TIL the hard way that thermal paste isn't a suggestion

Back in March I had an LRU in a King Air that kept throwing intermittent temp faults. I figured it was a bad sensor so I replaced it twice, no luck. Then an older tech named Frank came by and asked if I used thermal paste on the heat sink reinstall. I said no, I figured the factory pad was enough. He made me pull it apart and sure enough the pad had cracked from an old repair. It cost me two days of troubleshooting and a red face in front of the pilot. Now I always keep a tube of paste in my box and never trust a used pad. Has anyone else had a simple material fix a weird avionics gremlin like that?

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clairec7812d agoOG Member

...and here's the thing nobody talks about, the thermal paste isn't just for heat transfer. It's also a gap filler. Those factory pads look fine on the surface but they compress and harden over time, especially in a vibrating bird like a King Air. I've seen intermittent issues in radar units and even a comm transceiver that traced back to micro gaps between the chip and the heat sink. Vibrations make those tiny air pockets shift around, so you get a temp spike only when the plane hits certain frequencies. Frank saved you a world of pain, that red face is nothing compared to pulling a whole panel to chase a phantom that was just a pencil-thin void the whole time.