Strange Central Locking Problem

[John Brennand]

2006 XC90 2.5T. Came to it this morning and the central locking didnt open on the fob press. Used the key went out came back and checked the fuse in the rear compartment - that is fine. Must be the battery in the fob I thought. Changed that and still no good.
However, I have just noticed that if I hold the key fob close to the door windows - it does work! If I back away a few yards, still nothing. I have a spare key/fob and that behaves exactly the same.

Anyone any ideas what may be going on and what to try next ?

[60041]

Is there anything around the car that could be causing electrical interference, such as a radio mast or junction box?
I came across this problem a few years ago when a hospital near where my brother in law parked put some communication masts up on the roof and there was that much radio “noise” that it was blocking out the signal from people’s remote fobs.

[John Brennand]

Originally Posted by 60041

Is there anything around the car that could be causing electrical interference, such as a radio mast or junction box?.

Very unlikely today - car is parked outside my house where it has been parked for the last 18 months with no issues.

I also know that the alarm/siren are ok too - as when I opened the door with the key, it went off until I started the car.

[SwissXC90]

Your symptoms are that the range of the key fob is suddenly greatly reduced.

This is generally some form of local radio interference, which can be confirmed by driving to another location and trying again there, or eliminating anything in the car which may interfere with the remote keyfob.

I have exactly this problem in my car, but I know exactly what the source of the radio interference is - it is my garage door opener, which I have wired to my driver's spotlight switch.
Turn on spotlight, garage door opens. It's great.

But when the garage door opener is running (spotlight is on), my keyfob remote control range is severely limited to just 1m from the receiver, instead of around 20m to 100m.
And the inability to lock the car helps to remind me that I forgot to turn off the garage door opener...

[John Brennand]

Thanks chaps. Came out this evening - still didn't work - did the x3 lock/unlock thing. Drove 250 yds down the road and tried again - and hey presto it worked again. Went back home - didn't work. So looks like your diagnosis is accurate !

As it worked down the road I expect there is nothing in the car causing the problem - but due to exterior interference. Is there any way to track down the source? Would doing a wifi analysis on an app help? What frequency does the fob broadcast on? Likely sources (house alarms? other cars? wifi networks?)?

I have changed nothing in the last 24h that is impacting on the radio frequency background in my area ?

Any suggestions welcome.

[John Brennand]

[QUOTE=
I have changed nothing in the last 24h that is impacting on the radio frequency background in my area ?

Any suggestions welcome.[/QUOTE]

BTW - where is the receiver for the fob signal actually located on the XC90 - might help with some signal troubleshooting

[xco]

Hi John

Is an annoying problem to be sure....

Dont know if this will help but it may be a good idea to have a look at the wi-fi traffic up and down your road .

There is an excellent app for this on Play store called "WI-FI ANALYZER CLASSIC" by Farproc (4.3 rating)

I have tried an awful lot of these over the years but have found this to be the easiest and most informative (discretely)to use.

It will monitor changes to wi-fi traffic up and down your street and may help you discover if somebody has just upgraded their router for instance or signal strength has changed.

Does it happen all the time or just certain times off day?

Hope this helps

[John Brennand]

Originally Posted by xco

Hi John

There is an excellent app for this on Play store called "WI-FI ANALYZER CLASSIC" by Farproc (4.3 rating)

Hope this helps

Is "Play Store" an Android thing? I only use iPhones and there is no App of that name on the App store.

Cheers

[SwissXC90]

Originally Posted by John Brennand

BTW - where is the receiver for the fob signal actually located on the XC90 - might help with some signal troubleshooting

In the interior rear view mirror.

[SwissXC90]

Originally Posted by John Brennand

As it worked down the road I expect there is nothing in the car causing the problem - but due to exterior interference. Is there any way to track down the source?

Yes, use a spectrum analyser.

The remotes operate in the ISM frequency ranges (see https://en.wikipedia.org/wiki/ISM_band), but the receiver can be susceptible to other frequencies. A lot of remotes operate at 433 MHz.

You need a spectrum analyser to scan a frequency band from around 50 MHz to 1 GHz

Something like this:
https://www.rohde-schwarz.com/us/pro...iew_63665.html

The source of interference can be from anywhere local to your house, most likely within around 1 to 5 houses distance.

You can narrow down the area by testing with your car, and making notes on a paper map as to which locations on your street the remote works in, and where it does not.

This will give you valuable information as to where the source of interference is likely to come from

As a first tip, turn off the power to your entire house and see if anything changes. If it changes, something in your house is interfering.

If not. start knocking on neighbours doors and ask if they added any new wireless equipment recently (use the timeframe of when the problem occured)