This is getting anoying. Three months ago I was told my rear right brake and turning light was out so I replaced it. Now just today I found out it went out again. I took it out and it looked much like the first one I replaced. It was all blue inside and the bulb had fracture marks on it. What's the deal? Is it supposed to have that blue stuff and be cracked like that? Could there be a short somewhere or did I just happen to have two bad bulbs?

 

Have you been getting in alot of water lately? And does the bulb fit snug into the socket of your truck. Also is the light assembly fit good and solid into the body of your truck. Sounds like some excessive motion or water or both...
Hope this helps..
BJ 77 F150 Shortbox 4x4 400/C6

 

Check your ground, often a poor ground will have strange effects on lights. Run a new ground line if needed. If you find corrosion inside the wire insulation relace that section completely.

Check the harness under the (truck?) vehicle and check the connector plugs. I live in an area where salt eats everything. If you have any connections that were "twisted" "scotch locked" or just plain repaired in a hurry, fix them. Solder all extra connections made.

Use grease inside all your light sockets. Lithium grease is an excellent choice. NO NOT USE "TUNE UP" GREASE. Even wheel bearing grease works great.

I had an intermittant short that was more annoying so until I had the time to chase it down I installed a circuit breaker instead of a fuse. It was more expensive, but a quick fix. Yes, I finally found the time and found the short.

Good luck.

78 Big Bronco 400
84 Big Bronco 300 I-6
93 SHO

All with working lights!

 

Thanks, I'll check it out further. I just put in another bulb for now and when I get the time all check the ground and stuff. I noticed that the previous owner had spliced some wires on it probably for a cheep trailer lights fix-up. I took those and twisted the remaining wires back together... when I get the time I'll solder them. Yes, I did notice the problem the same day it was raining... I'll check the insulation. The whole light assembly fits snuggly in place, but it could be getting jarred around too (our streets have some potholes here and there). I'll check the ground and get some lubricant. I had to recently fix the wiring on our camper (the dog got ahold of it and ripped it out) which was a little more difficult becuase it didn't follow standard color codes. Thanks for all the tips. I'm probably going to have to fix my fog lights too because I noticed they are shorting as well. Oh well it keeps my schedule full.

Thanks everyone...
Oh yes it is a truck it's a '78 F-150 302 V-8.

 

just a suggestion but IF you rewire it from the fire wall back (or wherever) get yourself some of that 6 or 7 strand double insulated trailer wire, solder all the connections, use heat shrink over that where pratical and/or i silicon around all the soldered ends, then wrap it all up with electrical tape. time consuming but worth it.