378TS day running light issue with lamp replacement

[Nomore9-5]

Some of this may be a lack of not understanding how automotive elect systems work but I'm stuck. One D/L lamp went out .I bought a new one .Replacement didn't work but works on other side. I tested the socket harness and got 12v .I bought 2nd harness, thinking lamp connection might be weak .I put tester probes back into original socket to determine which wires to pair up to new harness. I plugged in new lamp into new harness and took bared end of new harness wires and made alternate contact with tester probes still in old socket. Not only did lamp not light but the 12v I had at socket went down to 0.

Can anyone help me out here I half expected if I had 12v replacement lamp would work in one of the 2 positions

[abjb]

If you have 12V on the socket but the lamp doesn't work then you probably have a broke/loose ground.

Take a look at this thread, note post #'s 3 and 7.
http://www.forestriverforums.com/for...ers-44474.html

ab&jb

[Nomore9-5]

Thanks for clearlng ( hopefully ) thinks up. Will have a good 2nd look tomorrow morning when there's better light but it looks like both ground and positive wires lead back to a real rats nest. If I can't sort things out I might just splice a dedicated ground wire from the socket harness to frame .Thread that you sent was a nice touch

Thanks again