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Discussion Starter · #1 ·
Hello,

I've been enjoying fixing all the little bugs on my 96 Continental. The forum has been excellent! I have a situation with the heater fans whereby they really only go on if I select defrost or facia vents. I hear all the servos running and definitely feel heat coming out but more of a dribble. I understand there's the sensor on the thermostat that signals the coolant temp is sufficient to turn the fans on.

Head Hand Arm White Organism


I understand that a good starting point is to disconnect this switch to trick the system into thinking there's enough heat to trigger the heater fans. Since access to this switch is pretty limited without removing the intercooler, I'm trying to get a sense on what pin on the controller receives this signal. On another forum, I read "left control, pin 1", but that was for an earlier Series.

Since I have the dash and console apart for wood restoration, I was hoping there might be a simple test at this point. I do have access to the workshop manual and wiring diagrams, but nothing is jumping out.
 

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Yes, it is the UE74605 45° sensor (also known as the 44° sensor or switch) which inhibits the operation of the AC until the coolant temperature reaches that temperature. Simply unplug it to isolate it from the system. It is not really a sensor, it is an NC thermostatic switch that opens at 44°C which allows operation of the system.
 

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Discussion Starter · #4 ·
OK, that's what I figured. What I was wondering is since I have a later model the access to the thermostat appears to be pretty brutal, I'm hoping to identify which pin at the hvac microprocessor receives that signal. It may not be that simple, however, If I can remove the pin temporarily I might be able to achieve the same result (i.e. tricking the system to thinking there sufficient heat at the coolant).

I was going to borrow the tester from flying spares, which seems reasonable, however return shipping from the states seems to be VERY expensive, at least it was when I returned an alarm ECU.
 

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The 44° switch controls the inhibit relay and does not go directly to the AC ECU. If you follow the diagnostic process in the workshop manual you can find and rectify pretty well every fault in the system without the test box.
 
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