU.

nova10502

CAn I just replace the relay
They do sell just the horn cpu at Mazda trix for 119
Maybe I should just buy it.

Icemark

YOu can get the relay from digikey, but it is soldered to the board, so you still need to unsolder the old one, solder the new one in. But the majority of the time it is due to the CPU board connections more than the relay, so you often don't have to replace the relay if you re-solder the board as I described.

nova10502

I pulled the board and the joints look clean
DO I need to unsolder both relays?

Icemark

Yeah, I am sorry I guess I wasn't clear... you need to remove the old solder and flow new solder in where the pins for the plug meet the board. It doesn't matter if the joints "look clean".

HAILERS

With the plug on the CPU, wiggle the wires on that connector WHILE pressing the horn button. It the horn honks when you do that. then it almost has to be cold solder joints on the jack of the CPU where that connector connects to the CPU.

Kalle

I´m having problems with my horn. I have tried to jumper the g/w wire and the g/r wire without success. If I connect the g/r directly to the battery the horn blows.

I have 12 V on the g/w wire. Also I hear no clicking in the cpu when pressing wheel. Brake lights does work. And I cant find a signal between the g/w wire up by the steering wheel and the g/w wire on the CPU plug. The only wire I get signal from on the steering wheel is between the g/y on the steering wheel and the small g/r on the cpu plug which is very strange.

I have no ECU connected if that makes any difference

satch

iTrader: (1)

Where are you trying to jumper the G/W and G/R wires? Is it at the CPU's largest plug? If the G/W has power and you jumpered the power to the G/R wire and the horn did not sound then the jumpering is improper because you stated that when voltage is placed to the G/R wire the horn sounds.

Now there is no G/W wire by the steering wheel as it pertains to the horn. The G/W wire for the horn is 'only' found at the CPU. The wire at the steering wheel for the horn is Green/Orange and this wire is supposed to provide a ground signal to the horn relay in the CPU when the horn button switch in the steering wheel is depressed. When the relay receives voltage on the G/W wire and a ground on the G/O wire the relay should then send voltage to the G/R wire and sound the horns.

Thus at the largest plug of the CPU you should jumper a Ground from the Black wire in this plug to the G/O wire found between the G/W and G/R wire and the horn should sound. If it does then your problem is at the horn switch in the steering wheel.

Kalle

Thank you! Yes I am doing this on the CPU´s largert plug, the black upper one.

Well it´s weird cause like I said I do have 12V att G/W but when i jumper it to G/R I get no reaction. The horn only sounds if I connect G/R directly to the battery or some other 12V source.

I´ll try jumpering from ground to G/O tomorrow. Thanks again!

satch

iTrader: (1)

If you jumpered voltage to the G/R wire then you should be able to measure the voltage w/a meter at the wire jumpered to, which in this case would be the G/R wire. Also, there's a possibility of two G/W wires in this plug (one would be at the very end of the plug while the other is found between the G/O and a White/Black wire. You would know which is the correct G/W wire for the horn for that G/W wire would lose power once the stop fuse (20 amp rated fuse) is pulled.

Kalle

Thanks for all the help. I´m still having problems though and I´m super confused. This is what I´ve tried so far.

- I don´t get any reaction in voltage-change while pulling the STOP fuse on ANY of the wires.

- There is ONE wire on the plug that is G/W and this one has 12V constantly. However, when I jump this connection to G/R I get no reaction, the horn does not blow and the voltage drops to 0V.

- If I put battery 12V to the G/R the horn works.

- I´ve jumped the Black to G/O wire, No reaction.

- I´ve tried with two different CPU´s.