Getting hot on the highway with the AC on.

Better not let yellowrose see this post ^^^^^

Or anyone else. Sorry, Brian, but you are almost totally wrong. As YR correctly explained early on page 1 of this thread. This stupid urban legend about coolant moving too fast and not giving up its heat is "not even wrong", as Wolfgang Pauli once said. Anyone with the least understanding of thermodynamics, heat transfer and fluid flow would agree.

What you ARE right about is that the a/c pump has fewer blades, but for a completely different reason. The a/c pump stock pulleys have an overdriven ratio (as opposed to the underdrive with the non-a/c pump). That a/c pump is designed to be turned faster so that the fan can be turned faster, thereby providing better cooling at idle and slow speed with the a/c running. It moves about the same amount of coolant as the non-a/c pump since although it has fewer blades it is spinning faster!

That's the last time I'm going to give this speech. Believe what you want - but it's unfair to teach others who may not know better.