blower goes out on 2000 ford econoline van 4.2L E-150 during acceleration
I'm willing to bet that the fan doesn't stop but is diverted to the Defrost mode. There is a vacuum line that runs from or near the intake manifold to the right front of the van. It has a "T" that connects to a check valve and a vacuum reservoir. Either the check valve isn't holding or the vacuum reservoir is leaking. It's designed to keep the AC wherever you set it during hill climbing or hard acceleration.
Search Ford Econoline Wagon Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Ford Econoline Wagon Experts