Reduce LED Brightness

Resistor is one way.......but LEDs are a DC device.
Why you would need 24v in any case is beyond me as it means large power disipation in the resistors.

Do you have a drawing of your circuit..??
Include as much info as you can.

 

If your panel indicatators are indeed 24V, they are probably AC or DC compatible.
But as @Bluejets already stated, a resistor is one way.
For a 2.8V LED @ 15mA, a 1.5KΩ half watt resistor is required. As we don’t know what resistor is in place now or how bright your liking is, you can add another and reduce or increase the value until you’re satisfied.

Martin

 

And the load being just the LEDs?.
According to the data sheet, the resistor is internal.
And it’s 24VDC.
Kind of OTT for just two LEDs.
So add another series resistor.

Martin

 

On the internet thingy you can buy variable LED dimmers that use PWM. They are mostly made in China (Yuk) and are quite cheap. I have 2 running under cupboard LED strip lights. They can be varied from almost off to full on. Have a look on Ebay or Amazon.
See link below for the sort of thing I am referring to.

12V 24V LED Strip Light Dimmer Switch 8A Voltage Regulator Adjustable Controller | eBay

 

I would use a series resistor. The question is how much (%) brightness do you want? If you want 50% of the current brightness, then as Martaine2005 mentioned, it is probably about 1.5K resistor internal so add a 1.5K 1/2W in series.

Another way to reduce brightness is just put a thin coat of low-medium pigment paint over them.

 

Feeding LEDs with AC may become lethal to them. I would replace your 24VAC supply with a 5V usb (phone) type of wall transformer available at many forgotten drawers and evaluate brightness.

 

^ It is a 24VDC supply, which I would not have chosen, along with not choosing 24V LED modules, but zoom38 already has them, they have integrated resistors (don't know if they can be opened and swapped with a different value resistor), and are fairly expensive for what they are.

If it were something higher powered, I'd be concerned about the wasted power, dropping from 24V to around 2V, but in this case is only 15mA (30mA if both lit simultaneously, except the goal is even less current for less brightness), a fraction of a watt so (depending on regional power cost) it could take decades for equivalent replacement parts more than a resistor added, to pay for themselves in power savings, plus the effort to do so, I mean this must already be installed so putting a resistor in series is as easy as it's going to get.