OH 1418 Dash electrics

[Kappy]

Here I go again, once again not sure if this belongs here.

Recently I discovered the dash instrument light had ceased working and my park brake warning not working so set about a discovering mission.

Park brake light discovered plug had wriggled loose, solved

Checked fuses, old ceramic types ( is there a substitute for these?) found some blown ones.

Anyway replace all bulbs of instrument panel and all good again, except for instrument lights on right dash side.
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All sections of dash seems to have different bulb, this whats on right section.
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I have tested the power at the end and seem to have power when headlights are illuminated and fuel and oil pressure gauges respond when ignition is turned on. No dash lights.
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http://i1201.photobucket.com/albums/bb3 ... pystlx.jpg
Also notice Air pressure warning light now non responsive even with air up.

The hand brake is currently detach from dash, wonder if that part needs grounding.
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Not arrow, this line I feel is air exhaust however connection is poor, anyone direct me to where I may be able to obtain a new one, please bare in mind I 2-3 hours from the city.

[Busman]

Bad ground, guaranteed

[Kappy]

Thanks,
As its not my forte care to enlighten me,please.

Any idea where to start, if bad ground how is it that parts of that section of the instrument panel work and other parts don't.

Confused??

[Busman]

Ground is the negative leg of the circuit. You are dealing with DC or direct current which in a simple explanation means a circle. Your power is coming from the positive side of the battery and goes through your device and then to complete the circuit must return to the battery. When you have power to something that should work (check with DMM) run a wire direct from the negative terminal and touch the negative part of the device. If a globe for instance that would be the outer silver part, the positive should be the small tit in the middle of the bottom.
Always assuming it is negative ground of course, 98% chance it is.

[Kappy]

Thanks busman,

I do understand the basics of pos and neg.

I've testest all the bulbs and they are working and done a basic test on the plug coming into the instrument, the issue is which pin is what.

[Busman]

Then use your DMM to tell you which pin is what, simples as that annoying meerkat says.
Once you find continuity write the wires down one by one as soon as you get a signal, just make sure that the signal is only on one wire.

[Kappy]

Really need some guidance please.

I have tested power at the plug and it appears to be what may be normal??

Fell the issue is the particular instrument, decide to refit, observed Fuel, temp and oil pressure gauge behaving abnormal.

Fuel showing full when bearly 1/4, Temp gauge indicating over 100C when not even close and oil pressure off the dial and no dash lights.
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Who would be the best test to test this section.

Or where would I start looking to replace it.

[BruceS]

Those 3 gauges showing "off the scale" indicate no earth. (or to be exact... circuit not completed)
I'm trying to remember but age happens you know?
Something tells me that on the Benz truck I had that the Earth fed through the gauges & then the senders back to pos.
Most vehicles is the other way around.
Pos through the gauges & THEN to the senders.
Once again a multi meter will help you.
Go to the easiest sender you can get to. Fuel tank sender?
Are there 2 wires or only one? If one, take it off & measure wire to earth on chassis. (scratch paint off)
What happens to the gauge if you touch that wire onto chassis? 2a fuse in circuit a good idea! Zero on gauge?

[Kappy]

Hi, Been a while,have some positive news.

Finally found a sparky than knows a bit about buses.

Checked some grounding and discovered lacking, all cleaned and two more added.

The suspect gauge was removed and dismantled to discover 4 lines within were cooked. See pic

20190225_093709.jpg

Once repaired and the gauge/panel returned with its own earth, everything working again, however with a twist.

Audible buzzer deemed U/S and was replaced.

Now I have audible alarm, that's seems linked to oil pressure, that desists when pressure reaches approx 3 bar, then goes off the dial.

Sparky can't offer explanation for the this.

During air build up oil pressure remains off the scale.

https://youtu.be/EK2HIWIykmw

While driving the pressure remains max, then on stopping the oil pressure drops to minimum and audible alarm sounds , till accelerating and all silent again, till next stop.

DO I have the wrong sender, if so can one of you knowledgeable guys suggest a correct sender.

Next job on hand is to look into the vehicle springs, I have a slight lean on the left side, seems to have got worse.
Not a lot has changed inside. Getting so called expert to have a gander on Tuesday and see whether I need to sell a kidney.

Anyone have any knowledge of any other solution to level ride without doing springs.

Lets keep the sarcasm to a minimum, please

[BruceS]

Probably need to find out exactly what the buzzer warns for before you go much further.
From memory on a similar vintage Benz truck the buzzer was on for ..
1. low air pressure.
2. high water temp.
3. low oil pressure.
Buses may be different though.
The electrics on Benz vehicle are almost impossible to understand/follow.
If you can find one of the 'old time' Benz mechanics he could probably sort it out. (Hank at Benz Trucks in Adel used to be worth a truck load of Gold. Probably not there now?)
eg. Don't use any coolant as such .... one table spoon of white oil is all it needs. Any more will rot your hoses out.

As for the lean?
Are there anti-sway bars on front & rear axles? Might be able to install a block in the mounting to throw more pressure on left hand side? If they are on it they are at least an inch in dia. Mine had adjustment on the hangers. Can you get a photo of them if they are on it?

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