Tag Axle won't raise

[Topman]

I went under the coach today to check the operation of the tag switch.
Key in on position, tag switch activated, automatic exhaust of air for tag bags but the brake cans which lift the tag don't move.

Only the red needle on the air gauge goes down.

After the initial air exhaust, I can hear air escaping from the rear tank to a leak somewhere. I can't identify the valve which exhausts the air from the tag bags.
As long as the tag switch is on, the air is leaking. Switch off and system stays up for several weeks.

Is it possible the MAC valve in the engine compartment is not working in order to send air to the brake cans for lifting? How to test?

The gauge seems to work okay for the pressure setting.

The 6-pack on the left operates the tag bags.
The 6-pack on the right operates the drive axle bags and height valves.


Any thoughts?
Thanks, Iver.

I have a couple of pix of the area.

[Topman]

Okay, I think I have it figured out. When I turn on the switch for the tag axle, the tag bags dump and the MAC valve is opened to supply air to the lift cans.
Then I get a constant leak. So I disconnected the MAC valve and the leaking stopped. So I need to see where the leak or leaks are in the lift can circuit.

I will check the diaphragms in the lift cans to see if they are the reason.

What is the best way to cage those cans? I can use the lift arms to pull out the rods and compress the springs or??

I pulled one tag wheel off and disconnected the lift can and noticed the arm is really stiff to move so I lubricated it and now it moves without too much effort. Probably because I really never used the tag lift and I doubt the previous owner did as well.

So anyway, once I rebuild the cans, I should have everything back to normal. (hopefully)
Iver.

[Topman]

All fixed.... sort of!
Changed out both diaphragms in the lift cans.
Both lift arms needed lubrication. Very stiff/seized.

Now tag axle lifts when the switch is on. The only problem now is the MAC valve is working on and off. I had to tap on the valve to make the exhaust stop and tap on it again to get it to open. So I guess a replacement is in order.
Hopefully then, problem solved........
Iver.