Leaving next Wednesday for Williamsburg. Coach has sat for couple weeks, so decided to start it up. Fired right up and front brakes pressured up to 125#. Rear brakes won't come up to pressure on gauge. Goes up to 10#. Didnt hear any leaks. Probably need to replace dryer. On my to do list. Confused why front would pressure up but not rear. Recent new D2, safety valves, pressure regulator on tanks and multiple fittings/ leaks repaired. Where should I start?
Maybe a check valve into the tank is stuck or maybe only a bad gauge. Try reversing the lines at gauge to see if you have the same condition or if it changes.
The drier would affect both tanks. You have a major leak in the rear brake system. If you can use an air compressor and hook it to your air chuck for airing tires you might be able to hear the leak. Too many possibilities to list them all until you can say which end of the coach it is leaking from.
Will block up and put air to coach tomorrow. Time to start crawling around underneath
There may be a check valve that will prevent airing up.
I put in an air chuck at dryer so I can hook compressor to coach and trace leaks. Found leak at hose from coach compressor. Actually at nut to compressor. Looks like leaking at threads to housing.
That leak would not explain one tank with normal pressure and one with just 10 psi.
Its handy in this type scenario to be able to know for a fact what pressure you have in each brake tank.
I put a male quick connect fitting on the drain valves for both brake tanks. Stuck a female quick connect fitting on a pressure gauge.
Pop the gauge on the drain valve, open the valve, you see exactly what pressure you got in that tank.
Easy way to diagnose a faulty dash air pressure gauge.
Chuck will follow up on your suggestion. Tank had pressure will configure new so gauge can attach. One of my new tank drains i replaced in February already leaks. Everything seems to be crap these days(chinese). Bonus is finding 2 air leaks.........so far
120# at drains on both tanks. Gauge?
I may have found out it is is the PSI sender unit. On order should know soon
Replaced sender unit on rear tank. Now show 140# at dash gauge for rear and between 105-110# on gauge for front. Both tanks test at 120#. WTH. How do I get accurate or close to accurate readings at dash.
I believe on your model year coach the dash air pressure gauges are electronic. As you already know, there is a pressure transducer on each tank. What you may not have discovered is the magic box that translates the signal from the pressure transducers, and sends the info to your dash gauges. Your problem
may be located in the magic box. Some of the magic has leaked out. :headwall:
See thread linked below for more bad news:
02 U320 Air gauge stopped working (https://www.foreforums.com/index.php?topic=37921.msg366674#msg366674)
My front and rear gauges consistently have a delta of around 20psi too. I assume it's the magic box chuck mentioned. Direct-read gauges are somewhere on my to-do list but I have forgotten where.