OK, I tried to replace the turn signal and marker bulbs on the front passenger side of my '99 Disco 2. I followed the directions in the manual, used the recommended Sylvania bulbs but it still won't work. The fixture was filled halfway up with water and there is some corrosion on the electrical connections. Is that the problem?

Also, I have been told to put the Rotella 15/40 (Diesel oil) in the truck. Is that OK? I guess it was recommended because it is thicker and helps prevent leaking? That is what is in it now and it seems fine.

Any info is appreciated.

 

I run that in summer months and 5w40 winter. Fine fo me.
With water on connection it is likely to have much corrosion that will hinder a good connection. I'd first use a small wire brush and pick, to get good and clean. Then test the connection. It does not take a lot of build up to insulate the connector

 

Thanks for the response!

 

I use Rotella 5w-40 all year.
The water is your problem, the bulb socket needs cleaning or replacing.
The seal is bad on the lens, either replace the lens or drill 4 small holes, two at the bottom and two at the top, on the edges near the corners, this will allow for ventilation but will not let water in.