Join Date: Sep 2006
Location: Las Vegas, Nevada
That wire is the auto climate temperature control heater lock out wire, it goes to a sensor on the coolant tube hardline behind the intake manifold between the two cylinder heads, but only on semi-automatic temperature climate control units.
If you have 3 knobs on your ac head unit that wire is unused, all thunderbirds are pre-wired for that connection. However, if you have a 2 dial ac head unit with a digital temperature read out then that wire is used to prevent cold air from blowing out of the vents ONLY when the heat is selected AND ONLY when the fan speed setting is in the AUTO position.
This "feature" is only used in an example similar to this: It's 20 degrees outside, the car has been sitting outside all night. Turn the car on, select AUTO for fan speed, select vent position, select desired heat ex: 80 degrees. No air will blow from the vents until the coolant is hot enough to warm the 20 degree air to your desired 80 degrees. However, this feature is immediately bypassed by not selecting the AUTO fan speed. If you turn it to anything other then AUTO then cold air will blow out of the vents and continuously work it's way up to the desired/commanded temperature.
So in short answer if you have semi-automatic climate control in your MN12 the purpose of "that wire" is to keep cold air from blowing out of the vents until it has the ability to when used in the auto position. In all other fan speed positions, and MN12's with standard climate control that wire does nothing.
-1996 Pearl White Thunderbird 4.6 Sport 4v with many mods:
Current Best: 13.583 @ 103.74 10/2014.
227hp/241tq measured on calibrated mustang dyno, tested at full vehicle simulation with inertia enabled, no number skewing.
-2001 White Ford F-250 Super Duty 6.8 V10, 4-door, 4x4, Limo Tint, BFG KO2's, Bilstein 7100 Remote Reservoir Race Bypass Shocks, 6" Spring lift, Kenwood Double Din, K&N Intake, FlowMaster Exhaust
Amber_Murder's Daily Driver.
-2005 White GMC Sierra 3500 6.6 Duramax, Dually, 4-door, 4x4, Limo Tint, BFG Commercial T/A's, Rancho RS9000XL Shocks, Kenwood Double Din, K&N Intake, Banks Monster Exhaust
Chris_Murder's Daily Driver.