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Mercedes O305 Questions

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Mercedes O305 Questions

Postby 404wanderer » Wed Aug 20, 2014 11:01 pm

Hi all,

I've just acquired an ex Trans Adelaide Mercedes O305 and have some very newbie questions. Apologies in advance for the stupidity but I have an MR licence and am used to driving small manual trucks rather than buses.

So in no particular order -

1 - the airbags aren't inflating. There is a hissing noise like air escaping from underneath the bus but I can't seem to find where from. Is there a drain valve I need to close? Any other suggestions? Both air brake circuits seem ok but the airbag warning lights are on.

2 - since I pressed the alarm foot switch by mistake my bus now says emergency as the destination. How do I change it? The selector above the drivers seat doesn't seem to power up.

3 - ok, so the questions may be getting stupider. The dash has selectors for gears - 1,2,3,N,R. Now, how is the bus normally driven. Is it manually changed on the dash for each fear change or is that just the highest gear? I.e do I just put it in 3 and drive or do I need to keep using the buttons to change up and down

4 - there is a retarder switch on the dashboard. When do I use it?

5 - what is the procedure for long descents and ascents?

6 - when I'm parking up for a while do I need to do anything special or just switch off?

7 - thanks!
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Re: Mercedes O305 Questions

Postby Willie » Thu Aug 21, 2014 9:22 am

Desto sign, with power on, select Dest A, enter a code, like 1, enter and it will change the sign.

Most retarder switches are disconnected.

Drive in highest gear, can select a lower gear for a long descent but they can be quite temperamental.

With the airbags not inflating, there is two air gauges on the dash, 8 bar is desired for both front and rear brake, what do they build up to? How long are you allowing for the air to build up?

From memory there is no master battery switch, just key out, though check around the battery box, I'm open to correction. Do you know it's old fleet number?
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Re: Mercedes O305 Questions

Postby Guy_Arab » Thu Aug 21, 2014 11:44 am

404wanderer wrote:Hi all,

I've just acquired an ex Trans Adelaide Mercedes O305 and have some very newbie questions. Apologies in advance for the stupidity but I have an MR licence and am used to driving small manual trucks rather than buses.

So in no particular order -

1 - the airbags aren't inflating. There is a hissing noise like air escaping from underneath the bus but I can't seem to find where from. Is there a drain valve I need to close? Any other suggestions? Both air brake circuits seem ok but the airbag warning lights are on.

2 - since I pressed the alarm foot switch by mistake my bus now says emergency as the destination. How do I change it? The selector above the drivers seat doesn't seem to power up.

3 - ok, so the questions may be getting stupider. The dash has selectors for gears - 1,2,3,N,R. Now, how is the bus normally driven. Is it manually changed on the dash for each fear change or is that just the highest gear? I.e do I just put it in 3 and drive or do I need to keep using the buttons to change up and down

4 - there is a retarder switch on the dashboard. When do I use it?

5 - what is the procedure for long descents and ascents?

6 - when I'm parking up for a while do I need to do anything special or just switch off?

7 - thanks!


I sent you some data that may help private email
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Re: Mercedes O305 Questions

Postby 404wanderer » Wed Aug 27, 2014 12:44 pm

Thanks Guy and others,

In summary, I'm replacing the airbags anyway but I've been operating the parking / auxiliary brake incorrectly. I'll have a look at that and see if that stops the air escaping.

The emergency sign I haven't sorted as the destination selection panel is dead. I'm going to try and see where it gets its power from to see if I can resurrect it.

Sorted how I use the gear selector!
Not sure why the retarder would be disconnected but I need to have a play to see if it is.
Parking brake operates with a twist to drain water form air tanks.

One other thing I haven't been able to find out is how the engine start and engine stop buttons work. They're not mentioned in the manuals so may be a fleet addition. The stop button doesn't actually work at present and the only way I can stop the engine is to pull up the accelerator pedal with my boot, which eventually stops the engine. Does anybody have and idea how the engine stop buttons normally work? What do they do to the engine; is it air or fuel they cut off, or something else?

Thank you all for your patience with a newbie :-)
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Re: Mercedes O305 Questions

Postby Willie » Thu Aug 28, 2014 1:05 pm

With the stop button, your generally to have 6-8 bar in each tank for it operate.
Pulling up the accelerator pedal but be careful not to wear it out!

