I heard you could put in an instument cluster from an EX onto a dx and it would work totally plug and play. I thought it was wierd but i got one and it worked. I was stoked. and it worked for a long while. Recently though it seems it goes out sometimes. It doesn't just not work instead it only revs up to like 3k. The engine revs plenty higher but the tach slows down at about 2.5k and stops around 3-3.5k.
Any ideas? is this a simple fix or not worth my time?

 

the tachometer probably needs to be replaced