Aux tank guage

I hope this has an easy answer. My aux. air tank guage goes to 0 almost immediately after turning bus off. However no leans. If the ignition key is turned on immediately see the normal pressure. The aux. air compressor only goes on everyother day or so. If I leave the aux. compressor off then the pressor will read lower than normal with ignition on. that pressure drops as use the toilet, or air pocket doors etc which is normal.

I hope this is normal (guage only working with ignition on) since everything else seems okay.

Thank you for any information.

Kim Sloan
02 Vantare XLII S2
06 Dodge Megacab

Doc,

That's kind of strange, they must have the gauge tied into a pressure switch of some kind. Sounds like your aux system is holding up pretty good since the aux compressor runs so little. Mine has a gauge that reflects the tank pressure with no relation to the key position. My vintage Marathon has the gauge in the steering bay and I'm going to add one to the dash.:rolleyes:

Hello tom,

I know it is strange, but there is almost no ther explaination since the aux. compressor runs so little.

Kim

What exactly do you mean when you say almost immediatly? When you turn the key off it doesn't immediatly go to 0. It hangs there for a few then drops immediatly to 0?

I'm curious because all the air guages I'm familuar with are mechanical.

Some are electric? Mabye digital?

Kim, I typed you a big long post and the keyboard fell out of my lap and some ??key got bumped and everything went away. Lucky you!

So in a nut shell. Is there a mechanical gage in the compressor compartment? If not add one with a Tee Fitting in the pressure line.

If there is one, does it reflect the dash gage, when on and off?

I think not, probably only when on. Not likely to go to zero when ignition is switched off. Pretty hi-tech though, to control the gage with ign. switch. Probably more trouble free and easier to install wires than air lines.

Look in the compressor area and see if there is a pressure transducer in the pressure line. It would have a wire or two going to an electronic dash gage. It would look something like an oil pressure transducer. If you see something like that then you are electronic and not mechanical and the going to zero with key off is OK.

If it is easy to see under/behind the dash to view the gage to see if it has wires or air line to it, would also tell the tale.

I know you want to know if everything is OK, but I am guessing that it is.

You have had several probs. in a short time and you are probably nervous.

Keep an eye on it have a few bones and enjoy the weekend.

:D :D JIM

Good morning Jim,

Here are some of the answers. It goes to zero within 1 minute after hanging at 30lbs for a few seconds. There are the wires and transducer. Therefore it seems that it is electric, and hanging for a short time (reason?). that being true it seems everything is okay with system since no leans and with key on immediately reads over 100lbs.

Kim, after reading your post, it seems there must be some kind of low current at the gauge. When you turn the key on, check voltage at the sending unit, I think you have already found it. Then turn the key off and check the volts before it goes to zero. If you have a lower voltage, its probably some low voltage backing in from another source. You might need a diode in the line.

Keep in mind I have no Idea of your setup.

I'm not sure but I'm assuming that the pressure in the aux. tank should be no different than the primary or secondary pressures one. We do not even sport a aux. tank guage.

There those pescky engineers go unnessesarily complicating things again:rolleyes:

I wonder how your other two guages are set up elec. or manual?

Joe, My rear brake tank has a manual guage and the front brake tank has a electric guage. I think someone must have changed one at some time. I think the bus came out with electric from the factory, then went to a manual gauge. I don't have a aux. guage on the dash.