Timjame0719 Posted February 4, 2014 Share Posted February 4, 2014 Ok I tired to search a bit for this in the forums and internet and I just can't find the same situation I have going on to compare. A few weeks ago I noticed the left turn signal (and brake light being the same filament) was flashing fast so I thought I just had a light out. The front left turn signal worked but flashed fast and I had no rear tun signal or brake light. I drove it another day and it came back on. So for the next week and a half it was on and off with no apparent deciding reason. I didn't immediately do anything until finally it went out and never came back on. I checked fuses and bulb, no dice. I hooked up my boat and that turn signal worked just fine (although flashed fast)......this is what was different. Seemed that most with the turn signal being out didn't have a turn signal on their trailer either but I do. I pulled the bulb and socket out and tested the end of the wire plug that plugs into the socket and compared to the other side on brake and turn signal I'm getting half the voltage to it which I'm guessing is why it isn't working. I didn't think the ground is bad as the tail light works on that side, just not the turn or brake. Any ideas on what could be going on? Thanks for any help!! Quote Link to comment Share on other sites More sharing options...
akirby Posted February 4, 2014 Share Posted February 4, 2014 Change the bulbs to be safe and change the CHMSL bulb also - sometimes that one is in the same circuit and causes weird problems elsewhere. Quote Link to comment Share on other sites More sharing options...
Timjame0719 Posted February 4, 2014 Author Share Posted February 4, 2014 Will try thanks. I thought that light worked but will check. Quote Link to comment Share on other sites More sharing options...
Timjame0719 Posted February 4, 2014 Author Share Posted February 4, 2014 I checked and the third brake light works fine so it's still just the left brake light/turn signal. Quote Link to comment Share on other sites More sharing options...
akirby Posted February 4, 2014 Share Posted February 4, 2014 I think mine worked too but it still caused problems. If you can't find anything else I'd replace all of the rear bulbs including the CHMSL even if it looks like it's working. It's cheap troubleshooting and at least you can rule out the bulbs. Quote Link to comment Share on other sites More sharing options...
Timjame0719 Posted February 4, 2014 Author Share Posted February 4, 2014 Ok I will certainly not rule a thing out. It has me stumped. Quote Link to comment Share on other sites More sharing options...
J-150 Posted February 4, 2014 Share Posted February 4, 2014 Go to F150online and read up on the multi-function switch. Sounds like the problem here. Quote Link to comment Share on other sites More sharing options...
akirby Posted February 4, 2014 Share Posted February 4, 2014 I think the problem is the filament can be broken but still makes contact sometimes but with less resistance. That would also explain why it's off and on. I've had the same thing with home lightbulbs. Quote Link to comment Share on other sites More sharing options...
akirby Posted February 4, 2014 Share Posted February 4, 2014 Go to F150online and read up on the multi-function switch. Sounds like the problem here. Would the switch cause a fast flash? Quote Link to comment Share on other sites More sharing options...
Timjame0719 Posted February 4, 2014 Author Share Posted February 4, 2014 I'm not sure but I think if the switch was bad I would still have a brake light and also my trailer turn signal works. Quote Link to comment Share on other sites More sharing options...
J-150 Posted February 6, 2014 Share Posted February 6, 2014 Would the switch cause a fast flash? Yes, this was a common issue in Ford trucks late 90s to early 2000s. I'm not sure if your model year truck would have been using the same switch as the previous models. The turn signals, brake lights etc go through this switch. When it goes bad it replicates the effects of burnt out bulbs. Its located in the steering column. Easy repair for a mechanic. I think I paid a little over $100 when I had mine replaced. Quote Link to comment Share on other sites More sharing options...
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