diff --git a/src/cgwthr.cpp b/src/cgwthr.cpp
index 690994f56..d1dbe61d3 100644
--- a/src/cgwthr.cpp
+++ b/src/cgwthr.cpp
@@ -628,8 +628,8 @@ RC DESCOND::dc_CheckFixSolar(
 			else
 			{	float ebn, edh;
 				/*float egl =*/ slASHRAETauModel(sunZen, dc_tauB, dc_tauD, ebn, edh);
-				if (frDiff( ebn, dc_ebnSlrNoon) > .01f
-				  || frDiff( edh, dc_edhSlrNoon) > .01f)
+				if (frDiff( ebn, dc_ebnSlrNoon) > .001f
+				  || frDiff( edh, dc_edhSlrNoon) > .001f)
 					oWarn( "ebn/edh mismatch");
 			}
 #endif
diff --git a/src/solar.cpp b/src/solar.cpp
index 747b9fbb9..9b4965688 100644
--- a/src/solar.cpp
+++ b/src/solar.cpp
@@ -1053,8 +1053,8 @@ static bool slASHRAETauModelInv( // derive tauB/tauD from irradiance
 		// calculate Jacobian
 		double Jbb = 1.0 / tauB + logm * (-0.406 + 0.021 * tauD);
 		double Jbd = logm * (-0.268 + 0.021 * tauB);
-		double Jdb = logm * (+0.205 - 0.190 * tauD);
 		double Jdd = 1.0 / tauD + logm * (-0.080 - 0.190 * tauB);
+		double Jdb = logm * (+0.205 - 0.190 * tauD);
 
 		// solve system {-F} = [J]{dtau} using Cramer's rule
 		double detJ = Jbb * Jdd - Jdb * Jbd;
@@ -2849,7 +2849,7 @@ float ASHRAETauModel(	// ASHRAE "tau" clear sky model
 		double ab,ad;
 		if (options & 1)
 		{	// 2013 form
-			ab = 1.454 - 0.406*tauB - 0.268*tauD - 0.021*tauB*tauD;
+			ab = 1.454 - 0.406*tauB - 0.268*tauD + 0.021*tauB*tauD;
 			ad = 0.507 + 0.205*tauB - 0.080*tauD - 0.190*tauB*tauD;
 		}
 		else