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cat938g 10-22-2011 10:23 AM

Air horn problem
Good morning. I have a 36' RexAir diesel pusher with airhorn problems. The horn is intermittent, not working more than
working. Don't think I have a town horn or i can't find it. No
switch on the dash to change from town to air. I really am a
newbie and could use some help. I have only put 350 miles
on this coach from socal to Lodi. Any help? The coach is a
2004 if that helps. Thanks in advance ....Bill

bigskymt 10-22-2011 10:56 AM

Your horn is probably activated by a electric air valve powered by the horn button. If you can trace air lines in the front you should find an air manifold that will supply your horn valve. At least that's the case with my '04 Freightliner Chassis.

GMRHost 10-22-2011 11:08 AM

If the Air Horns have "bells" covering them, your problem is likely as above. If they are open-trumpets, make sure to get up where they are and give them a good cleaning, preferable with a good strong stream of water inside. Bugs will cause all sorts of woes with them, making them either puny sounding or non-operative.
As obnoxious as this sounds, they should really be "blown" every time you drive it. Most people are skittish about this, since there are not many times where there is no one around to wonder why the heck you blew them, lol...

njs42 10-22-2011 11:26 AM

Air horns are simple---a compressor fills a tank to pressure, a solenoid valve opens when you activate electricity to it--air flows from the tank then to the horn which has a diaphram which vibrates to make the noise.

Find these components and eliminate them as a problem.

Intermittent probably means electrical---if it were a solenoid not working then it probably would not sound at all. It cannot sound if it does not have air pressure to the tank or if the diaphram is not working---so that seems to eliminate the solenoid and the compressor and the tank and the diaphram.

You should have a dash guage for pressure if it is good then the tank and compressor are fine.

Solenoid valves can be on the horn or somewhere mounted near the tank or on the tank or on the body of the MH. Follow the air lines to find them. They are abvout the size of an old 35mm film can. Two wires and an air hose in and out.

Maybe a bad contact somewhere----a short---a bad ground----or a bad horn button contact----the difficult part is finding it. Unfortunately electrical is the most difficult to diagnose---a good wiring diagram helps---a continuity checker and a multi meter help.

Yes, yes I know my 2003 Dolphin does not have an airhorn---I installed one---you diesel guys can't have all the fun.

Incidently a town horn is not difficult to have nor expensive--and Hadley makes a really nice one---for the future after you solve this dilema.

Good luck to you---if I can help more I wlll assuming this is helpful if not then use your delete.

cat938g 10-22-2011 04:26 PM

Thanks to all who responded
Thank you all for responding.... I traced it to a bad relay. $18 later
all is good!

GMRHost 10-22-2011 06:14 PM

Good job, friend! Wish they were all that simple!

njs42 10-22-2011 07:07 PM


Now that you have solved your problem and done some chasing of wires. Here is a link to the Hadley electric horns if you want a town horn---I replaced my anemic Fiams in my Dolphin with these and they give a very perfunctory beep beep. A simple toggle on the horn button hot and then wires to your "hood" area would give you a town horn.

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