window rollup module basics

Maybe it's because I only work on older cars (that don't have factory window relays?), and definitely it's to do with the crappy schematics that come with every window rollup module I have been able to research...but I don't get how *any* of these could actually do what they're supposed to do - that is, without additional external relays and a lot of futzing that I'd rather not have to do to mount & wire them. To me, the point of getting one of these modules, as a companion to a remote-locking receiver, is precisely because I want it to be able to - independently - roll up the windows, after some simple cut/splice connections between my window-switches and motors. Window motors that I know are simple DC items that need both a ground and hot lead to move, and mine (at least) have no relay isolation (I assume some do, but my question still stands) - they're directly controlled by up/down switches. When a window-switch is in relaxed "normal" position, there's no ground or hot connection to the motor. So when a window module puts out a 12V signal, and it's even shown wired interrupting the switch lead to the motor, well...it leaves me baffled as to how that motor is going to move, since yeah, it's getting that 12V source, but it's not getting a ground.

Am I missing something, or can any of these work without external relays to interface them?

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Dave

Typically, but not all, window motors rest at ground through the switch. If yours do not, then you will need additional relays. The instructions (destructions) included should show this. If not, let us know.

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the12volt • Support the12volt.com

Scanned image of connection diagram is uploaded - my penciled notes are from bench-testing to verify how connection options worked. So I have to add relays to ground my motors, then? That's...annoying. I bought this model from a domestic seller & paid more via Amazon specifically because I thought they'd be responsive to my questions along these lines, if/when the instructions were no good - nope. Now I think I'd have been better off ordering directly from the PRC.

Couple weeks back, I did verify no ground exists at motors normally. Rocker switches just swap polarity to motors, as I'd assumed all would do, with center position being off & ungrounded.

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Dave

what is the vehicle you are trying to use this on?

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yuk
quiet rural missouri, near KC.
If your system moves you physically and not emotionally, you have wasted your money.

If your motors are open circuit at rest, you have a system used by say 1% of vehicles.
Forgetting low current switching and BCM control on the newest vehicles, about 95% use NEG at rest, 4%, older Mercedes, VW use POS at rest so please stop moaning maybe you're just unlucky
As itsyuk says make model and year?

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Test before boxing up.

Hmmm - even I'm confused, at least without knowing the target wiring.

I wired my windows (retrofitted to a 1965 vehicle) using relays - ie, 2 SPDT per motor.
I wired rest at GND for both sides. (That is the obvious choice for safety reasons.)


In that AU-93-4 wiring diagram, I don't understand how it can say merely xxx Switch side or - more so - xxx Motor side without specifying the "up" direction - that's unless it's a dual motor system or the control uses f.ex 0V for off, 12V for up, 6V for down (but who'd so that?), OR if its a comms signal (CAN etc).

In my case the above unit would have to be after my relays - not between the switch & relays - to use its current sensing shut-off.


But in relation to the OP's problem, tho motors can be totally floating (open circuit) when off, that is the choice of the manufacturer etc. Usually it's easier leaving the connected when off (as in the case using 2 SPDT relays), but in others they'd be open (eg, if using 4 SPST relays instead of 2 SPDT).
For switches, longer and overlapping contacts/tracks are usually more reliable - ie, less contact to no-contact transitions - hence the GND at rest etc.

Finally getting back into this, months later. (Is there a rollup module that would work as-is, ex-factory, without all this futzing around with external relays?)

So:
1) I didn't have this thread set to notify me...oops...
2) Vehicle is a 1983 Mercedes-Benz 300SD
3) yeah, I hadn't squinted hard enough at my vehicle schematic to discover that the window switches rest the motor leads at +12V (something I think Howie was covering above), and those leads are SPLICED and dead when the ignition key is out...
4) ...so I guess I wasted a lot of time and created needless drama in my life by wiring up a 4PST relay, expecting it to ground what I'd /thought/ was simply the neg side of each motor, but which turns out to be a spliced set of leads to both sides of each motor - so when activated, the module was trying to send +12V to that same (now grounded and spliced) pair of leads.

Yeah, so no wonder a fuse blew, once I plugged the switches back in to test.

I now think that basically, my approach was polarity-reversed, with a twist, where the 4PST relay can't be used.

I did learn that the module closes each window in a sequence, presumably to minimize current through it.

