Gabriel82

iTrader: (8)

Hi everyone,


Here are the recent things I did to my FC:
New Battery Terminal Covers
Installed NRG Quick Release


Earlier today I started my car and drove it down the street to the car wash. Before even spraying the car with water the horn started sounding (Ignition was in the ON position). I figured it was one of the cables in the hub making contact since I recently installed an NRG quick release. I wiggled them around and the horn kept going. It wasn't until I disconnected the horn closest to the radiator that it stopped. I washed the car and jumped on the highway and the horn came back on. This time it was coming from the horn closest to the bumper, right under the reservoir tank. I got home and turned off the motor and the horn kept going. As I disconnected the remaining horn I noticed that my headlights and fog lamps turned on (headlights did not flip up). I turned the ignition to OFF and the headlights and fogs turned off. When I switched the ignition back to ON the headlights turned on. Could the horns need to be replaced? Is that an issue that can arise?

Gabriel82

iTrader: (8)

I did the check the brake lights and confirmed they are working. So I can cross out the fuse as being the issue.

Gabriel82

iTrader: (8)

Update: I fiddled with the car this morning.

Disconnected the negative cable on the battery. Disconnected the whole CPU. Connected the horns and CPU again. Connected the negative cable to the battery. Boom the horn worked again. Put the ignition in the on position and the horn worked with no issues. Didn't keeping going after I pressed the horn button. Lights didn't turn on either. I guess the car was just being moody??? I still replaced the horns with Hella Supertones.

Gabriel82

iTrader: (8)

Hey everyone,

The issue came back. Now as soon as I start the car the horn goes off. Not sure if it's a bad ground? The hella horns are being grounded to the same location that the OEM fog lamp relay sits in. There is still paint there.

professionalpyroman

have you had a look inside the horn computer to see if something is goofed? If it's related to both the horn and lights, it could be a short in the alarm cpu

Gabriel82

iTrader: (8)

I actually found a write up on it. I'm going to clean the contacts. I'm considering re-soldering the CPU contacts and changing out the relays. Not sure if that's overkill but I can't find which relay to use on the CPU.

Gabriel82

iTrader: (8)

I took the CPU apart. Used electrical contact cleaner. Resoldered the contacts.

Installed everything in the car. With the car off I pressed the horn and it worked no issue. Turned the car on and for a few minutes no issue what so ever. I honestly thought the problem was fixed. But I spoke too soon. The problem came back. Horn going off. I had to run to the front of the car and immediately unplug the power going to the horns.

Pretty frustrated. Hoping someone has a solution.

professionalpyroman

This is old tech, it takes patience.

Did you happen to have a look at the capacitors on the cpu board? What condition were they in? My car alarm started triggering on its own when the caps in my cpu started failing. These electronic components have well exceeded their age and cycle limits.

If the horns are still going off when connected, disconnecting them should allow you to trace the voltage. Route out your points of inspection on the wiring diagrams. You won't be looking for a ground fault, but points where the voltage could get stuck on via switches, transistors, diodes, etc. Is there a sensor related to the car alarm that is grounding out or triggering the horn/car alarm circuits? The sensors could likely use a good cleaning while you are pondering the solution anyway. Trace the voltage to the supply, and then figure out what is engaging the supply.

Gabriel82

iTrader: (8)

So tonight I went and disconnected the power running to both horns. With the ignition on, I noted 12v for each connector. Shortly after the headlight and fogs turned on (Headlight did not go up). I kept hearing a click from the headlight relay. I wiggled it a bit the headlights and fogs turned off. Checked the horn connectors and 0 volts. So i'm going to change the relay tomorrow and spray some electrical cleaner on that headlight relay connector. I'll report back.

Gabriel82

iTrader: (8)

Update: So I cleaned the crap out of the connectors (headlight relay connector and positive connector to horns) using a toothbrush and electric component cleaner. Then I changed out the headlight relay with another oem one (H302-67-740 12v 20amp 5pin Blue $16). I had to buy the relay on eBay since the representative at Mazda didn't want to help. I let the car run for 25min with no issues from the horn. During that time I switched the headlights on and off. I took the car for a drive and randomly honked the horn to try to get the issue to reappear. So far so good! no issues what so over. I shall say I am a little traumatized waiting for it to go off but I'll give it a few drives and I'll see what happens. I did order the CPU relay(Siemens V23072-C1059-A208 $14) and I'm going to switch that out as well.

pfsantos

iTrader: (1)

Hope it turns out fixed. Make sure the wiring to the horn switch isn't chafed or has been cut or squeezed when you did the steering whee. I believe the horn CPU looks for a ground. If there's any insulation missing and it touches on the steering shaft or hub, the horn will sound. You know about the CPU soldering and relay issues, so hopefully that's not it, and if it was, it should be ok now.

Story time:
I once did some work on the car (bumper and some panels off) and ended up swapping the connectors between the A/C pressure switch and the horn by mistake. Ended up running a wire straight from the horn switch (tapped under the steering column), past the firewall, to the horns. Years later realized my mistake when I filled the A/C system and it didn't want to work. Found the A/C switch unplugged.

Gabriel82

iTrader: (8)

So far so good. I keep expecting the horn to go off any minute but nothing at all which is a good thing. At first when the issue started I took the steering wheel off and checked those wires to see if it was making contact. That wasn't the issue. I started hearing a lot of clicks randomly from the headlight relay without the headlights being triggered. This was with the horn disconnected. I did notice the headlights would turn on so I checked the voltage for the horns and saw it go from +12 to 0 randomly. The relay was worth the shot and I think that was the issue. I do have the CPU relay coming in. I'll change that out for safe measure.

Gabriel82

iTrader: (8)

Update the horn problem returned again.

I switched out CPUs (luckily I have a few extra from donor cars). I cleaned the plugs that go into the CPU. Let's see if the issue lies within the OEM CPU.

professionalpyroman

Did you fix this? Was it the CPU or possibly an input?

Gabriel82

iTrader: (8)

I ended up switching the CPU for a spare I had in my garage. So far so good. I haven't got around to changing the horn relay within the original CPU.

professionalpyroman

I was thinking something kept triggering the alarm function in that board. Here's the post to where mine failed. The capacitors had failed and were eating away at the circuits. Take a look at yours and see if you have some of the same issues. https://www.rx7club.com/2nd-generati...istor-1125858/

Its always good information on here when somebody finds the root cause of their problems. Electronic gremlins especially