Possible faulty central locking relays?

[walty666]

Hi,
The central locking has died on the van. Was intermittent for a while but now completely dead. My aftermarket remote locking still operates the drivers door and is a simple actuator attached to the factory plunger in the drivers door. I've not touched the factory C/L system. Checked both fuse 1 and 4 and both are fine. Checked the connector in the door panel and there's a low voltage pulsed signal when the plunger is operated.
I haven't checked the driver side loom from the wing to the door because the low voltage pulsed signal is also being seen at the relay unit behind the glove box. There's a constant 12v in to the relays, a 0v earth, but no 12v pulsed outputs when the driver lock is operated. Does this signify a faulty relay unit? I thought it was more common to see a constant 12v output when the relays fail? Both the passenger, sliding and tailgate doors have stopped locking so it's pointing to a common fault under the dash...

[g8dhe]

The signal from the drivers side is a changeover switch K2-01 below;

So you need to check that the +12v from the door switches from the Yellow/Red to the White/Black going into the module and back. It might be that only one of the two signals is getting thru the loom at the drivers door....

[jaylee]

I thought it was more common to see a constant 12v output when the relays fail?

In my experience yes, when testing with a meter off the sliding door contact for the CL.... This was with another members Bongo who's loom i was repairing anyway (Window.) & my advice was to pull the fuse or remove the relay so as not to cause damage (if any done already.?) to the locking solenoid/s...?!!!

A new/used CL relay cured this with the doors...


I would agree with Geoff... Look at the door loom first before possibly needlessly splashing on a relay.... Go on, you know you want to....!?

[walty666]

I'll have to check the control signals from the driver's door into the C/L unit again then. I definitely wasn't getting 12V because I had to turn the multimeter resolution down to 200mV or 2000mV, and was only then getting a steady 2.0 signal or 0.0 dependent on the pin and whether the driver's door was locked or unlocked. I assumed at the time that the control signal into the relays would be much lower than 12V, and that the relays then pulsed a 12V signal to the other doors.
Not getting anything at either of the sliding door contacts (assuming they're the non-sprung ones?)
Couldn't even work out how to unclip the cable loom clip around the door hinge yesterday! Checking that' going to be fun...

[g8dhe]

If you were getting a couple of volts then that probably does indicate a broken wire, the voltage you were seeing was coming from the unit and was simply the input to the pulse generator circuit in the module, most logic gate inputs will float at around a couple of volts when disconnected.

[walty666]

Oh, OK then. Definitely didn't appear to be getting anywhere near 12V. There's a connector in the driver door panel as well which I tested. I'm assuming that the blue/red wire should be feeding a constant 12V to the door switch, and then I should be getting a pulsed 12V signal in either the yellow/red or white/black when I lock/unlock?

[g8dhe]

Yes you will get 12volts from one of the wires all the time, which changes to the other when the switch is operated, not sure if the switch is only operated momentarily i.e. pulsed or is in one position when closed and the other when open, I think the latter is more likely. The signal is turned into a pulse within the module and the output is a pulse of 12 volts in one direction or the other going onto all the other door lock drives.

Yes just checked the other diagrams the contents of the module are below;

The switch itself is not pulsed, the 12 volts simply powers the two monostable circuits inside the module into operating one of the two relays in order to create a 12 volt pulse to power the other door lock drives.

[walty666]

Just got round to checking again. It does appear that I'm gettin the interchangeable 12v signal into the relay unit behind the glove box. I'm also getting the constant 12v feed as well. However, I'm not getting anything on either output to the slaves from the relay unit. As such I can only conclude that it's the relays that have gone and not the door loom...

[g8dhe]

You will only see an Earth on the two output leads (R and R/G) most of the time with the occasional pulse of 12 volts for about 0.5-1 seconds when the input signal changes over.

[walty666]

Would this 12v output pulse be too quick for a multimeter to pick up?

[g8dhe]

Its possible, the Digital meters are not the best for spotting shortish pulses as they only sample the voltage at preset intervals, if you have, or make up, a simple LED or bulb tester then you ought to get a better indication. A digital meter might just show a small increase in voltage nothing like 12 volts during pulses it just depends when the sample is taken, and you have no control of this, unless you have a Peak detection option, in which case turn it on and operate the lock lots of times then there is a much better chance of a sample hitting the pulse.

Taking another tack disconnect the module, and apply an earth to the R/G wire and then use a short wire to generate your own pulse on the R wire, reverse the connections as well as once the door locks are operated then they use a diode in the slaves to disconnect themselves until the opposite pulse arrives.

[walty666]

OK. Tested the slave locks by simulating a 12v pulse as outlined above and they all still lock. So, if I'm getting the 12v constant power in, the 12v control signal from the driver's door in, and all the other locks are functioning on a simulated 12v pulse out to the red/red yellow wires respectively, then it must be the relay unit right? Have contact bongobits4u2012 and awaiting a return call...
Thanks for all your help btw!
Ross

[g8dhe]

Certainly sounds like it, you've eliminated everything else now.