Help needed with Bus door control circuit.

I am rebuilding the passenger door mechanism on a Mercedes 609D bus.
I have rebuilt the door rams and motor, which work fine. If directly hook up the 24v motor then it turns one way and the doors open. If I then switch the polarity, then the motor turns the other way and the doors close.

There is a micro switch on the door rams that opens when the door is fully closed, and another which opens when the door is fully open. The micro switches are not currently connected to anything.

There are various push buttons inside and outside the bus for opening and closing the door. The buttons are push to make contact, and break contact as soon as you let go of them. I am presuming that when an open button is pushed and released that the door should open completely without having to hold the button down the whole time. I'm assuming the same for the close buttons too.

The original circuit board was still in place. Partly wired in.

It is a FKI Peters Bradbury - 065-302-A4 Issue 2.

I'be tried to understand how it works and how to wire it back in, but I'm pretty inexperienced and despite spending some time scratching my head over it, I have yet to work out what needs doing.

This is what the circuit looks like








Here is how it was wired in before I removed it to investigate how it works
(There were no wires doing to right hand connection block, not shown)



Here is what those wires did. Although I am not 100% on 10 and 11



Here is my strange diagram of what connects to what on the circuit, which I made by poking around with a continuity tester.



Any help would be massively appreciated!

Thanks for your time.

Jason

11 is the 24V feed
10 is the ground
1a and 1b is the closed limit switch ( ie the one that opens when the door is closed )
2a and 2b is the open limit switch ( ie the one than opens when the door is open )
8 and 9 is the door light switch ( like on a car door, the door opens, the light comes on ( resumably there's one over the door inside? )

I'm not entirely sure at this point where the motor connects to.. bear with me

ok i think the motor connects between 3a and 4a.

you need to get 24v to number 7, which I think might be from the ignition, or from a keyswitch on the outside panel ( to stop you opening the doors without the key.. )

Thank you very much I'll be giving it a go in the morning, and will report back. I really appreciate your time and help.

ColJack said:

you need to get 24v to number 7, which I think might be from the ignition, or from a keyswitch on the outside panel ( to stop you opening the doors without the key.. )

Click to expand...

Is it essential to the circuit that I get power to number 7?

Additionally I forgot to mentioned that I traced back the +24v volt line, that goes into number 11, beyond the door reset switch on the dash and found that it is feeds from a relay that turns the power on and off by the ignition switch.

Does this mean that I can forget about getting power to number 7?

nope, still need power to number 7.. unless you missed a line on your drawing..

is there a keyswitch on the outside controls?

Are you sure about the +24v to 7?

Won't this effectively short across the closed limit switch, forcing RL3 to be picked all the time?

ColJack said:

nope, still need power to number 7.. unless you missed a line on your drawing..

is there a keyswitch on the outside controls?

Click to expand...

My diagram isn't the best, but I've just doubled checked number 7, and I haven't missed anything out. Maybe it's because my diagram isn't very clear.

Number 7 is linked to 1B and the lower right terminal on RL3.

There definitely isn't a keyswitch outside of the bus, perhaps because, unusually for a bus, there is a drivers door.

Referring to the original wiring photo, fourth image down, I'm inclined to think that number 7 is not used in this case. All the wires present are wrapped and cabled tied which makes me think that if there was another cable then it would have been tied and wrapped with the rest, and if it was removed then perhaps there would be a sign.

Of course that is based on nothing more than looking and a gut feeling, rather than any knowledge of how the circuit works!

Although I do now have a better understand thanks to your help.

deleted

tomathy said:

Are you sure about the +24v to 7?

Click to expand...

no i'm not.. ( come on it was late on a sunday night.. )

Won't this effectively short across the closed limit switch, forcing RL3 to be picked all the time?

Click to expand...

yes it will, my bad..

don't know what I was thinking at that point..

so the operation as far as I see it ( and someone trace this out mentally to check it for me please ) is as follows..

the door is shut.
the close limit (C/L from now on ) switch is open so RL3 is off and cannot operate.
pressing andy close button does nothing since it goes through the NO contact of RL3 to the coil of RL2.

the open limit ( O/L from now on ) switch is closed. pressing the open button puts 24v on numbers 2, 4, 6 and 2A

that 24v goes through the O/L switch ( 2A to 2B ) and energises RL1 which latches itself with the middle set of contacts and puts the 24V from 2 onto 3A ( to the motor )
at the same time it removes the 0V from one side of RL2's coil so pressing the close button at the same time does nothing.. ( since opening the door causes the C/L switch to close and energise relay RL3. )

when the door reaches it's fully open position, it opens the O/L switch, removing 24V from nubmer 2B and dropping relay RL1 out, thus unlatching it and removing the 24V from 2, 4, 6 and 2A.

the door is open.

the O/L switch is open so pressing the open buttons do nothing
the C/L switch is closed so RL3 is energised and the interior lights are on and pressing the close button puts 24V on number 3, through the NO contact on RL3 ( which at this time is closed ) and onto the coil of RL2, energising it
this latches RL2 on by getting 24V from 1, through the middle NC terminal of RL1 to the middle NO terminal of RL2 and onto terminal 3 ( I'm not entirely certain but pushing the open button while the door is closing should overide it to open again.. ).
this also puts 24V onto 4A ( to the motor ) via the right hand NO terminals of RL2.

Result! A fully working set of doors, Hurray!

I'm delighted. Thank you for the detail explanation. It all makes sense now.

Massive thanks to you ColJack, and to tomathy too. I'm really very happy.

DIYnot delivers once again.

Cheers!

I owe you one.

what about all those other forums you posted to.. did you get a helpfull reply?

ColJack said:

what about all those other forums you posted to.. did you get a helpfull reply?

Click to expand...

Ah the other forums I have just concluded my threads there by referring to this thread.

This is the only forum that provided me with a super helpful solution.

Thanks once again!

ok, it's quick and it's messy but this is the circuit diagram as far as I can tell..

the capacitor and resistor across the motor is some kind of time delay I think, either delaying it on or off...


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