Air Horn Sounding when Starting Engine

[Mark Bryant]

Coach has been in storage since end of March. Started engine to give it 20 mile run to warm Trans oil for filter and oil change. When strarting engine the air horns sounded, not knowing why, discontinued start and horns quit. Started engine again, engine started and horn sounded again for maybe 10 to 15 seconds and quit. I'm thinking that because the air was low that horn is a warning?

Hearing the horn is not what I expected starting engine!!

Hope there is a reason!

2006 Monterey

[Gerald Farris]

Mark,
The air horn should not sound when starting the coach. Normally unexpected sounding of the air horn is caused by a malfunctioning Smart Wheel control module. However you will have to troubleshoot the system thoroughly to determine the problem.

Since the air horn will not function at all without air pressure, using the air horn to warn about low air pressure would not be a good idea. Besides, when the air horn is blowing, it is using up what little air pressure you have in the system.

Gerald

[Mark Bryant]

Thanks Gerald!

When I restarted the engine after changing trans oil & filter the horn did not sound. Still will check the system out.

Thanks again!

Mark Bryant
06 Monterey

[Richard And Babs Ames]

Are you sure it was the air horns and not the low air warning signal.

[Bill Sprague]

There is a Smartwheel trouble shooting guide in the "Coach Assist" section at http://www.beaveramb.org/

[Mark Bryant]

Are you sure it was the air horns and not the low air warning signal.

When you are in Steel Garage you know its the HORNS!!! And low air warning signal was on, expected that.

Mark Bryant
06 monterey

[Gerald Farris]

Mark,
The problem that you will have in troubleshooting the system is the fact that the problem has stopped. Intermittent problems are the hardest ones to find. Repairing intermittent problems is usually not to difficult, because all of the work was done in the diagnosis, and the repair is just putting everything back together with a new part to replace the defective one. However you normally have to get the problem to reoccur repeatedly in order to properly diagnose the problem.

There are some problems in all automotive products that exhibit predictable characteristics when a part is malfunctioning, so the experienced technician can sometimes diagnose an intermittent problem without actually seeing it by just listening to your description of what happened. However there a a lot of problems that do not fall into the predictable bracket, and if it can not be duplicated the technician will have to use the old saying "I can't  fix it if it isn't broke".

Gerald

[Richard And Babs Ames]

When you are in Steel Garage you know its the HORNS!!! And low air warning signal was on, expected that.

Mark Bryant
06 monterey

Fully understand just covering all bases. Is the air horn pressure switch kept shut by air pressure and the air pressure had to build a bit to shut the switch because the air pressure had leaked down and the air horn button had bee pressed that left it open?

[Edward Buker]

I suspect that the air solenoid is a plunger and seat or needle and seat that is held shut with a spring. I do not think that the air being low would enable the valve to be on. The solenoid when activated overcomes the spring tension. The coach was laid up for awhile and it seems possible that the chassis battery could have been low and during cranking the smart wheel logic saw low voltage and that circuit was falsely triggered. When the electronic circuits are being run out of voltage spec (probably around 9V minimum) they can have a mind of thier own.  If once the coach was run a bit the probem went away then this could be an explanation. If the batteries were all well charged and in good shape, and the terminals all clean then this seems less likely.

Later Ed

[Mark Bryant]

I suspect that the air solenoid is a plunger and seat or needle and seat that is held shut with a spring. I do not think that the air being low would enable the valve to be on. The solenoid when activated overcomes the spring tension. The coach was laid up for awhile and it seems possible that the chassis battery could have been low and during cranking the smart wheel logic saw low voltage and that circuit was falsely triggered. When the electronic circuits are being run out of voltage spec (probably around 9V minimum) they can have a mind of thier own.  If once the coach was run a bit the probem went away then this could be an explanation. If the batteries were all well charged and in good shape, and the terminals all clean then this seems less likely.

Later Ed

Ed
I use a 50w solar panel on the roof of the garage to maintain my batteries, 13.1 was the reading when I started the engine. I'm going to clean all the terminals on the next trip to the garage.  Have downloaded wiring diagram from Vehicle Improment Products website.

Thanks for the INFO!

Mark Bryant
06 Monterey

[Mark Bryant]

Mark,
The problem that you will have in troubleshooting the system is the fact that the problem has stopped. Intermittent problems are the hardest ones to find. Repairing intermittent problems is usually not to difficult, because all of the work was done in the diagnosis, and the repair is just putting everything back together with a new part to replace the defective one. However you normally have to get the problem to reoccur repeatedly in order to properly diagnose the problem.

There are some problems in all automotive products that exhibit predictable characteristics when a part is malfunctioning, so the experienced technician can sometimes diagnose an intermittent problem without actually seeing it by just listening to your description of what happened. However there a a lot of problems that do not fall into the predictable bracket, and if it can not be duplicated the technician will have to use the old saying "I can't  fix it if it isn't broke".

Gerald

Gerald

I know what you saying! I spent the past 20 years working aircraft & engine development programs and have my share of "its working OK now" problems.
The good thing is that everytime one of these thing happens I learn a lot about the coach and find the necessary data or info to work the problem through.

Thanks
Mark Bryant
06 Monterey

[Gerald Farris]

Ed is right about the way that the air horn control valve is constructed. It is held closed by a spring and requires enough voltage through a solenoid to overcome the spring pressure to open the valve. So an electrical current had to be sent to the control solenoid in order for the horn to blow. The question is what caused the electrical current?

Gerald

[Mark Bryant]

If I find anything I diffently will let everyone know.

Thanks Again!

Mark Bryant
06 Monterey

[Richard And Babs Ames]

How about electrical current follows the path of least resistance IE through this valve switch becaue of a poor/loose ground somewhere. Something like the engine air charge heater comes to mind.