Community Forums

DieselOne · 07-07-2011, 05:16 AM

I'm new to iRV2 and I just bought a 1999, 38ft. Gulf Stream on a Freightliner Chassis. I am familiar with motor vehicles and will help fellow motorhome owners when I can. I have never had an air brake equipped vehicle before. The low air pressure warning buzzer does not sound in this unit. Can anyone help me sort out the test methods for circuits? (sensors, switches, buzzer/bell/gong unit, etc. or does anyone have a wiring diagram for that unit thay could share with me? Any help would be appreciated. Thanks

DieselOne

Fred Cooper · 07-07-2011, 10:19 AM

Get your vin number, then call the Freightliner Help Desk at 1 800 385 4357. They can look up your wiring diagram and give you some places to start looking. They were great to work with when I had a relay short out due to water intrusion. They will help regardless of whether you have remaining warranty.

On my coach, the sensor that turns on the low pressure alarm is located along the frame rail, drivers side, just in front of the rear axle. When mine failed, it would alarm when I had good pressure. Since you have no alarm, the sensor may not be your problem. It could be as simple as a fuse, loose wire, etc.

Fred

**RickO** · 07-07-2011, 10:31 AM

Welcome to the forum and congrats on your new rig!

I'll second the suggestion to call Freightliner Help Desk. I did for the first time a few weeks ago when I had alternator trouble passing through Albuquerque. I got a good ole boy on the line who was great to work with and really knew his stuff.

Rick

Dirtbuster · 07-07-2011, 07:12 PM

While talking to Freightliner, ask about their accessFreightliner.com It will give you a breakdown of the parts & drawings, of your chassis.

Good Luck!

Dwonner · 07-07-2011, 07:18 PM

Very possible that the previous owner was not a fan of the warning chime or buzz and simply unplugged it. Should be under the dash somewhere easily accessed.

Fred Cooper · 07-08-2011, 04:23 PM

Quote:

Originally Posted by Dwonner

Very possible that the previous owner was not a fan of the warning chime or buzz and simply unplugged it. Should be under the dash somewhere easily accessed.

Hmmm.. If you find it, let us know where it is located. I had my head under the dash for about 5 minutes with the thing going off and still could not get my hand on it. It sounded like it was very high up inside the dash, but I couldn't find it. Fred

DieselOne · 07-09-2011, 06:17 AM

Thanks for all the information everyone. I called Freightliner in Edmonton AB and they were able to guide me to the Low Air Sending unit. They informed me that the LASU is always located near the compressor. I was able to find the unit but the wires had been cut. Another, different-make sender unit had been installed nearby. In addition there appears to be another Air sending unit under the centre of the dash mounted on an air manifold located there. It may be the hi pressure cut off switch or any number of other air warning/signalling units. I'll investigate further. Thanks again, everyone.

DieselOne · 07-09-2011, 07:19 AM

I know I started out with trying to find the actual buzzer unit, but have moved to the sending unit now. The reason for this is that I found an Instrument cluster control module (Stewart Warner) with a built-in electronic buzzer/chime sytem down behind the carpeting to the left of the drivers feet with a cluster of about 50 wires coming out of it. Since the chimes work I reasoned that the buzzer should also work. The problem must be somewhere else in the circuits. At this time half the gauges in the IP have also gone to Full or top of their scale. Since the sending unit appears to be in relatively good shape, I believe the problem is a bad ground behind the front bumper for the gauges . With all of this happening at once the ground is the most likely culprit. Sorry for all the rambling, but I am reasoning as I type. All the suggestions I got has got me thinking. I'll post any results from my ground repairs. Thanks again to everyone.

DieselOne · 07-10-2011, 09:57 AM

The saga continues. The problem with the gauges turned out to be a bad connection at the coach batteries ground. Still no buzzer warning though. Will call Freightliner on Monday.

bigdog · 07-10-2011, 11:02 PM

Sure glad to find this thread as mine started coming on last week on our trip and at first I pulled over in a safe place,shut therig off and did a brake pump down.Old school bus driver and had to do that every AM.Started it up and let the pressure build back up.No buzzer..Next day,we're merrily going along and hit a bump and here it came again and did so intermittantly all the way home.Bummer.. Just had the air compressor replaced as the people who did it before I got the rig last year did it wrong and cracked the fitting where the pump bolts on to the engine and it was starting to drip oil.Sooo,I'll just have to take it back in and have the mech look at it. Also am trying to figger out why no air horn....

J Walker · 07-18-2011, 08:00 AM

Quote:

Originally Posted by Dwonner

Very possible that the previous owner was not a fan of the warning chime or buzz and simply unplugged it. Should be under the dash somewhere easily accessed.

Ditto. I bought mine new but I found that the buzzer was unplugged under the dash. BTW you should get a dash light as well as the buzzer if the pressure is low. If you get neither then you have a sensor or wiring problem. Call Freightliner, Gaffeny at 1 800 385 4357.

Fred Cooper · 07-21-2011, 07:37 AM

Quote:

Originally Posted by bigdog

Sure glad to find this thread as mine started coming on last week on our trip and at first I pulled over in a safe place,shut therig off and did a brake pump down.Old school bus driver and had to do that every AM.Started it up and let the pressure build back up.No buzzer..Next day,we're merrily going along and hit a bump and here it came again and did so intermittantly all the way home.Bummer.. Just had the air compressor replaced as the people who did it before I got the rig last year did it wrong and cracked the fitting where the pump bolts on to the engine and it was starting to drip oil.Sooo,I'll just have to take it back in and have the mech look at it. Also am trying to figger out why no air horn....

Exact symptoms that I experienced. Need to replace the air pressure sensor located on driver side frame rail just in front of rear axle.

Fred

DieselOne · 07-22-2011, 09:07 PM

I cured the "no low air warning buzzer" problem after I found some cut wires at the air pressure switch back beside the engine. I found an air manifold up under the dash near the steering column. It had a pressure sensor in one of its ports with two wires going into a wire loom. I did not want to cut any more wires so I went to the local Truck repair shop and bought a generic low pressure (55psi) Normally Closed switch and installed it in one of the manifold ports. I ran a hot wire from the ignition switch to one of the two terminals on the LAP switch. I went to Radio Shack and puchased an inexpensive 12V buzzer. I ran a wire from ground to one side of the buzzer. I ran another wire from the other buzzer terminal to the other still unused terminal on the low air pressure switch. The buzzer sounds load and clear upon startup and continues to sound until the air pressure is up to 55psi. When the buzzer goes silent is also when the red lights in the pressure gauges goes out. All is working well now. Thanks for all the suggestions. It is helpful to talk these problems through with all of you.