[Matthew_Murdoch]

I have this problem, during the day police sirens lights don't show but during the night they do.

Is there a fix for this problem?

[Austin_Lynn]

No, it is because of the lighting from the weather, nothing you can do to fix it, sometimes they work, sometimes they don't.
If it is a mod, then try to find anther one.

[ExoSanty]

Seems to be normal:

http://forum.sa-mp.com/index.php?topic=128392.0