Key Fob working intermittently

Ppashley · Post by **Ppashley** » 19 Dec 2011, 08:26

My remote key fob is working intermittently on my xc90 which I bought used last week.

I hear there may be some issues with the remotes?

I've changed the battery today and range increased but car did not respond to all of a series of lock/ unlock commands when I tested it.

It seemed to recover after a pause of about 20 seconds or so.

Is this a feature or a something unusual?

I understand that there may be a technical issue and new fobs are available under warranty ?

Anyone else had / resolved this issue?

Thx

owl · Post by **owl** » 06 Jan 2012, 12:54

When I bought my 04 XC90 the key fob wasn't working. When I replaced the battery it was so hard to get it to work that I thought it was broken. Only after a couple of days I realized that if a tried for long enough it would work. I solved the problem by adding an antenna (a short piece of wire inside the key fob) to the output transistor. It is a dirty hack, but it did the trick.

Basically your key fob is made of 3 main parts. A microcontroller that generates the signal, then a modulator that takes this signal and modulates a waveform that is amplified by the output transistor that transmit it through the antenna. Any of these parts can be failing, but if it is a weak signal problem I would bet for the output transistor. When a microcontroller fails, it fails for good.

If you can solder, you can try replacing the transistor, and if that doesn't work, you can try replacing the modulator. I was too lazy to try this, so I just tried adding a wire to make a bigger antenna and it worked very well. It went from a remote that I would have to try several times very close to the car to make it work, to a perfectly functioning remote.

What year is your car? Your remote might be different from mine. Does your signal seem to be weak, i.e. how far/close do you have to be to make it work?

Last piece of advice: If you are under warranty, don't mess anything and try to get a replacement first. If that doesn't work, don't try to buy a remote from ebay or other unreliable source. This remotes come with a code that needs to be programmed into the car to make it work (you need a dealer for this), and you will not be able to get this code if the remote is used.

Bonzooo5 · Post by **Bonzooo5** » 21 Sep 2013, 14:07

: 2004 V70 Fob Circuit Board; V70-04FOBCB.jpg (267.05 KiB) Viewed 9959 times

Great idea. On the circuit board where is the antenna? Also how long was the piece of wire you soldered?

kcv70 · Post by **kcv70** » 12 Nov 2013, 10:28

My 2012 XC90 has one key fob that acts up and won’t work about 70% of the time. It won’t lock or unlock the car at any distance. The second fob works fine. Replaced under warranty 11/11/13. From nhtsa.org…

Volvo Service Bulletin # TJ23170
Manufacturer: Volvo Cars of N.A., LLC

SUMMARY:
VOLVO: NOT POSSIBLE TO LOCK/UNLOCK THE CAR WITH KIR. NEW REMOTES HAVE BEEN INTRODUCED INTO PRODUCTION FROM STRUCTURE WEEK 201215.

gjlv70 · Post by **gjlv70** » 25 Dec 2013, 13:54

Hi,
I have a 2010 XC90 65000 miles, have replaced the drivers door window/lock panel twice now and after about 6000 miles after the last swap the key fob and door lock combination plays musical tunes(not really). Press the key fob to unlock or lock and the door lock will go up, then down, then up then try up and ... After they music stops its 50/50 if the door is actually unlocked. If it is still locked, pressing the key fob to lock then unlock works. Batteries in the Key fob are new.
Is this a software issues by chance?
thank you for the reply

Drugiboksar · Post by **Drugiboksar** » 12 Nov 2018, 13:35

You can boost the transmitting power by adding a 100 ohm resistor to the transmitter. By adding a aditional 50 ohm resistor to the reciever antenna you can make the receiver picking up less interference ( from weather stations on 433 MHz) - hence making it a bit deaf, only receiving a strong signal from ( hacked) remote.