I would actually advise AGAINST the use of the grease, reason being is its thick enough to insulate the contacts of the lamps and connections enough to create a little heat or at least leave everything in an erratic state. With high voltage ignition its not an issue but at 12 volts a fews ohms drop will really dim a lightbulb.

I would look for bad grounds, pull the connectors, lamp holders and clean them with a wet/dry 600 grit paper and also clean the chassis grounds under the drivers side kick panel and under the dashboard with a 250 grit and tighten the screws good. I had the same issue with mine but it happened not only when cold but when the glow plugs cycled causing my fuel and temp gauges to peg.

I since designed my own LED lighting system for backlighting and indicators using high intensity LEDs and they are not only just as bright but take 1/25'th the current to operate.

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