So am I thinking right this time? I think my "simplest" fix would have to be to:
1) Use four /individual/ SPST relays, each inserted into respective motor /ground/ leads, as follows:
a) the common connected to motor (-),
b) the NC side to window control switch, and
c) each NO contact goes to ground (as does one side of the coil, while I am at it)
Thus, activate a relay, and it will open that pair of spliced motor leads, and give that motor a (-).

2) Splice the module's "motor" leads (4ea) to
a) each window motor's (+) side
b) each corresponding relay coil.

3) snip off and insulate the module's four "window switch" leads, since they can't be used for anything.

Am I overlooking anything (again)? It occurred to me that with the terrible documentation and quaint English supplied with this module, it's even possible that it might be internally-switchable so as to provide (-) to each window instead of (+), which would allow me to eliminate ALL relays.

--Pants


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Dave

Shortly after posting, I found that a distributor of these modules came up with a much more efficient mod to fix this - and it uses just one SPST relay. It turns my brute-force fix inside out, by snipping the normal 12V supply to switches, so that they only operate "normally" when accessory-power closes their contacts - and otherwise they rest at ground, thus allowing the module to operate in "generic" mode.

Why didn't I think of that? (and...why didn't the OEM documentation come with something like this?)


Other conditions are also shown in the augmented data-sheet at https://www.connect2car.com/Manuals/Au_93_4_window_module.pdf

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Dave

Well I did say 4% and your luck 80s Mercedes were that type, I believe the DEI 530t can do it without an external relay.
Plan B turn the feeds and grounds around the other way at the switches.
There was also an Italian Alarm company called Scorpion, they supplied Mercedes with dealer fit alarms (in England) and of course they had a custom window closer. But that was 30 years ago.
It's arcane knowledge these days, nearly all Euro and Japanese have one shot closing and all the motor wires are NEG at rest.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

It just occurred to me that if the power supply sits at ground with the ignition off and you only use the window closer with ignition off, you won't need a relay since all the wires will be at ground.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

howie ll wrote:

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It just occurred to me that if the power supply sits at ground with the ignition off and you only use the window closer with ignition off, you won't need a relay since all the wires will be at ground.

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Odds are the power wire doesn't sit at ground when the ignition switch is off. It just shows a path to ground through other stuff that sit on the same circuit.

'83 Mercedes, come on now it's about time to move into the modern era, after 31 years, and buy a new car with window roll-up and other amenities built-in.

catback wrote:

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'83 Mercedes, come on now it's about time to move into the modern era, after 31 years, and buy a new car with window roll-up and other amenities built-in.

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hmm...I'm awaiting Windows 9?

Actually the diesel 300SDs and similar models are legendary and sought-after for their longevity, eg 500K miles and much more with reasonable maintenance - to say nothing of their tolerance for running on alternative fuels with little or no modification (waste vegoil, for example). I do wish I could buy a 2014-anything that could do the same, especially something less than 17' long.

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Dave

Catback's, bet it does sit on solid ground, test and if so worth a try but I don't really care I must have 100 relays lying around.
Pants, your absolutely right I've worked on two recently, both owners have had them from new and commented on NO COST running.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Thank you Howard.
"It just shows a path to ground through other stuff that sit on the same circuit. " means it is at ground.
How grounded? - add up all the parallel resistances, or try grounding a 3W or 10W or 55W or 100W bulb thru turned off IGN.

In my case, at least, no, there's no chance ground available by just keying off - though I'd love to find an even easier way around this, so I'm attaching the musty old schematic and maybe someone will see something I don't/can't.

I think Catback might have been referring to the "impression of a ground" that you'd get from an ohmmeter reading through, say, a filament of an indicator lamp that happens to tie into that hot-lead - and thence to ground. But try to USE that lead as a ground with a low-impedance device like a window-motor, and most likely all the voltage drop will be across the filament.

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Dave

Have you tested that power supply (supplies) to the window switches (can't read your too small diagram), I'm sure one is BLACK / YELLOW with a DMM with the ignition off?
In other words both motor wires to each motor should rest at ground.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

With old vehicles there was a reasonable chance of a 2-4 Ohm GND thru the IgCoil alone.
But as Howard suggested - TEST. The number of times we have used phantom- or pseudo-grounds like this for anything from LEDs buzzers & relay coils to lamps of reasonable current.
And if it can actuate a relay coil...