ojsmithj

The fluctuation, when it occurs, is rapid and sometimes only occurs on one gage. Then at other times both gages fluctuate but not at the same rate. I strongly believe I have an indicator problem and not an actual loss of air pressure. I also think the air pressure gages are direct reading and not electrical.

If the governor was freezing wouldn't both gages fluctuate together, i.e. read the same at the same time? I drain the air tanks about every 6 months but have not serviced the dryer.

There are 2 separate indicators, both with black pointers. They fluctuate separately. Some times only one gage drops off to 0 and then some times both are erratic. But in all cases the fluctuations are not synchronized. On startup, they both fluctuate until system pressure builds up and then they stabilize. They remain stable for awhile, some times as long as an hour or more, and then begin to fluctuate. That may last for a minute or two or some times up to five minutes.

I have requested the info from Fleetwood but have not had a reply yet. Is there a possibility that the air pressure gauges are direct reading sense the "red" and "green" air lines go directly to the back of the gauges?

I need help locating the "VDU" or "MMDC" on my 2007 Excursion with a CAT engine. I am having the same problem with both air gages reading erratically intermittently resulting in the low air pressure alarm sounding. I have reviewed all of the posts on the subject and agree that it has to be an indication problem as the brakes and air bags operate normally. My problem is finding the "VDU" or "MMDC". I traced the red and green air lines from the large valve located under the coach behind the left front wheel up to the back of each air pressure gage and there was not a "box" in that run. There is a compartment on the curb side behind the rear wheel with a decal on the door that reads "ATTENTION VEHICLE ECH, VIM, VDC LOCATED IN COMPARTMENT". There are 2 boxes in the compartment, one with a large 2 on the cover and the other with no markings. Neither box has air lines attached to it. I have searched the engine compartment, under the bed and under the chassis from front to rear without locating the subject box. The VIN# is 4UZACJDC57CY89100.