Quasar single channel remote key fobs has stopped working. Changed battery, no difference. Red light on key fob rapid-flashes while the button is pressed. Other similar remotes the light is constant.

Be sure to use the correct battery, properly in place, clean the key contacts , See owner's manual for additional information.
There are specialized locksmiths for car keys

If the key had gone faulty, the key code must be re programmed on the vehicle computer. This can be done only using a PIWIS tool, available at the dealer or at a qualified Porche garage.
Try also the following reset:
turn ignition on,
turn off.
remove the transponder from the column
push any button on the fob within 6 seconds.
This procedure will reset the key synchronizing again with the vehicle computer.

I recently changed the battery on my key fob for my ssanyong rexton. I then did the following for the key fob to make it work. 1. Enter vehicle and close all doors.

2. Put seatbelt on (or clip it into the buckle) to shut the warning buzzer off.

3. Put key in ignition, turn to run position but don't start it.

4. Press and hold both buttons on key fob until red light on fob stays on. Then let go of both buttons. Then pressed the alarm button then the panic button, somthing like that. To be fair the button sequence after the red light came on is a bit vague. The alarm was blaring so i was happy when it just stopped.

It could be your onboard computer or locking module, as the guy next door had an identical problem on his Megane. A tech came and changed a module then programmed the 'brains'.

all you have to do to reset the coding is hold the lock button down for a minute or two till the locks click locked. then test it again by unlocking them. if the button light flashes rapidly then the batt is low, which will affect the distance for use. (do the re-code right next to the vehicle for best results.)

Does the red light on the remote light up when you push any of the button
if no, replace remote
if yes, then try repograming the remote to the car again.
-Have remotes' ready. if you have two then fob#1 and fob#2 (doesn't matter which one is #1 or #2)
-each step has to be done within 5 sec or it will not work, but don't do it super fast.
1.turn key just to the "on" position (not starting) and push "lock button " on fob#1 once and release
2.turn key off
3.turn key just to the "on" position (not starting)and push "lock button " on fob#1 once and release
4.turn key off
5.turn key just to the "on" position (not starting)and push "lock button " on fob#1 once and release
6turn key off
7.turn key just to the "on" position (not starting) and push "lock button " on fob#1 twice (if you only have one fob, then stop here and go to step 8)and push the "lock button" on fob#2 twice.
8.turn key off and remove key from ignition.
if you did it right, remotes' should work again.
good luck

First thing, does the red light on the remote light up when you push any of the button
if no, then replace battery inside remote
if yes, then try repograming the remote to the car again.
-Have both remote ready. fob#1 and fob#2 (doesn't matter which one is #1 or #2)
-each step has to be done within 5 sec or it will not work, but don't do it super fast.
1.turn key just to the "on" position (not starting) and push "lock button " on fob#1 once and release
2.turn key off
3.turn key just to the "on" position (not starting)and push "lock button " on fob#1 once and release
4.turn key off
5.turn key just to the "on" position (not starting)and push "lock button " on fob#1 once and release
6turn key off
7.turn key just to the "on" position (not starting) and push "lock button " on fob#1 twice (if you only have one fob, then stop here and go to step 7)and push the "lock button" on fob#2 twice.
8.turn key off and remove key from ignition.
if you did it right, remotes should work again.
good luck

Insert key into door barrel or ignition lock and turn key, whilst doing this press the unlock/lock button, the led on the dash should flash to indicate this has initialised the key to the car, then remove key and test operation of remote. If this fails then a new remote plus coding to the car by your dealership is needed

I'm more familiar with Range Rovers and Saab's when it comes to key fobs but if you changed the battery you have to re-program the key fob. If you do not have an owner's manual that can take you through the steps you might want to try: push and hold the lock button on the key fob, put it in the driver's side door and turn to lock. With the button still depressed turn back to open, remove the key and release the button. If this doesn't work check any and all fuses associated with your system and last but not least you could take it to a dealer. Good luck!

If it is a 2003 model year vehicle follow this procedure. If it doesn't work, you may have the wrong fob which happens all the time.

Sit in vehicle and close all doors.
COMPLETELY insert and remove ignition key more than six times within 10 seconds.
Hazard lights should flash twice.
Turn ignition to ACC position
Press and hold any button on the new key fob hazard lights will flash twice
For a second key fob using the master lock switch, lock and unlock the doors then hold down any button on the second remote until the hazard lamps flash twice.
Then you are done open the door to exit the programming mode.
If the lamps didn't flash when holding down the key fob make sure you have the right key fob, they are different for each car.