Chassis Air Gauge

talotto wrote:
Looking for advice. My "Front Air" gauge reads 100 anytime the motorhome switch is on, whether I've started the engine or not, whether air has built up or not. The rear gauge reads correctly - 0 when air is depleted and 110-125 or so (estimated) when the system is charged and cycling.

So, I'm thinking bad gauge, replaced the gauge. Same problem with the new one. The new one reads 100 PSI when on.

So now I'm thinking pressure sensor or wiring, so to test that I swapped the gauge input plugs (front gauge connected to rear wiring, rear gauge connected to front wiring). SAME SYMPTOM! Front gauge still shows 100PSI when powered - whether air system is charged or not, rear gauge follows the air pressure as normal.

There isn't a separate ground - it's all in the plug, and I swapped the plugs (as noted above).

In all of this the air system works properly, that is, the brakes work (i.e., release when aired, lock tight when not) motorhome drives and rides right, the chassis suspension bags air up, all appears to be correct ride height front and rear, side to side. No air alarm once the rear gauge gets above about 60-65.

So, any ideas? I know I'm missing something, but what?

It's a 2004 ITASCA Meridian, 36G Diesel pusher.

Tony

Tony,
We have the next model up, same year from yours. It's the '04 Itasca Horizon, 36GD with the C-7 330HP CAT. Now, your air gauges, are powered up by what's called the MMDC. Multi-Module-Data-Controller. The air lines enter into that MMDC and, are coupled with what's called a "Transducer". It basically changes a mechanical mechanism to an electronic one and then, sends it to the gauges for you to read.

Now, in our coach, that MMDC is located in the left front lower compartment, with a whole ton of other breakers, relays and more. On your coach, I'm not exactly sure where it's at. It's most likely in the cab and under the dash. Someone will chime in here with it's exact local.

Now, once you find it, here's little test. Bleed the air system down, almost to zero psi and then, to get those hoses, one green, one red, (front - rear) out of the MMDC, you simply push in on a small collar that's right at where they enter the box. That will release the hold on those hoses. If there's any air still in the system, it will escape when they're pulled out.

Now, just for grins and, maybe to check on our notion of a bad gauge, simply re-insert those hoses in the opposite holes. That is, put the rear hose in the front socket and, the front hose, in the rear socket. Now, if you do that, and you now get the opposite readings, i.e. the rear gauge is now reading what your fronts been reading but, your front is now performing perfectly, then you've got a serious projected cost ahead of you.

Those MMDCs hover around $450.00 plus or minus. But, if your front gauge still acts the way it does before the hose switch, then you've basically guaranteed it's the gauge. This is the one way I'd be checking the system out if, mine was acting like yours.

Grounds are the top rated cause when there's gauge and electrical issues. But, I don't think your issue is a ground. If you try this little test, let me know how it comes out will you. Good luck.
Scott