Help! I installed a new set of glow plugs and started right up at 24 degrees. A few days later 48 degrees and took forever to start with a nice white smoke show lol! My glow plug light comes on as it should (no flashing). When I pull a boot from one of the glow plugs and test it, it has 24v and never tapers down like it should. Is this a smart box issue, GPC issue, voltage regulator issue or something else?? TIA!!