2001 V70 T5 Remote Keyless Entry Fix Thanks to Vegasjetskier

[Doug S]

I recently solved a remote keyless entry problem with my 2001 V70 T5 and wanted to thank vegasjetskier for his step by step post of an auto dimming mirror repair that helped me get through this. From what I can tell the problem I was having is not common but it certainly was an annoying intermittent problem where my key fobs (both of them) wouldn’t unlock/lock my car.

Took the car to the dealer and they couldn’t determine with certainty which (expensive) electronic module was causing the problem so no help there. The problem was heat related, my remotes would not work during the day but would at night and in the morning or all day when it was cloudy. Knowing the receiver for the remote keyless entry is in the upper electronic module (UEM in rear view mirror) and to confirm it was a heat related I heated up the area around the mirror with a heat gun and sure enough I could create the problem and when things cooled back down the remotes started working again.

Even knowing with certainly it was the UEM I was not in a position to spend the amount of money required to replace the module. With the help of vegasjetskier’s post I took the rear mirror out and apart. I hooked it back up in the car with the electronics exposed and used a soldering iron to heat up localized areas and found the exact component affected by the heat. I have some background in electronics (just enough to be dangerous) and decided I could replace the dying 50Mhz crystal causing the problem. Purchased a used mirror assembly from a local salvage yard and ended up replacing the entire receiver board because it didn’t have the same component I needed. Did some research and determined the receiver board is only that, the key security code and other software for the UEM is contained on the main board stuck to the back for the mirror so no issue with software reloading. The receiver board is soldered onto this main board. Anyway, I replaced the receiver board and all is well now.

UEM receiver.jpg (137.92 KiB) Viewed 5228 times

UEM receiver removed from main board.jpg (132 KiB) Viewed 5228 times

Thanks to vegasjetskier and this detailed auto dimming mirror repair post, couldn’t have done what I did without it
https://www.matthewsvolvosite.com/forums ... 5495#65495

[MadeInJapan]

Thanks for posting back and kudo's to Vegas!!!

[jared25m]

Thanks for posting! I have a few follow up questions:

I'm having the same problem--key fob works in cold weather but not in warm weather. I purchased a used, manual mirror because I wanted to replace both the receiver board and the broken auto-dimming mirror. However, I ran into a few problems. First, the electronics for the manual mirror look different, including the receiver board. I tried to change receiver boards anyway but failed because I had too much difficulty de-soldering the receiver boards. The solder would not liquify. Should I try using two soldering irons? Also, assuming I have better luck de-soldering, should I buy an auto-dimming mirror to ensure matching receiver boards?

Thanks, Jared

[jman294]

Even knowing with certainly it was the UEM I was not in a position to spend the amount of money required to replace the module. With the help of vegasjetskier’s post I took the rear mirror out and apart. I hooked it back up in the car with the electronics exposed and used a soldering iron to heat up localized areas and found the exact component affected by the heat. I have some background in electronics (just enough to be dangerous) and decided I could replace the dying 50Mhz crystal causing the problem. Purchased a used mirror assembly from a local salvage yard and ended up replacing the entire receiver board because it didn’t have the same component I needed. Did some research and determined the receiver board is only that, the key security code and other software for the UEM is contained on the main board stuck to the back for the mirror so no issue with software reloading. The receiver board is soldered onto this main board. Anyway, I replaced the receiver board and all is well now.

UEM receiver.jpg


UEM receiver removed from main board.jpg


Thanks to vegasjetskier and this detailed auto dimming mirror repair post, couldn’t have done what I did without it
https://www.matthewsvolvosite.com/forums ... 5495#65495

How did you desolder the receiver board? Did you replace with a new one? I am having difficulty with this step. Did you keep the pins on the receiver PCB, or simply snap them? Thanks.

[firstv70volvo]

Even knowing with certainly it was the UEM I was not in a position to spend the amount of money required to replace the module. With the help of vegasjetskier’s post I took the rear mirror out and apart. I hooked it back up in the car with the electronics exposed and used a soldering iron to heat up localized areas and found the exact component affected by the heat. I have some background in electronics (just enough to be dangerous) and decided I could replace the dying 50Mhz crystal causing the problem. Purchased a used mirror assembly from a local salvage yard and ended up replacing the entire receiver board because it didn’t have the same component I needed. Did some research and determined the receiver board is only that, the key security code and other software for the UEM is contained on the main board stuck to the back for the mirror so no issue with software reloading. The receiver board is soldered onto this main board. Anyway, I replaced the receiver board and all is well now.

UEM receiver.jpg


UEM receiver removed from main board.jpg


Thanks to vegasjetskier and this detailed auto dimming mirror repair post, couldn’t have done what I did without it
https://www.matthewsvolvosite.com/forums ... 5495#65495

How did you desolder the receiver board? Did you replace with a new one? I am having difficulty with this step. Did you keep the pins on the receiver PCB, or simply snap them? Thanks.

I used solder wick to remove the solder on the receiver board pins but did have some problems removing the pins cleanly. I replaced with a used receiver off a rear view mirror purchase at a salvage yard. I recall having to use some short bare wire to repair broken pins. The challenge is getting all the solder out of the holes and it might have been better to use a hand held vacuum solder sucker, which I didn't have at the time. In any case the repair with the replaced receiver board is still working fine many years later. It can be done and no re-programming is needed. At the same time I also converted to a manual dimming mirror, which I like a lot better because it's darker than the auto dimming mirror.

Edit
To have the best chance of getting the solder out of the holes cleanly invest in a good solder sucker tool (see video) and have a decent soldering iron. On the underside of the board heat the solder for each pin completely and use the solder sucker to suck all the old solder out of the hole, which will prevent damaging the pins. Sometimes it helps to add new (more) solder to the existing pin soldered in the hole as it helps heat up the old existing solder more thoroughly. With all the solder removed from the hole it may also be necessary to heat the pin if it still stuck to the side of the hole with a trace amount of solder. One heated you can push the pin towards the center of hole to free it completely.