Help. Alarm won't turn off.

[Iain]

Car: 1998 W202 C250TD auto estate.

Both keys have power. Central locking not opereating to open car via fob. Use slide out key to unlock door and when door is opened alarm goes off. Door locking/unlocking button on dashboard not functioning as are the electric windows not working. Car starts OK and will drive. (not sure for how long though). Siren goes quiet after 10 secs or so and only starts again when door opens.

Anybody had similar problems and what could be the fault?

 

[ringway]

At a guess, check for water ingress around the pse pump (possibly under the rear seat near the battery on your model?

The unit is encased in a foam boot. The foam boot absorbs/draws any water to the pse unit and the circuit boards become damp affecting the operation of alarm, central locking, electric windows..

 

[Iain]

Thanks for that.

I'll have a look and report back.
Checked both keys with camera for operation. All OK.

 

[Iain]

At a guess, check for water ingress around the pse pump (possibly under the rear seat near the battery on your model?

The unit is encased in a foam boot. The foam boot absorbs/draws any water to the pse unit and the circuit boards become damp affecting the operation of alarm, central locking, electric windows..

Just checked. Nothing under rear seat except the footbrake cable mechanism under a steel plate and a couple of quid in loose change!
Do you know of another location for the pse pump? Can't get into boot to check under the large plastic cover that is behind the backrest. Unfortunately the estates don't have electronic boot release like the saloons and my boot has a large toolbox and other items in there stopping me from getting to that area. Can't check fuses or relays adjacent to battery either because of this. Not sure though that there are any that could be related to this.

 

[Iain]

Bumpy.......

 

[BlackC55]

Check all fuses first.

I think the PSE is on the right side behind trim that has to be unscrewed/removed. I can't quite remember though..... I can check tomorrow for you.

 

[Iain]

Thanks Olly found it.
Managed to access the boot and get the pse pump out. Couldn't see any corrosion within and the foam was bone dry so no chance of water or condensation ingress.
Swapped the pump over with another known good pump albeit, one from a petrol model and not made a difference (the part number was slightly different but connections were the same). Now back on its original. One thing I did notice was that the heated rear screen,rear wiper and washer,front wash/wipe and indicators do not work although hazards do. Engine starts and runs. Confusing me Any further ideas please.

 

[ringway]

Thanks Olly found it.
Managed to access the boot and get the pse pump out. Couldn't see any corrosion within and the foam was bone dry so no chance of water or condensation ingress.
Swapped the pump over with another known good pump albeit, one from a petrol model and not made a difference (the part number was slightly different but connections were the same). Now back on its original. One thing I did notice was that the heated rear screen,rear wiper and washer,front wash/wipe and indicators do not work although hazards do. Engine starts and runs. Confusing me Any further ideas please.

The rear wiper is the Orange 40A fuse.

Are you sure the rear windscreen washers don't work?

 

[Iain]

The rear wiper is the Orange 40A fuse.

Are you sure the rear windscreen washers don't work?

Yes. No washers or wipers front and rear. No heated rear screen. No indicators but hazards work heater fan also working

 

[BlackC55]

fuses ok?

 

[Iain]

fuses ok?

Yes. All fuses OK Bright and shiny with no hint of corrosion.

 

[BlackC55]

How about the fuse under the passenger footwell? The BIG one

 

[Iain]

How about the fuse under the passenger footwell? The BIG one

Aah...... you mean the big one under the passenger footwell do you?

I'll have a look in the morning Olly. Bit dark now. At least the alarm is not going off each time I open the door now I have removed the PSE pump!
Thanks for your help.

 

[BlackC55]

Check the voltages to the PSE too.

 

[Iain]

Well the problem is now sorted. I would like to thank all that suggested things that it might be and particular thanks to Olly who got me looking down in the passenger footwell.
The problem turned out to be very slight corrosion in the bank of coloured connectors that sit adjacent to the sill on that side. 1 hour with a needle file cleaning each pin has now done the trick and the old girl is back to normal.
One thing I did observe though was the box(I believe is the front SAM) that sits behind the footplate in that area although dry, the insulation on the wiring too it was soaked in a very light oil. Couldn't find the source of this oil as it only seemed to be for about 9 inches back from the 2 plugs. I have dried this out completely and re-insulated with new tape, but it is still puzzling me as to the source of this oil. Shall have to keep an eye on it.
Thanks to all again.