S124 central locking pump types

[jonsheaf]

I've recently aquired a nice 300D multivalve estate W124.
When I first got it I had some shenanigans involving the doors locking themselves when I tried to unlock the boot (IR key not working these days).
Originally I put it down to me not turning the boot key enough to the left and possibly the boot lock knob being up or down fully.
Fast forward a couple of weeks, and....
It's comeback!! Good old OLD cars!!
So, I've checked the pump under the seat for it's part number.
I've got MB 124 800 21 48.

Now, looking through many other posts where I suddenly do not feel alone regarding this issue, I also found this snippet of info, although it's for a CE, which has got me thinking....


For W124CE
A1248002148 - no immobiliser, no ortho, no infrared
A2028000048 - immobiliser, no ortho, no infrared
A1248002848 - no immobiliser, ortho, infrared
A2028000148 - immobiliser, ortho, infrared (the daddy)

A1248001348 was replaced by A1248002148.

So according to the info my pump has no IR compatibility, (could this explain the IR key changing the led from red to green and vice versa, and a pump sound but no locks opening/closing???)- I mean someone could easily have fitted the wrong pump...?
Should I look out for a different pump(###1348) and try it? It could solve both issues!

 

[Dec]

A better solution might be to repair the vacuum pump… if possible.

When you unlock the car with the remote fob button, the Green LED should flash for a few seconds, hazards flash 1 time and the alarm should be disabled and the doors should unlock.
Does the vacuum pump run when you unlock the car, if so, how many seconds does it run?

Conversely

When you lock the car with the remote fob button, the Red LED should flash for a few seconds, hazards flash 3 time and the alarm should arm and the doors should lock.
Does the vacuum pump run when you lock the car, if so, how many seconds does it run?

Will all the doors lock/unlock if you only use the metal key blade in the door lock?

Dec

 

[jonsheaf]

The led does what you say yes, and the pump can be heard running for a similar amount of time as is heard when (actually) unlocking the doors using the key (about 5 seconds).
I have no metal blade key, but 3 IR remotes. 2 work well, and the other either has dead batteries or is a spare.

Following the crazy quick self relocking episode today, the pump could be heard doing the "diving hum" noise on and off for a bout 20 seconds whilst driving, that's why I thought for £25 I would just try swapping the pump?

 

[Dec]

Replacing the pump, as you suggest, would be the easiest solution alright, the pump that you have is probably the correct and original pump, it just seems to have poor/dirty electrical connections… if it is sometimes succeeding in actually locking/unlocking the doors?

Ideally, the pump should run for about 2 seconds when you lock or unlock.

Not sure about your car but some are set up to lock all doors automatically when the car reaches a speed of 10 miles per hour… is this when the “crazy quick self relocking episode” happens?

Dec

 

[jonsheaf]

Thanks for the help Dec,
Re the self locking , you know I really can only say I noticed it today, as was aware of the locking playing up. but it was as we pulled away from standstill yes! (It's a 1996 late one so could that hint at the self locking system being present?)
The pump has never yet locked/unlocked the doors on the remote, but only on the key (boot/pass door), but does the right thing re l.e.d green/red sequences.
I should probably mention that the car has a small push switch mounted near the steering column that I nor the previous owner know about. Now I don't know if it's linked to this or if this is to do with the dealer fitted alarm but- the wiring right next to the pump has a thick yellow and a thick green wire spliced into the the loom, and a small resistor is showing through the not amazingly proffessional insulating tape where they splice in. these 2 wires head towards the front on the drivers side. !!??

 

[Dec]

Usually those cars didn’t have factory fitted alarms hence the dealer fitted alarms, the two wires spliced at the pump are likely going to the alarm, when you lock, you arm the alarm and disarm it when you unlock

Is the switch on the dash also a LED light?, this switch on the dash is possibly for disabling the two internal motion sensors and may? light up when the motion sensors are disabled.


Try the following;

-Lock yourself in the car so as the alarm is armed and remain motionless for about 30 seconds to allow the alarm to set itself up.
-Red LED should flash for a few seconds.
-Hazards should flash 3 times.
-After 30 seconds wave your arms about so as to trigger the motion sensors.
-The Red LED on the passenger side motion sensor should flash, triggering the alarm, the hazards should also flash for about 20? second and the alarm siren should sound?
-unlocking the car should disarm the alarm


To test if the switch is indeed for disabling the motion sensors, try the following;

-Remove key from ignition.
-Open door.
-Press the switch on dash once.
-Remain in the car and shut the door.
-Lock the car and remain motionless for about 30 seconds.
-Red LED should flash for a few seconds.
-Hazards should flash 2 times… instead of 3 times, because/if you have disabled the motion sensors with that mystery switch.
-After 30 seconds wave your arms about so as to trigger the motion sensors.
- If the switch is indeed for disabling the motion sensors then the motion sensors won’t be triggered by you waving your arms.
-Opening the door will now trigger the alarm.

