Key fob stopped working

Penhallow · Post by **Penhallow** » 30 Aug 2020, 10:56

It has been erratic recently and now stopped completely , battery is new (3v) took the thing apart , used Switch cleaner , even checked for continuity through the switches, and traced the circuit board within reason , no problem locking/unlocking via key and starting , Flashers Flash !! Any Fixes or Ideas Please ? 2003 / 2.4 D/ V70 .

Post by **oragex** » 30 Aug 2020, 11:48

Is it just the fob for them doors ? Try removing maybe the siren module fuse. Otherwise, I believe the receptor is inside the cabin rear view mirror. If it's rather the fob electronics, maybe bring the circuit to a TV shop and ask them to check the small components

Post by **firstv70volvo** » 31 Aug 2020, 09:22

I had an intermittent problem with my key fob not working years ago and it turned out to be a bad component on the receiver board in the rear view mirror. My problem was temperature related, when very hot the key fob wouldn't work and I was able to pinpoint the exact component on the receiver board (crystal oscillator) using a heat gun.
I had originally took the car to the dealer and they said they couldn't determine the problem and thought it was either the CEM or UEM(in rear view mirror), both approximately $1000 a piece to replace at the time and they wanted me to pay for both if the first one didn't fix the problem. Disgusted with the dealer I found the problem in receiver board and purchased a used rear view mirror from the salvage yard for $50 and transferred the receiver board from the salvage part. Transferring only the receiver board eliminated the need to buy and reprogram the main UEM board in the rear view mirror. The receiver board is the small vertical board attached to the main UEM board (see photos). It's somewhat tricky to remove the soldered connections of the transmitter board but doable if you're careful and have a good solder sucker tool. What makes it difficult is getting all the solder off the connectors and the use of small individual connector clips for each soldered connections.

Not sure if your problem is the transmitter board or not but wanted to provide you with this information. If you have two key fob's and both don't work then there is possibility it's a problem with the receiver board. Does you sunroof work, which is controlled by the UEM? Have you done the reset of the UEM by unlocking and locking the front door with your key several times?

Post by **darrylrobert** » 01 Sep 2020, 03:31

nice pics, ive found on my 2001 xc70 and other Volvo's is the solder goes soft and just needs to be reflowed with new solder. I think you can test to see if its transmitting a signal using an analog TV if you know the frequency. Does anyone know??

Penhallow · Post by **Penhallow** » 02 Sep 2020, 09:29

Thanks for ALL the replies and slowly eliminating each reply as I go through the system !! Interesting about HEAT !! it has been for the last 4 months hitting the middle 50's ! Maybe I should have covered the interior mirror ? Thanks again for the Help.

Post by **oragex** » 02 Sep 2020, 12:20

Placing some insulating material should help reduce the direct heat in sunny days. Otherwise, the easiest is to bring both the fox and the above mentioned receiver to a local TV shop. Keep the car battery disconnected. Ask them to check the boards

Penhallow · Post by **Penhallow** » 15 Oct 2020, 08:34

Hi, back again, done most of the suggestions, but this last week locking /unlocking with key in lock sometimes it only unlocks the drivers door ,have to re-lock and again unlock and all 4 doors can now be opened , is this happened to any members ?

Post by **jonesg** » 15 Oct 2020, 17:28

Penhallow wrote: ↑15 Oct 2020, 08:34 Hi, back again, done most of the suggestions, but this last week locking /unlocking with key in lock sometimes it only unlocks the drivers door ,have to re-lock and again unlock and all 4 doors can now be opened , is this happened to any members ?

that sounds like normal.
first click only unlocks driver door, to open all doors click remote again.
thats hpw mine works, 04 v70.

Penhallow · Post by **Penhallow** » 16 Oct 2020, 09:02

Thanks for the reply jonesg, I can only use the key at present , remote not working !

Post by **jonesg** » 16 Oct 2020, 21:40

Penhallow wrote: ↑16 Oct 2020, 09:02 Thanks for the reply jonesg, I can only use the key at present , remote not working !

I never lock mine, mostly Amish around here, they're not big car thieves.
Lock your horses up.