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Author Topic: Air Horn Problems  (Read 2131 times)
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Jr. Member
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« on: March 23, 2011, 11:26:42 AM »

After never having a problem with the air-horns, they suddenly cut-out after the first of 2 blasts - now nothing !
Have tried the obvious things:
- Fuses ok.
- Tried hooking the compressor to a 12v source direct, and it work ok, but nothing when wired in.
- Can hear the solenoid clicking in ok, Tried a new relay anyway, still nothing.
- Tried a spare compressor, made no difference.
- Stuck a multimeter across the wires leading to the compressor and seems to be reading 10-11V when the horn button is pressed.
- Tried measuring with the compressor wired up, but couldn't get a reading.

Anyone got any thoughts on the next troubleshooting step to try ?

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Peter Stokes

« Reply #1 on: March 23, 2011, 11:39:02 AM »


This may be a case of a bad crimp causing a high resistance along the supply cable from the 12V source via the relay and then to the return circuit (however that is setup). The reading on the multimeter may look ok, but in fact be an oscillating one, ie when you push the horn the actual voltage may be varying up and down and averaging out to 10V.

What I suggest is as follows

1) Link the multimeter (on DC volts) from the Gnd side of the compressor to the -ve on the battery and with the horn pushed in, see if that gives a firm 0V or has a value > 0. This would point to bad ground.

2) Assuming 1) is ok, link a temporary wire from the following points and check if the compressor runs

  a) Direct from the battery
  b) From the live side of the relay
  c) From the side of the relay which is already connected to the compressor

This should resolve where the issue is, if wiring. Obviously assumes the compressor is good....


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« Reply #2 on: April 02, 2011, 09:00:26 AM »

Thanks Peter

Followed your suggestions and found the problem in the wiring, all working perfectly again ... for now  Smiley

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