Gauges

[Digcolnagos]

The air pressure gauge for the front brake shows full pressure when the 1998 Blue Bird TC2000 is shut down; the oil pressure, temperature and RPM gauges also are elevated when bus isn't running, see photos. Bus drives fine. Should I be concerned? Thanks.

[magnakansas]

the big deal is that your gauges read correctly when key is "ON" position.

william

[Booyah45828]

The only gauge that still "reads" with the key off is the air pressure gauges, as they are pure mechanical and indifferent to key position. The rest will be off and the needle will rest wherever they decide to rest. It's supposed to rest at 0, but residual magnetism can place it wherever.

Once the key is on, they should all read normally.

Only thing I'd be alarmed with is your rear tank being at 0. But if it's sat for awhile, maybe the front tank might simply hold air better, so it might not be a problem.

[Digcolnagos]

Originally Posted by Booyah45828

The only gauge that still "reads" with the key off is the air pressure gauges, as they are pure mechanical and indifferent to key position. The rest will be off and the needle will rest wherever they decide to rest. It's supposed to rest at 0, but residual magnetism can place it wherever.

Once the key is on, they should all read normally.

Only thing I'd be alarmed with is your rear tank being at 0. But if it's sat for awhile, maybe the front tank might simply hold air better, so it might not be a problem.

Thanks. The rear goes to level of front a minute or so after ignition and all is fine. Bus sat somewhat, I think, before I bought it. Not sure how much exercise it got.

[Iceni John]

Electronic gauges with needles moved by stepper motors will do that. When power is cut to them, the needle remains where it was last told to go by the stepper motor. I have several gauges that do just that. Mechanical gauges, such as pressure gauges with Bourdon tubes, will naturally return to zero when there is no more pressure; the tube acts like a return spring. If you have an electronic gauge and the needle never returns to zero when power is reapplied, the gauge is dying and will need to be replaced.

John

[Booyah45828]

Originally Posted by Digcolnagos

Thanks. The rear goes to level of front a minute or so after ignition and all is fine. Bus sat somewhat, I think, before I bought it. Not sure how much exercise it got.

I'm not worried about how long it sat before you bought it. But how long that needle takes to go to 0. It should fall less then 2 psi/minute, so if you had a full tank and it went to 0 psi 5 minutes after shut-off, you've failed the test and have a leak somewhere.

Tanks can leak air slowly over time, so long as it isn't more then 2psi/minute. So if the bus sat overnight and this is how you found it the next morning, it might be nothing. It's just odd that one tank leaks empty and the other holds 100+ psi. Typically they will both leak an equal amount overnight.

[cadillackid]

Originally Posted by Booyah45828

I'm not worried about how long it sat before you bought it. But how long that needle takes to go to 0. It should fall less then 2 psi/minute, so if you had a full tank and it went to 0 psi 5 minutes after shut-off, you've failed the test and have a leak somewhere.

Tanks can leak air slowly over time, so long as it isn't more then 2psi/minute. So if the bus sat overnight and this is how you found it the next morning, it might be nothing. It's just odd that one tank leaks empty and the other holds 100+ psi. Typically they will both leak an equal amount overnight.

I had this happen on my DEV bus when the rear air springs had a leak... it drained out the secondary tank down to the protector valve pressure of 60-65 but the other needle would be on 90-100 in the morning..