We have five Panasonic ACs, which are all over 5 years old, with remotes for each. So no "destruction" books to help. Not having used some of the ACs for a while we suddenly discovered half the remotes not working - and one remote worked up to Saturday morning but failed to switch the AC on Saturday night.

Changing batteries to ones just bought did not seem to make any difference. I could not see any obvious signs of corrosion.

Most non working do not show any display when batteries put in.

The one that most recently won't seem to now work still shows the display (temperature and various bars plus flashing clock sign).

The ones not showing any sign of life - does anybody know why or are they now junk and what is the cheapest option to replace them?

Any suggestions for the one that still shows the display but wont seem to switch on the unit - which can be switched on with one of the two remaining units?

Many air-con remotes have a recessed "reset" button, often hidden behind a sliding panel and sometimes actioned by sticking a toothpick or other pointed implement into a tiny hole. If you change the batteries or have trouble using the remote you may need to push this reset button to get it working again.

You should be able to find instructions on the manufacturer's website.

Mine died a few years ago and I found cheap replacements at the market (in Pattaya). So if they can't be reactivated per KittenKong's suggestion, you can probably find them in a market or hardware store or a/c installer near you. If you ask around a bit someone will know who has them.

Slightly off topic but is it possible to buy AC units with wall mounted touch pad controls or similar without the need for remote controls?

I believe Amorn stores sell "universal" air con remotes, as well as many brand name model-specific remotes.

Many air-con remotes have a recessed "reset" button, often hidden behind a sliding panel and sometimes actioned by sticking a toothpick or other pointed implement into a tiny hole. If you change the batteries or have trouble using the remote you may need to push this reset button to get it working again.

You should be able to find instructions on the manufacturer's website.

Yes and some of them have a default mode by pressing a combination of buttons.

Play around, can't do any harm, or as suggested, try their website.

I had the same problem with two of the four remote controllers for my split-type air-conditioners. I believe the high heat, humidity or leaky batterie have oxidized the pcb. You can try resetting them. If that does not work, the easiest/cheapest solution is to buy universal remote controllers for air-conditioners. They worked for me. Make sure the replacement controllers are compatible with your Panasonic air-conditioners. (Recommendation: remove the batteries from the remote controllers during long periods of absence from home.)

I had the same problem with two of the four remote controllers for my split-type air-conditioners. I believe the high heat, humidity or leaky batterie have oxidized the pcb. You can try resetting them. If that does not work, the easiest/cheapest solution is to buy universal remote controllers for air-conditioners. They worked for me. Make sure the replacement controllers are compatible with your Panasonic air-conditioners. (Recommendation: remove the batteries from the remote controllers during long periods of absence from home.)

That last point was recommended to me by Irish Air Con and is worth remembering for the future.

Thanks to all for the suggestions. I am back tomorrow so will see.