key fobs mystery

[Rsolaregolf]

So the "replace key fob battery" warning came on the other day. I check and it had 3.03V so I replaced it with a new one CR2025, 3.32V, no good. The Little red LED on the fob didn't light up when a fob button was pushed. I got out the spare fob and put in a different new CR2025, 3.30V...no joy either. So I took a new CR 2032, 3.30V I had on hand and tried putting it in. Because of the increased thickness of the battery the cover over the battery couldn't be fitted but when pushing the fob buttons the LED came on and the car unlocked. OK I put the new CR2025s back in each fob and now they work?????? I'm scratching my head over this one.

 

[2016golfse]

Bent, misaligned, or debris on the contacts of the key fob?

 

[Rsolaregolf]

nope, popped the old one out and the new one in using a small pick in the slot provided to do so.

I didn't do anything different after trying the 2032 and getting the red LED on the fob to work. I just put the new 2025s back in both fobs and they workrd fine. I'd have a hard time believing it it I hadn't seen it with my own eyes.

 

[Rsolaregolf]

quick update, I drove it this AM no issues, locking/unlocking normally and no "replace key fob battery" nor "key not in range" messages. Weird to say the least. I'm keeping spare 2032 and 2025 batteries in the glovebox to ward away evil spirits.

 

[RonDawg]

Don't keep spare batteries in the glovebox. The heat will almost surely kill them long before you actually need them.

 

[Rsolaregolf]

pretty cool climate here in northern NH, I'm looking at white mt tops right now. I'll keep some spares in the house too.

 

[JoulesThief]

pretty cool climate here in northern NH, I'm looking at white mt tops right now. I'll keep some spares in the house too.

Store your spares in the refrigerator.

 

[P63]

So the "replace key fob battery" warning came on the other day. I check and it had 3.03V so I replaced it with a new one CR2025, 3.32V, no good. The Little red LED on the fob didn't light up when a fob button was pushed. I got out the spare fob and put in a different new CR2025, 3.30V...no joy either. So I took a new CR 2032, 3.30V I had on hand and tried putting it in. Because of the increased thickness of the battery the cover over the battery couldn't be fitted but when pushing the fob buttons the LED came on and the car unlocked. OK I put the new CR2025s back in each fob and now they work?????? I'm scratching my head over this one.

The anode and cathode tabs in the fob can sometimes become oxidized. I recently had a fob that was dead, I grabbed a pencil eraser, polished the tabs a little, put the same battery back in, and it's working fine.
It sounds like the thicker battery might have either had less oxidation on its own surface, or maybe you pushed it extra hard (WAG) or ?

 

[P63]

Don't keep spare batteries in the glovebox. The heat will almost surely kill them long before you actually need them.

QFT

 

[Rsolaregolf]

So the "replace key fob battery" warning came on the other day. I check and it had 3.03V so I replaced it with a new one CR2025, 3.32V, no good. The Little red LED on the fob didn't light up when a fob button was pushed. I got out the spare fob and put in a different new CR2025, 3.30V...no joy either. So I took a new CR 2032, 3.30V I had on hand and tried putting it in. Because of the increased thickness of the battery the cover over the battery couldn't be fitted but when pushing the fob buttons the LED came on and the car unlocked. OK I put the new CR2025s back in each fob and now they work?????? I'm scratching my head over this one.

The anode and cathode tabs in the fob can sometimes become oxidized. I recently had a fob that was dead, I grabbed a pencil eraser, polished the tabs a little, put the same battery back in, and it's working fine.
It sounds like the thicker battery might have either had less oxidation on its own surface, or maybe you pushed it extra hard (WAG) or ?

Nope, the fob I was using daily even though I got the "replace" message was working fine with the old battery. I closely checked the contacts in the fobs and the new batteries as well. All was fine, I know what oxidation looks like. The mystery continues but the fob has worked perfectly for 10 days now.