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Stock gauge tech

dyeager535

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Writing this just as much so I don't forget as it is for others.

Just got done spraying the inside of the cluster housing and back of the black plastic piece with chrome paint. Looks nice and bright, but there were three dead bulbs before anyways. :)

Swapped my stockpile of gauges (not speedometers) into the cluster, and out of maybe 10 gauges, 2 were bad. They had physical damage, bent piece that the needle rides on, so it's to be expected.

Out of those 10 gauges, 2 had bad resistors. Both were on temp gauges. Temp went to just over 260*, and stayed there, with the engine around 195*. Swapped resistor with known good of the right color, and they worked correctly.

Played around with the various gauges, found out a few facts.

The hand written numbers on the back of most gauges apparently indicates the resistor used. Regardless of which gauge it is, for example, if both say "2", they both use the same resistor. The number correlates to a color. Highest number I saw was 5, lowest 2. Number 1 resistor *might* be unmarked, as I have two that were like that.

Gauges could be tested by stealing the resistor off of one of the other gauges that is working correctly, and swapping it. If the reading changes (although incorrect) it is probably the resistor.

Both resistors that were bad failed a continuity test. All good ones passed. Makes sense.

It is very obvious that these gauges are "tuned" from the factory. Putting the wrong resistor on the volt gauge turned a 12V reading to 15V.

As tough as it is to get to the resistors, it's probably a better idea to simply grab a whole other gauge, unless someone has a cheap source for the resistors.
 
You probably could, but they are a different setup. It's a flat piece of ceramic about 1" long that has the contacts/resistor stuff embedded in it. It has holes that allow it to slip over two of the studs on the back of the gauge, then a nut on each stud to hold it in place/make positive contact. Those studs are then what make contact with the printed circuit board.
 

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