Plastic under transistor
I removed the dimmer switch out of my firebird and replaced it with one out another. I plan on replacing the thermal paste. I noticed there some sort of plastic between the transistor and the heatsink which would seriously affect heat transfer, has anyone else replaced the thermal paste on there's ? Can the plastic be removed or does it need to stay ? I'm thinking the contact between the transistor and the metal heatsink might cause a short but i'm not sure.

 

You need that insulator in this situation. Most likely the heat sink is grounded and the case of that transistor has some voltage on it.
Without that insulator you will create a short. And the screws mounting it cannot create a short either.
You need to use the correct heat transfer paste - it's not dielectric grease.

 

Thanks I figured it was important just wanted to make sure.I also found that it's made of mica, not plastic as I originally thought.

 

Go to your local computer store; Fry's, Micro Center, etc; and get their best heat sink paste.

And definitely leave the mica sheet in there.

 

i replaced the gauge lights with leds and the dimmer switched ended up dying somehow, anyone know where to find a replacement transistor or how to bypass it ?

 

The numbers on that transistor seem to be "house" markings - meaning that the original number was replaced with those numbers that the "house" that made the dimmer unit liked better for their inventory. If it is an NPN type, I would bet nearly anything that a common 2N3055 will work. If PNP, then the number is MJ2955.
https://en.wikipedia.org/wiki/2N3055
https://www.mouser.com%2Fds%2F2%2F68%2F2n3055-1108522.pdf&usg=AOvVaw13Ix33jS1arJH7naYJtZFl
With those metal case transistors - the case IS the collector.

 

Thanks, I just tried both of those transistors but gauge lights still haven't come on, none of my fuses are burnt either. Any idea as to how to bypass the switch all together ?

 

You mean just bypass the dimmer circuit? I don't have a diagram in front of me, but there has to be an input supplying power, and an output to the bulbs.
I will assume that those can be connected together and your dash lights will be at full brightness all the time.

 

I was planning on just bypassing the transitors since they didn't work and using a switch for the dash lights I was hoping they'd come in after crossing the two green wires but nothing happened, seems like this is gonna take a while before I have my gauge lights working again. Thanks for the help anyway.