Here's a very simple example:

A -> B -> C -> Z

c(A, B) = 1 c(B, C) = 2 c(C, Z) = 3

h(Z) = 0 h(C) = 0 h(B) = 0 h(A) = 2

All the heuristics are underestimates of their actual distance to Z, therefor h is admissable.

However, h(A) = 2 > c(A, B) + h(B) = 1

Therefor, h is not consistent