Battery charger model 1400666 not charging The red led is not on.this is a 12 volt charger.

Question edited for clarity and correct spelling of the maker.

Here is the manual section on the LED Lighting sequence. Both Red and Green flashing is not there. Your charger has a model number on the bottom of it and you didn't supply that, so this may be the wrong charger!
http://powertool.manualsonline.com/manuals/mfg/ridgid/140276002.html?p=5

The question was mentioned on Fixya before.

I have a ridgid rapid twin 18 V charger that flashes red and

Fixya https://www.fixya.com > Forum > Drills > Ridgid
Nov 21, 2019 - Red flashing means the charger or battery is to hot and must cool down before it will charge. The charger will not charge a battery if the lights are flashing.
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the trimmers switch may be faulty.

CHARGING THE BATTERY PACK
Battery packs for this tool are shipped in a low charge condition
to prevent possible problems. Therefore, you should
charge them until the green LED on the front of the charger
comes on.
NOTE: Batteries will not reach full charge the first time they
are charged. Allow several cycles (operation followed by
recharging) for them to become fully charged.
CHARGING A COOL BATTERY PACK
See Figure 3.
If battery pack is within normal temperature range, the red
LED on charger will come on.
NOTE: If the charger does not charge the battery pack
under normal circumstances, return both the battery pack and
charger to your nearest Ryobi Authorized Service Center for
electrical check.
n Charge the battery pack only with the charger provided.
n Make sure the power supply is normal household
voltage, 120 volts, 60 Hz, AC only.
n Connect the charger to the power supply.
n Place the battery pack in the charger aligning raised rib
on the battery pack with the groove in the charger.
n Press down on the battery pack to be sure contacts on
the battery pack engage properly with contacts in the
charger.
n Normally the red LED on charger will come on. This
indicates the charger is in fast charging mode.
n Red LED should remain on for approximately 1 hour
then the green LED will come on. Green LED on
indicates battery pack is fully charged and charger is
in maintenance charge mode.
NOTE: The green LED will remain on until the
battery pack is removed from the charger or charger is
disconnected from the power supply.
n If both yellow and green LEDs come on, this indicates
a deeply discharged or defective battery pack.
Allow the battery pack to remain in the charger for 15
to 30 minutes. When the battery pack reaches normal
voltage range, the red LED should come on. If the
red LED does not come on after 30 minutes, this may
indicate a defective battery pack and should be
replaced.
n After normal usage, a minimum of 1 hour of charging time
is required to fully recharge battery pack.
n The battery pack will become slightly warm to the
touch while charging. This is normal and does not
indicate a problem.
n Do not place the charger and battery pack in an area of
extreme heat or cold. They will work best at normal room
temperature.
NOTE: The charger and battery pack should be placed
in a location where the temperature is more than 50°F
but less than 100°F.
n When batteries become fully charged, unplug the
charger from power supply and remove the battery
pack.
Source(s):http://toolboyworld.com/eBay/Ryobi_P110/...

Should use proper 24 volt 2-4 amp off-board charger. A 3 red, 3 green flash code on a VSI/Remote Plus controller indicates high battery voltage.

Could be.Those batteries leak charge even when not in use.I would let it go for 24-48 hours just to be sure.Unless the batteries or charger becomes very hot.

I really don't have any idea as to what you're talking about here other than a battery and maybe a charger. Seems as if you're saying that you have a 12 volt 1.5 amp automatic battery charger connected to a 12 volt, 8.5amph battery but the red light on your charger is blinking. The blinking red light indicates that the charger is not seeing a proper connection such as crossed polarity connection or simply a poor connection. You say that the battery voltage has dropped from 12.5 volts to 9.1 volts with the charger connected. If this is the case, the battery is badly discharged and the charger is not charging the battery for some reason. The charger may be bad but check the connections to make certain they are correct and good. If they are, I'd replace the charger.

Good luck
Steve

If you are comfortable with removing the upper half of the housing, unplug charger and remove the screws, take a look at the circiut board for a "cold" solder joint or broken component, usually the round ceramic looking piece with the copper wire around it. but look at the whole board.

Here is the manual:
http://toolboyworld.com/eBay/Ryobi_P120/P120_566_eng.pdf

Red = quick charge
yellow = evaluating
green = charged

CHARGING A COOL BATTERY PACK
If battery pack is within normal temperature range, the red LED on charger will come on.

Red LED should remain on for approximately 1 hour then the green LED will come on. Green LED on indicates battery pack is fully charged and charger is in maintenance charge mode.

The control systems on power mobility equipment have a "prevent" circuit that immobilizes the equipment while it is plugged into a charger, so folks won't take off with it plugged into the wall outlet. When you turn it on when plugged into a charger, the display will flash constantly, or sweep constantly, depending on the manufacturer. This is normal. Your off-board charger should have a red light to indicate power to the charger, and another light for the charge status. Yellowish means it is charging, when it turns green, you are fully charged. If the status light is green all the time, that is an indication that the charger is not functioning properly, or that the batteries are below a chargeable state. Check charger output, which should be 26-28 volts dc, and each battery should show at least a 12 volt reading, but around 13.5 volts with a full charge. If one or both of the batteries drops below 12 volts after a short period of time, it's time for a fresh pair. Fully charge new ones before using the chair.