diff --git a/restoration/source410/BT/HEAT.HPP b/restoration/source410/BT/HEAT.HPP
index 98c88f64..6a5c4819 100644
--- a/restoration/source410/BT/HEAT.HPP
+++ b/restoration/source410/BT/HEAT.HPP
@@ -362,6 +362,16 @@
 
 		~HeatSink();
 
+		//
+		// The cockpit's cooling-loop lamp needs both of these from BT_L4:
+		// whether this sink has coolant, and which sink it is plumbed to
+		// (the loop master, whose Condenser number IS the lamp's frame).
+		//
+		int
+			GetCoolantAvailable() const	{ Check(this); return coolantAvailable; }
+		Subsystem *
+			ResolveCoolingMaster()		{ Check(this); return linkedSinks.Resolve(); }
+
 	//~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 	// Local Data
 	//
@@ -484,6 +494,12 @@
 		void
 			RefrigerationSimulation(Scalar time_slice);
 
+		//
+		// The loop number (1..6) -- the cockpit lamp's image-strip frame.
+		//
+		int
+			GetCondenserNumber() const	{ Check(this); return condenserNumber; }
+
 	protected:
 		int		valveState;
 		int		condenserNumber;
diff --git a/restoration/source410/BT_L4/BTL4GAU2.CPP b/restoration/source410/BT_L4/BTL4GAU2.CPP
index 0a40aadb..aa733730 100644
--- a/restoration/source410/BT_L4/BTL4GAU2.CPP
+++ b/restoration/source410/BT_L4/BTL4GAU2.CPP
@@ -94,6 +94,10 @@
 #	include <projweap.hpp>
 #endif
 
+#if !defined(HEAT_HPP)
+#	include <heat.hpp>
+#endif
+
 #include <stdlib.h>
 
 static const Scalar SeekVoltageXScale   = 230.0f;	// 0x43660000
@@ -293,6 +297,40 @@ static Scalar
 //   (the per-frame sampler Gauge::Update drives -- GAUGE.CPP:569).
 //###########################################################################
 
+//
+// The cooling-loop lamp's frame: the loop number of the Condenser this
+// subsystem's sink is plumbed to, or 0 ("OFF") when it has no coolant,
+// no loop master, or a master that is not a Condenser.
+//
+static int
+	CoolingLoopFrameOf(void *source)
+{
+	Subsystem
+		*subsystem = (Subsystem *)source;
+	if (subsystem == NULL
+	 || !subsystem->IsDerivedFrom(HeatSink::ClassDerivations))
+	{
+		return 0;
+	}
+
+	HeatSink
+		*sink = (HeatSink *)subsystem;
+	if (sink->GetCoolantAvailable() != 1)
+	{
+		return 0;
+	}
+
+	Subsystem
+		*master = sink->ResolveCoolingMaster();
+	if (master == NULL
+	 || !master->IsDerivedFrom(Condenser::ClassDerivations))
+	{
+		return 0;
+	}
+
+	return ((Condenser *)master)->GetCondenserNumber();
+}
+
 //
 // CoolingLoopConnection -- @004c3134 ctor / @004c31a0 sampler (vt 0x518ea8).
 // The binary: when the source subsystem's coolant loop is available
@@ -300,10 +338,12 @@ static Scalar
 // "HeatSink" link == linkedSinks) and shows its Condenser loop number
 // (condenserNumber == the image-strip frame); otherwise 0.
 //
-// INERT STUB: HeatSink::coolantAvailable, HeatSink::linkedSinks and
-// Condenser::condenserNumber are protected with no published accessor or
-// attribute row in source410 (heat.hpp) -- the loop lamp draws frame 0
-// ("OFF") until the heat accessor wave lands.
+// LIVE (5.3.36): heat.hpp now publishes GetCoolantAvailable() /
+// ResolveCoolingMaster() / GetCondenserNumber(), so the lamp follows the
+// binary exactly -- the same shape as PowerSourceConnection below.  A sink
+// with no coolant, no loop master, or a master that is not a Condenser
+// reads frame 0 ("OFF"), which is what the box showed for every panel
+// while this was stubbed.
 //
 class CoolingLoopConnection : public GaugeConnection
 {
@@ -315,7 +355,7 @@ public:
 			{}
 	void Update()								// @004c31a0
 	{
-		*destination = 0;
+		*destination = CoolingLoopFrameOf(source);
 	}
 protected:
 	void	*source;							// @0x10  this[4]