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rdurh
11-27-2007, 08:52
I parked my 1994 Blazer (6.5L turbo diesel) about two months ago because it was overheating and the power lead from the battery to the distribution strip on the firewall broke off. I’ve taken the dash out to work on the heating/AC and to install a better dash. Before I removed the dash I noticed that the headlights and running lights were operating backwards. That is when the light switch was off the headlights and running lights were on, and when the light switch was on the lights were off. With the dash out I’ve plugged back in all the various switches and checked the grounds under the dash, and I still have the same issue.

I replaced the headlight switch and nothing changed. I checked the continuity of the old switch and with the switch off there is continuity across the power terminal to the headlight terminal. With the switch on there is no continuity between the two terminals. The new switch operated the same way. Took the new switch back to the auto parts store and checked all the switches that they had and same deal. Went to the Chevrolet dealer and checked their switches and the same, with the switch off continuity exists between the power lead and the headlights. With the switch in the on position there is no continuity between the two terminals. I was told this was normal and I’ve no reason to believe otherwise after checking six headlight switches. The parts guy at the Chevrolet dealer indicated that they could fix the problem in their shop but wouldn’t indicate what the issue was so I could fix it myself.

The only thing I can think of that I haven’t checked is the multi-switch in the steering column. Is there anything else that could be an issue?

rustyk
11-27-2007, 20:32
This does sound like a ground connection issue, and since GM didn't make those straightforward, I wish you well...

rdurh
01-26-2008, 12:57
Turned out to be a bad ground. Behind the grille on the passenger side on my truck all the ground wires for the front headlights and running lights all come together in a factory crimp which is then wrapped with tape. The tape had deteriorated and the wires at the crimp had corroded & were breaking. All the wires were 12 gauge with one 12 gauge wire coming off for the "master" ground. I cleaned the wires up, soldered them all together with a 8 gauge "master" ground wire going to a battery ground. I then cleaned the headlight switch up and now everything is back to operating properly.