OK first off if someone has solved this problem already im sorry for making a new thread..but i couldnt exactly find what i needed after searching. so anyways the other day i found that my horn was randomly going off and my headlights were on. the horn was completely steady though not honking with the standard alarm interval so i figured that ruled out factory alarm. but anyways. what would cause my alarm to go off and my headlights to come on at the same time.

 

If your alarm were to go off would the headlights come on?

 

The Meter fuse powers your alarm so when the time is opportune pull this fuse and see if it prevents the lights and horn from turning on. The horn uses the Stop fuse which is normally independent of the headlights and the Meter fuse with the exception being the alarm system.

 

What kind of FC do you have? From your picture you show a convertible. What series?

 

Bump. This was just happening to my car randomly yesterday and the neighbors where it was parked called the police. They called and when i got there the horn was going off the lights were on and I had a ticket on my window for horn not turning off within 5 minutes... I tried to start it and it wouldn't at first like the battery was low, thew horn was still going off so I disconnected the battery. I reconnected it and the horn still went off so i disconnected the two horns in front of the front reinforcement. Then it started and after driving for a while when i turned it off it was done. I disconnected the battery so it wouldn't happen while I was away.

It is a 1990 s5 convertible. Anybody solved this issue before?

 

relays get wet by chance??...similar things like this have happened to FD guys with their horn and headlight relays getting wet. Sounds like your alarm got triggered somehow

 

S5 vert alarm/high beam issues will be fixed by new CPU.

 

I thought it could be that. hmm.. it was raining yesterday. You think they will need to be replaced?

 

I had intermittent no start issues when I first got my vert (now that I think about it, it was most likely the CPU shorting out). A new CPU did wonders. Open your CPU up, look at the board. If you see leaking capacitors or components or burnt up components, order a new one from mazdatrix, it is redesigned compared to the old unit.

When the alarm is going off, you have to lock/unlock the drivers door to turn it off. Did you do this? Your issue can also be bad door/trunk/hood switches for the alarm, but you will known once you look at the board.

 

The first thing I did was unlock and lock the doors, it kept going. I didn't know the car had an alarm. On my fd the lights go up and down and the horn honks. This was different, the lights stayed down and were flickering and the horn was on constant but not normal it was flickering with the lights. New CPU seems like what i need.