Original discussion at...
check your connections - make sure that everything is plugged-in correctly and not backwards - this may cause a "short" and blow out the inverter (this is why we recommend having all work done by a professional)
I have had my gauges installed for close to 2 years now... about 12 months ago they started flickering and changing colors for all of 2 weeks - i then switched my connector from the cig lighter to the headlight like it details in the directions that came with the gauges - and also like our online install guide located at...https://www.celicahobby.com/ubbthreads/thread.f_57137_0_collapsed_2__1.html
Then about 4 months ago, right before I replaced the battery in my Celica, the gauges went completely out... after switching the battery to something that wouldnt die within 10 minutes (engine OFF and radio ON), the gauges worked just like new again...https://www.celicahobby.com/ubbthreads/showflat.php?Number=4821
I'd suggest testing that the connections you have your gauges plugged into is always getting 12v of power and not connected to any sort of dimmer (such as the one in your cig lighter)
UPDATE: the following evening, my gauges went out on me again for a while - I pulled up to a drive-thru window and reached for my wallet, accidentally kicking the enclosure for where the inverter was located at - this cause the gauges to regain power and turn back on.
all the night, I thought it was rather strange, so I kicked that location again and the gauges went out... I had to test this theory a few more times, so On with the "kicking" and it became obvious that it was a short in the connection.
This afternoon, I took a look at my wiring and knowing that it truly was a short... after all this time, a whole years and several months, the problem could have just been solved by a more secure connection.
BTW - If you are not using the correct gauge wire, your electricity wont be able to get to the gauges as it should be. (this is also true for hooking up your sound system - thats why the WATTAGE of power that goes through your battery, to your Subs requires at least "X" GAUGE WIRE)