FWIW ?I did the Heater Core By-Pass Mod with the Ranger valve, but I've found I miss the By=level for Heat in the winter. Bob, at Dieselsite sez they are going to introduce an 12v operated valve, selective in any blend posistion, A/C or Heat.
'Bout 2 weeks ago he said it should be available very Soon.
It depends on which vacuum line you tie into. The red I think will only give you heat on the windshield and in the floor. But if you tie into the white vacuum line behind the glovebox it only cuts the heater core off in the max ac position. Explorers had the valve too. I got mine off a '96 model explorer.