Does the Desto have a flick switch on it at all?
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Re: Mercedes O305 Questions

Postby 404wanderer » Thu Aug 28, 2014 8:33 pm

Ah, ok, I was wondering how it operates.

What's a flick switch?
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Re: Mercedes O305 Questions

Postby 404wanderer » Thu Aug 28, 2014 10:22 pm

Is there a better way of stopping the engine if the stop button doesn't work? I had both brake circuits up to pressure but the bags weren't inflating. That could be why there wasn't pressure to the stop circuit.
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Re: Mercedes O305 Questions

Postby 404wanderer » Mon Sep 01, 2014 10:40 am

Just found the large handle in the engine marked "Engine Stop". Once I'd cleaned the dirt off the label that is :-)
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Re: Mercedes O305 Questions

Postby R-C » Wed Sep 03, 2014 11:43 am

On the right hand side of the accelerator on the floor is there a black button?
Press that to see if it turns bus off
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Re: Mercedes O305 Questions

Postby boronia » Wed Sep 03, 2014 12:15 pm

I'm not familiar with this model Merc, but usually the STOP button operates a solenoid on the fuel pump
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Re: Mercedes O305 Questions

Postby Andrew » Thu Sep 04, 2014 11:21 am

O305s I have driven you have to lift the accelerator pedal up towards you to shut the engine down - I assumed it was lifting something by cable in the air intake of the engine to starve it and thus cause a shutdown.
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Re: Mercedes O305 Questions

Postby boronia » Thu Sep 04, 2014 1:25 pm

Usually lifting the accel pedal simply pulls the injector pump rack back beyond the idle position, shutting off fuel to the engine. THis is how it worked on the older AECs

The third method, simply turning off with "ignition" key, requires the pump solenoid to be powered to open the pump. One downside of this is you can't clutch start the vehicle if it has a flat battery.
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Re: Mercedes O305 Questions

Postby DiAmOnD T » Sat Sep 06, 2014 10:55 pm

If your air bags don't inflate and the engine stop is not working - Do the doors work??
If they don't then you are not getting an air supply into your auxiliary tank for these items, which would suggest your 4 way protection valve is sticking/faulty.

If you can get underneath the bus you should find a couple of long air tanks side by side, one will have a square valve mounted off it, which in a way looks like the bottom of an egg carton. If you find it give it a belt with a hammer and try building air again to see what happens
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Re: Mercedes O305 Questions

Postby Drewwarner » Sun Jan 15, 2017 6:20 pm

Guy_Arab wrote:
404wanderer wrote:Hi all,

I've just acquired an ex Trans Adelaide Mercedes O305 and have some very newbie questions. Apologies in advance for the stupidity but I have an MR licence and am used to driving small manual trucks rather than buses.

So in no particular order -

1 - the airbags aren't inflating. There is a hissing noise like air escaping from underneath the bus but I can't seem to find where from. Is there a drain valve I need to close? Any other suggestions? Both air brake circuits seem ok but the airbag warning lights are on.

2 - since I pressed the alarm foot switch by mistake my bus now says emergency as the destination. How do I change it? The selector above the drivers seat doesn't seem to power up.

3 - ok, so the questions may be getting stupider. The dash has selectors for gears - 1,2,3,N,R. Now, how is the bus normally driven. Is it manually changed on the dash for each fear change or is that just the highest gear? I.e do I just put it in 3 and drive or do I need to keep using the buttons to change up and down

4 - there is a retarder switch on the dashboard. When do I use it?

5 - what is the procedure for long descents and ascents?

6 - when I'm parking up for a while do I need to do anything special or just switch off?

7 - thanks!


I sent you some data that may help private email
Guy Arab


Hey Guy,

Do you still have a manual for a MB O305 for sale? I am in need of one.

Thanks!

Drew
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Re: Mercedes O305 Questions

Postby DRIVEN1 » Tue Jul 30, 2019 1:07 pm

Hi All,

I just failed an annual inspection for my recently purchased 0305.
One of the things I have told to rectify is the oil light coming on with the other warning lights after the "battery connect" button is pushed, prior to starting the engine.
I have replaced the bulb for the oil light but still no luck. Is this a common fault? Any help would be appreciated.

Kind Regards

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