Even if you had easy access to it or could remove the matrix to work on it, I doubt that you'd ever get it good enough and would quite probably tear the annealed copper that it is.
So,it's out with the Haynes manual and find a replacement from a scrapyard, main dealer or online.
The car is a Mitsubishi Pajero (Shogun). The matrix is hidden behind 10 hours of dismantling all of the dash, the instruments and all the controls from gear stick to compass, levers, wires and spring loaded booby traps. Then there is the repair/re-new work and then the fun of putting the jigsaw back together.
When they build these cars they put the matrix in first then......
I have joined the two rubber pipes together for now, bypassing the matrix. I get to use the car but freeze my n*ts off.
Still, summer is just around the corner. Isn't it?