my 84 300 SD (w126) has a problem with the rear defogger, it only defrosts the top 1/3 of the rear window. How do you go about diagnosing the problem? The light in the front console comes on and stays on for 10-20 minutes but only top 1/3 gets defrosted. The elements appear intact, but is there anyway to test them?
1) 84 300SD 285K+ Miles (Ver Calif)
2) 84 300SD 175K+ Miles (Ver Federal)