I have a gas fireplace with remote...the brand is SIT?? and the remote says transmitter unit 0.584.004...the fireplace is not responding to the remote...what should I do?

It is a mechanical valve, not electronic. If you have a fireplace with an electronic remote, you need a remote for the fireplace not the valve.

https://www.google.com/search?q=SIT+630+Eurosit+propane+gas+valve

make model replacement remote control

is the search query.
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Every time the batteries are changed in the receiver and transmitter the transmitter has to be "re-learned" to the receiver. To do this locate the "learn" button which will look like a tiny hole so you have to stick the end of a pin or a pen in the hole to press the button. Hold the button down until it beeps at you 5 times and release. press the button again and release and then press Any button on the transmitter.
Once the receiver is set into its "learn" function it does not matter what button is pressed on the transmitter because the next signal the receiver picks up will be the frequency it is attached-to.
In order to change the transmitter simply hold the learn button down until it beeps 5 times again which tells us it has wiped out its memory. Then press, release and press the transmitter.

If you want to check if your remote is working and you have a cell phone that takes pictures hold the remote in front of the camera and when you have a pitre of the remote press the button and you see it on the camera if you don't the remote is not working hope this helps (this goes for all remotes ) Tom

Have you found a reote receiver of some sorts. Does it have a brand name or model number?
No reference to remote but here is a user manual.
Vermont Castings RHE32 Homeowner Manual Table Of Contents

http://dl.owneriq.net/f/fca9a6da-10a6-4de4-b260-958c6c719160.pdf

Check the batteries. in the receiver and remote.

To re-sync your Honeywell 8220 transmitter to the valve: Turn the Local/Remote switch on your valve to Local. Then switch it back to Remote. Within 10 seconds of switching it to Remote, you need to press the Flame button on your transmitter. This will re-sync your transmitter to the receiver in the valve. Replacement transmitters and valves are no longer available for this system, they were discontinued by Honeywell and they are completely out of stock. Monessen Hearth Systems (now owns Majestic, Vermont, etc) has a retrofit kit with a new valve, pilot assy, and remote for these old RF units. (expensive, but cheaper than a new fireplace). FYI, aftermarket remotes are NOT compatible with this Honeywell system.

It could be that your transmitter is bad. You may want to try to re-sync the remote to the fireplace. Slide the Remote/Local switch on your valve from remote to local, then back to remote. Within 10 seconds press the flame button on your transmitter. This will establish a new frequency connection between your transmitter and valve. Good luck!

It may need to be re-synchronized:

• Make sure the receiver's slide switch is in the REMOTE position.
• Press and release the LEARN button on the receiver.
• When you hear the "Beep", press and hold the ON or OFF button for about 2 seconds on the transmitter.
• You will then hear a series of beeps that indicate that your new transmitter has been accepted by the receiver.
• If you press the LEARN button on the receiver and you hear no beeps, the receiver is unable to retain any more transmitter codes
(make sure the transmitter battery is properly installed and fully charged).
• To delete all of the transmitter codes on your receiver, press and hold the LEARN button for 10 seconds. Then you will hear a
series of beeps, indicating that the receiver's memory has been cleared.

It could also be dead after 8 years. A new unit can be purchased here: Skytech Remotes. I would even suggest on of the new styles with a built in timer or thermostat.

If you changed the batteries in the receiver (the black box in the fireplace). You should also change the 2-batteries in the hand-held remote. This may sound stupid, but it's not ... be sure all the batteries in the receiver (black box) are all facing the proper direction. Believe me, it's easy to get one turned the wrong direction. Also, make sure that the slide switch is in fact in the remote position. It can be finicky at times. Also, check to make sure that the two wires are still connected firmly at the gas fireplace Control Valve and in the receiver.

• Now, if all of that doesn't solve your problem, the receiver may have lost it's code..
  

When matching security codes, be sure slide button on the receiver is in the REMOTE position; the code will NOT "LEARN" if the slide switch
is in the ON or OFF position. Program the remote receiver to LEARN a new security code by pushing in the LEARN button on the top of the
remote receiver and then pressing the MODE button on the transmitter. A change in the beeping pattern, at the receiver, indicates the
transmitter's code has been programmed into the receiver.

There's a lot to check out and do, but that's how you trouble shoot these remotes.

I have the same problem. The company is out of business DESA Heating. I have been unable to find a solution. FMI bought part of DESA but can't get any help there either. 1-866-328-4537