Low pressure switch/Casper's repro harness


New Member
Mar 12, 2023
So, I'm trying to revive an old hot-air-to-cold-air project. Complete '86 drivetrain w accessories into an '84 T-type. Pass fender is off and Casper's harness is going in but I noticed lt.blue missing in 4-pin HVAC feed plug which lives between heater box and firewall. Diagrams I've been able to find seem to indicate that this is is in-line with the boost/low refrigerant A/C cutout relay and seems to me if I don't modify something the compressor clutch won't engage. Whatever it is, this switch is "normally open" so it stands to reason that if its -permanently- open due to not being connected to anything something's not gonna work, right? Am I overthinking this!? Guys at Casper's are great but seem to think it's a non-issue.

Also, interested in anything else I should be looking for wiring or vacuum-related here!

That’s power, ground, and pressure switch for the hvac I think you’ll need it.