Air Horns going off

[Chris Hawes]

On Sunday, whilst the car was parked up/alarmed in the garage I could hear the air horns suddenly going off continuously. The alarm has its own siren and had nothing to do with it. I first checked the indicator stalk and pressing in the stalk for the horn didn't release it. I then went to take the fuse out (number 6) and it still carried on going off. I had to disconnect the battery to shut them up.

The day before the car went to South Wales and back with lots of fog/dew etc. Plus a load off ice flew off the top of a lorry hitting the front of the car (no damage) and wonder if there is a short at/around the horns themselves as they exposed to the elements. The twin air horns are mounted in place of the originals.

Could the ground have failed (would that cause the horns to go off continuously?)

I hope to get down to the garage tonight to investigate. Any help would be appreciated.

[bozzzydmc]

Hi Chris

Did the new horns come with a relay to take the load off the existing wiring? If so check the wiring around this area.

Regards

Mike

[Chris Hawes]

Hi Bozzy, yes, a relay/relays came with them.

Would a problem with a ground cause the horns to go off continuously?

[NickT]

Chris,

Did you fit the relay that came with the kit?? If you did, is it located near the horns under the car or (ideally) inside the car ??

If it is fitted outside and exposed to road elements, the relay contacts may have stuck closed causing the the horns would operate continuously.

Try temporarily removing this Relay and see if this stops the horns working continuously.

If it stops the horns then I would say that the relay probably has stuck contacts/ switchig problem. Check with a multimeter set to resistance and check across the pins with numbers 30 and 87. If there is a short here (with the relay removed) then the relay is duff and requires replacement. If the relay tests ok then there could be a short/ fault elsewhere. As the wiring in the Delorean is nominally negatively switched a short in the cable from the horns to an Earth point would operate the horn. The switched side would be on the steering wheel. If this has failed then the horn would operate continuously too. A check for this would be to physically fit the relay. If you can feel it click then the relay is being energised. As the relay should be energised only when the horn is pressed then you have the problem elsewhere.

Just to note,

When I mean negatively switched, the wiring would be as follows:

Battery Live (12v)
to
Fuse
to
Device (ie Horn)
to
Switch
to
Battery Earth (0v)

A positive switched device would be:

Battery Live (12v)
to
Fuse
to
Switch
to
Device (ie Horn)
to
Battery Earth (0v)

If someone has fitted a relay it could have been fitted as:

Battery Live (12v)
to
Fuse
to
Relay (Horn)
to
Switch
to
Battery Earth (0v)

OR (not ideal as the rest of the car is negatively switched!):

Battery Live (12v)
to
Fuse
to
Relay (Horn)
to
Switch
to
Battery Earth (0v)

If removing the relay does not stop the horns then the relay is not isolating the horns and so you have a wiring short around the relay base and/ or elsewhere.

Another point to note is that Fuse No.6 is not isolated by either the Main or Accessories relay so a fault will cause the horns to operate unless you disconnect the main battery.

If you do have a faulty relay then you would need to replace like for like. Even though they look the same and will physically fit, the relay pinouts are different. The European (ie DeLorean standard) is to have the relay coil pins 85 and 86 opposite each other with the switched 30 and 87 the opposite two with the blade connector at 90 degrees. American type relays have the the coil pins 85 and 86 next to each other.

Good luck,

NickT

ps just to reduce confusion, the term is "Earth" not "Ground". The word "Ground" is used by Americans.
Similar to "Live" (UK) and "Hot" (USA).

[Rottbott]

Chris Hawes Wrote:On Sunday, whilst the car was parked up/alarmed in the garage I could hear the air horns suddenly going off continuously.

I'm surprised I couldn't hear them from here.

[Tourettes Tony]

Trouble with your horn chris thats not what i heard :wink: TT