Unreliable electronic key-help!!

[1rotty 40]

The key on one of my e39's is really unreliable when I use the remote to lock or unlock the car.The key battery is fine.Also I'm not convinced the alarm sets as the mirror light doesnt activate.

Anybody had a similar problem ( my 740 was the same).

Would be really grateful for your suggestions.

[jochen 4]

The key on one of my e39's is really unreliable when I use the remote to lock or unlock the car.The key battery is fine.Also I'm not convinced the alarm sets as the mirror light doesnt activate.

Anybody had a similar problem ( my 740 was the same).

Would be really grateful for your suggestions.

A lot of people get confused with these cars.

If it is a NZ-new car, then the remote is a wireless remote that uses 433MHz radio frequencies, and the antenna on the car is in the rear windscreen. The range is good. If the car has the alarm option fitted, then the 'clown nose' on the rear view mirror will blink when the alarm is set.

If however the car is an ex-Japan E39, then it is very different.

The remote is an infra-red remote, and the clown nose is the infrared receiver.

Japan cars normally do not have the alarm fitted, so the clown nose will never flash (it has no LED inside it) (and no one steals cars in Japan)

The range of the key is directly governed by whether the key can 'see' the clown nose.

A lot of people hold the key too low, and the signal is obstructed by the door panels and other vehicle bodywork.

Or too high, and the roof prevents the signal from getting to the rear view mirror.

So practice pointing the key at the rear view mirror from a location where the infrared beam will shine through the windows. Remember, your eye height is not the same as key height - so just because you can see the mirror doesn't meand the key in your hand can!

I have had a lady come to me and show me the new alarm and central locking remote control she had fitted to her E39 because the original key was "unreliable". I proved it otherwise, and once she realised that the key needed to see the rear view mirror, then the original key became 100% reliable to her as well :-)

Another issue that impacts range of infrared is sunlight. On a bright sunny day, the sun emits infrared light and creates interference for the remote control.

At night, I could unlock my E39 with the infrared remote from a distance of easily 20 metres.

At day, a different story!

But always reliable within 2 or 3m from the car, pointing at the mirror through a window :-)

And if all of the above is common knowledge to you, then you may have bad battery contacts. Rremove the battery, polish the contacts with an rubber eraser to make them bright and shiny, and refit the battery.

Tip: for reliability, do NOT touch the battery with fingers! Skin oil causes oxidisation of the battery surface resulting in bad contact after a few years. So use gloves of plastic tweezers, never fingers, when handling button batteries.

Edited June 25, 2008 by jochen

[1rotty 40]

Jochen-you're a legend-thanks very much-isn't it always the simple things that make you look like a dick.

By the way I see a lot of your posts on Bimmerboard etc.Obviously you are a BMW professional & wonder what motivates you to spend the time you do helping dumb arses like me.

[hybrid 1040]

Jochen is just an enthusiast like the rest of us... just with a hell of a lot of electronic knowledge as its his field. He spends his spare time programming up code to talk to more modern based BMWs

[jochen 4]

Obviously you are a BMW professional & wonder what motivates you to spend the time you do helping ...

I wish i got paid for what I do!

As hybrid said - I'm an enthusiast. All my help is for free.

And I have never worked for BMW or a BMW workshop....

Edited June 25, 2008 by jochen

[1rotty 40]

mate i certainly meant no offense,in fact just the opposite.Wasnt suggesting for a moment that you had an ulterior motive

[318Touring 40]

Jochen, thanks for your post up there mate. I always wondered why the heck my Compact's remote only worked some of the time. That was because I was pointing the damn thing down to the body of the car, and not to the rear view mirror!!