[whited44]

Right above the pumps is the check valve. Give them a decent whack with the back of a screwdriver and that should free them up. Can you tell if the AH is actually heating? Are any of the pipes getting hot at the unit itself?

It must be heating because I do get hot water out of the faucet.  I ran it on the diesel side for about a half hour last night and none of the pipes really got that hot though.