Test your remote fob as below.

Dec

[YOUTUBE]zQhwvjw29NA[/YOUTUBE]

 

[jonsheaf]

Thanks.
I'll try the motion sensor disabling test tomorrow. I know the hazards part of the alarm work, yet the siren doesn't (it's still under the bonnet but is either disabled or dead).
The dash button has no led no just a button really. The motion sensors- the pass side one flashes in time with movement, the drivers side looks a bit damaged ( the red led is missing)

* with the "alarm on (red led at door), I still was able to start the car, then the hazards came on. I don't know if an immobiliser should also be part of the system, but I'm glad that didn't complicate matters further!

 

[Dec]

It’s normal to have no LED on the driver side motion sensor, only the passenger side has the LED.

That passenger side motion sensor will only flash when it detects motion, if you can see it flash while you are driving or if the car has been unlocked and the Green lights have been flashing …to indicate the unlocking of the car… then the alarm is armed and was not disarmed when you unlocked the car.
The one button flip out remote fob button unlocks the car and disarms the alarm, is the remote fob working properly, did it pass the test above?
I think your alarm is permanently on and only a working remote fob will disarm it, your alarm or your vacuum pump doesn’t have an immobiliser, that’s why you can drive with the alarm armed.

How many wires go into the siren? It should be screaming when the alarm is triggered.
What year is the car?

Dec

 

[jonsheaf]

Thanks, I just did the fob camera test and when held down, I get an initial bright flash of white which then becomes a less intense rapid white flashing. Is this right? (I'm holding down the fob button all the while).

I'll check the siren wires when I can get out to it, I did notice it had one of those circular key holes on it for disabling (?)

Car is a 95/96.

 

[jonsheaf]

Looking at the pic above, it's just dawned on me... should I necessarily have a separate alarm fob as shown? Because I only have the merc fob. I assumed it all armed disarmed from that, and it did kill the hazards from going off when the (silent) alarm went off.

 

[Dec]

You will get a flash of Red after 1 second to show that the fob batteries are ok and the white flash as long as the button is pressed, the remote seems to be ok but try synchronising the remote as described below.

If you are in possession of a round type key then you can turn off the alarm on the siren via that circular key hole.

Dec

 

[Dec]

Looking at the pic above, it's just dawned on me... should I necessarily have a separate alarm fob as shown? Because I only have the merc fob. I assumed it all armed disarmed from that, and it did kill the hazards from going off when the (silent) alarm went off.

It seems the remote is working properly and it seems to be arming and disarming the alarm ok so there would be no separate fob like in my picture above, so all that is at fault is that you have a dead alarm siren.

When you press the remote button you disarm the alarm and the car should also unlock, but the vacuum pump is not running when you unlock with the remote fob so the next step is to get another vacuum pump or fix the one that you have, perhaps it just has dirty electrical connections or a fault on the circuit board inside the pump.
Open it up and have a look.

Dec

 

[jonsheaf]

this is great stuff, I will have a look inside the pump ( I used to be a wireman years ago so handy with an iron if need be).
Now how do the yellow vac pipes come off without damage to the connectors?

 

[Dec]

Not sure of the correct way but below is how I do it.

Dec

 

[jonsheaf]

Okay, so I had the pump out, looks like it's been out before judging by the stress marks on the tabs, and the fact half the foam cover around the pump was missing.
All looked okay as best as the eye can see, so I sprayed the relays and long pins with a switch cleaner and put it all back together. ....Same. Remote has no affect on the locks yet the pump makes 3 quick noises as it "tries to lock the car" ( red led flashes and hazards flash)
Opening locks from the door or boot, and it still relocks itself almost before you get a chance to grab a handle!
I want to try another pump but looking closely at what I thought I could use (pump ###1348) and there's a pin missing compared to pump ###2148. The only replacements I've found are on ebay USA at the mo....

 

[jonsheaf]

Thanks again Dec, there was a handy removable section that carried all 6 pipes, I just had to slide off a locking collar.

 

[neilrr]

I'm confused, ideally what pump # do you need?

 

[jonsheaf]

Its central locking pump 124 800 21 48

 

[Dec]

Have a look at this here… r129 central locking problem - Page 4 - Mercedes-Benz Owners' Forums

It explains how the timing of how long the pump runs for, yours seems to be not running for long enough.

It’s possible to plug the electrical connections into the circuit board without the need to put it all back together or connecting the 6 tubes, you will be able to observe how it responds to the remote fob signal and perhaps make some fine adjustments as described in my link above.

Don’t know if your pump internals are the same as the one pictured, a picture of your pump internals might be useful… if you could put one up.

Dec

 

[jonsheaf]

Brilliant! I may attempt to tweak mine. (Inside is identical to that pic!)
Although...when using the key, the pump does manage to lock/unlock the doors and the pump makes a sound as it does so. Original problem is that the remote and pump aren't talking???