Remote locking interference

[aizvara]

Not sure General Gassing is the right forum, but here goes:

I've got a weird problem with my car's central locking. Just started earlier this evening; I found I could no longer unlock or lock the car with either of its remote key fobs. I assumed it was a flat battery, but the car unlocks and works fine the old fashioned way (aside from the alarm sounding). I drove off a short distance (100 metres) and could then lock with the remote, so my guess is that its some sort of localised interference. This seems to be backed up by some web searching, in that most car key fobs use 433Mhz and that frequency is apparently also used by some other devices, which may interfere. Great.

So, has anyone else experienced this? Any ideas on sorting it out (hopefully something short of building a faraday cage around the car)? And does anyone have any idea of the sorts of devices which can cause this blocking effect? Mostly out of interest, as I'm half expecting the problem to go away when whichever neighbour it is turns off their garden-shed fusion reactor experiments.

[Paul Drawmer]

433Mhz is used for a lot of stuff. As well as remote key operations, there are low power transmission, typically wireless speaker and video systems in the home, I think there is till some PMR(walkie talkies), police and marine usage. There is also a section licensed to the Amateur Radio band.

All of the licenced use equipment will have strict standards for the quality of transmissions, and the receivers will be designed to be very selective on what they do and don't pick up.

The problem is that key fobs are very crude and can be 'deafened' by the transmissions from a legitimate user nearby.

I had a similar problem some years ago when my 325 wouldn't work with the remote when I visited my son. Turns out that the house over the road was a 'semi secure' unit where some of the residents were tagged to prevent them wandering off and getting lost.

It's the car makers fault, they adopted a technology that wasn't suitable. Renault were the most effected, but there's very little you can do about it.

[aizvara]

Thanks for the detailed explanation! I assumed there wouldn't be much I could do about it. As it turns out, the problem appears to have lessened this morning; I can now open the car when very close by.

I guess I'll be asking the neighbours what they've recently installed/switched on. I think I heard one of their car alarms going off this morning, so others are probably experiencing the same issue.