75ZT Community

The latest acquisition ( 54 plate 190se, pictures to be up soon!!) has had a few issues, mainly of a watery variety! With the standard issue blocked plenums and sunroof drains, they *touch wood* appear to be sorted.

The next problem is with the keys and starting the car, both keys are without batteries so the only way to lock/unlock is by putting the key in the door. It does that fine with no blip of the horn. Now when you put the key in the ignition all the electrics power up and when you turn the key all the way to start her up nothing happens and when you release the key it then locks the barrel. The battery has been fully charged and disconnected until today. The car came with no batteries in the fobs and ran fine then so it's all a bit puzzling.

Does the chip in the key need a battery to work or is it the immobilser which is not recognising the keys?

Chip for the immobiliser doesn't need the key battery. There's a coil around the barrel in the ignition switch that powers up the chip.

Are you getting a warning light and beeping noise from the dash? Certainly the highline instrument do this if the immobilser can't read the chip, and I thought the lowlines did too.

I have seen problems with the relay in the immobilser, or it could be as simple (?) as the starter solenoid or wiring.

When you say the barrell is locked, could you clarify what you mean? There's a feature where you can't turn it to the crank position more than once unless you turn it completely off first, I think. (I have different cars and can't remember if the 75 has it for sure).

Duncan wrote:Chip for the immobiliser doesn't need the key battery. There's a coil around the barrel in the ignition switch that powers up the chip.

Are you getting a warning light and beeping noise from the dash? Certainly the highline instrument do this if the immobilser can't read the chip, and I thought the lowlines did too.

I have seen problems with the relay in the immobilser, or it could be as simple (?) as the starter solenoid or wiring.

When you say the barrell is locked, could you clarify what you mean? There's a feature where you can't turn it to the crank position more than once unless you turn it completely off first, I think. (I have different cars and can't remember if the 75 has it for sure).

By lokced that's what I meant, I remember now that is normal when you don't turn it completely off!!

No there are no beeps or warning lights flash up. I have had the carpet out to get it dry so most of the interior was out, I didn't unclip the immobiliser but thinking about it might be worth seeing if the plug has become slightly dislodged.

Might be worth checking your immobiliser plug to see if got wet and the contacts have rusted up resulting in a poor connection

Alan wrote:Might be worth checking your immobiliser plug to see if got wet and the contacts have rusted up resulting in a poor connection

Yes, good idea. Check the white and red wires on the big pins in particular.

Looking at this from a slightly different angle it could be a fault on the starter sol, either the small actuator wire to the sol has corroded and not making contact or the solenoid contacts have failed. the battery and immobiliser could be a red herring

Had a call from home this evening, as Dad's had a look at it whilst the car's at mine.

- Someone's been in the immobiliser and it's not the original unit (it states is a replacement part I am lead to believe.

- Above has signs of water ingress but no corrosion.

- When the igntion is switched on, the fuel pump primes etc as per normal

- Relay 4 starts to tick when key turned to start the car. swapped with another and it does the same.

- battery is healthy (although trying another tomorrow in case)

Stupid part being it drove from Manchester to my house and would start for days after it got here!

After looking at the wiring daigram and some extreme cable chasing we found the fault was with the wires that go into the immobiliser. Some of them have been cut and very crudely put back together with what can only be Tesco value solder and a roll of electrical tape. One of the wires (red and white) which come from the ignition was only held together by tape, so whith panels being removed to take the carpet out it got disturbed so wasn't making a good contact anymore so immobiliser wouldn't allow the car to start. Put a connector in where the captain gaffer tape joint was and it fired up straight away. All that's needed now is some proper solder with heat shrink and it should be ok on that front (hopefully!!!)

good news richard and well done

Thanks for posting the solution. It helps others if they see a similar problem.