I have a CMG Infinity LED flashlight. Some time ago it developed a problem. I would turn it on and it would work for a period of time, sometime very breifly, and then turn itself off. Yet other times it seems to work okay. I've tried new batteries and have cleaned the contacts in the flashlight as well as the battery. I really like this light but with its intermittent operation I can not rely on it. I can not figure this thing out. Has anyone else had similiar problems with LED flashlights?

I have not had any trouble with my CMG Infinities, but I've run into some issues with a similar design - the ARC AAA.

Check you battery for damage. Is there a dimple in the bottom from that little bump contact in the bottom of the Infinity? I've had batteries continue to work with this dimple, but some have failed. You can put alot of pressure on a battery with the screw-to-turn-on lights, (this is what causes the dimple), to the point of causing battery failure.

Cleaning contacts is highly recommended. Use a pencil eraser to get the bottom of the Infinity tube. Don't forget to clean the threads where the head screws on too. These can get gunk covered as well, and will cause conductivity problems. I just wad up a Kleenix and stick it in there and twist it around myself, but you would go more hard-core with a toothbrush and some alcohol if needed.

Older ARCs also need to have a "roll crimp" put into the head for reliably. Infinities do not need this AFAIK. Maybe others can answer if they have Infinities that require this modification like older ARC AAA's do.

I had a very similar problem with a Gerber AAA LED. I actually retired it because I thought it was totally dead. Then one day I picked it up and it came right on. Hmmm. Not sure what the problem is, like you I tried cleaning, battery and all that. I do not consider it reliable and no longer carry it.
I have Peak Matterhorn AAA and it has been fllawless. I plan to buy a few more soon. A great little light, I have the extra power version. Cheers

Be careful not to leave residue on the contacts from the pencil eraser. Be sure that it is a new, clean eraser. Electrical contact cleaner is good stuff. This is carried by Ace hardware. I use CRC QD Electronic Cleaner.

i had a similar problem with a couple of old original CMG infinities, but that was years ago.

on my arc AAA (old and new one) i've had good results using 91% rubbing alcohol on the contacts and a pencil eraser.

ditto what haertig wrote.

I have had and Infinity Ultra for several years now. It sounds like you have dirty threads. There is a special grease that will maximize the flow of electricity between the body and LED head and make it easier to turn the LED head.

Having had the same or very similar problems with my CMG in most cases a good cleaning like the others have mentioned will usually fix the problem.

But along with cleaning the contacts some times gunk and lint from your pocket will pack into the rim between the body and the head. Since you open this gap to turn the light off if it gets filled up it can keep you from tightening the lid down far enough to make contact. But turning it off and on can disturb this build up to be refilled later in your pocket. This will often cause eradic operation. So if it doesn't want to light try loosening the head and run a thumbnail through the gap.

As a last resort some of the early models were a bit to long or the threads were not deep enough for the battery to make good contact. Even with the head screwed down all the way it was iffy at best weather it would work. Some times you get a battery that is just a hair longer that works great. The reverse of the dimpling problem mentioned. If this is the case you need to shorten the distance. Since you can't actually shorten the case you need to do the next best thing. Cut a disc of aluminum foil the size of the inside of the case. Drop it into the bottom and stick in the battery. Even the thin sheet of foil should give you the extra distance needed. The sheet will wear and need to be replaced. By normally only when changing the battery.

If you've cleaned the contacts, remaining suspcts are the roll crimp and broken traces on the PC board from flexing. Ask over in candlepowerforums how to fix it.