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Diesel Mechanic Poser
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Discussion Starter #1
Ive searched and found about 80% of the information I need, but I cant match all my conditions to get a solid answer of what my problem might be. So far, my 2 choices are: 1)bad headlight switch, or 2) partially melted ignition hot wire that is shorted to headlights on condition. This is difficult to read in a text-only format, but don’t let that stop you from helping.

Victim: 2005 Excursion Limited; Headlight switch functions (5): Auto, off, parking, on (and with ‘pull to light’ running lights option)

Conditions: (malfunction frequently happens when…)
1) OAT= usually between 85 - 104*F …AND...
2) Key on, engine off (KOEO) with with large block connector (harness) to rotary switch connected to headlight switch in any position.
-sub condition: headlight switch on = headlights stay on and relays behind dash chatter
-sub condition: headlight switch off = headlights flicker and relays behind dash chatter in synch with flashing headlights.
3) Key on, engine running (KOER) with large block connector (harness) to rotary switch connected to headlight switch in any position.
-sub condition: headlight switch on = headlights stay on and relays behind dash chatter
-sub condition: headlight switch off = headlights flicker and relays behind dash chatter in synch with flashing headlights.
Note: small dimmer connector seems to have no effect whether connected or removed
[bottom line: key on and ‘connected’ gives malfunction]

Controls: (never exhibits malfunction when…)
1) OAT= usually between 80 - 104*F (effectively all temps) …AND…
2) Key on, engine off (KOEO) with large block connector to rotary switch removed from headlight switch..
3) Key on, engine running (KOER) with large block connector to rotary switch removed from headlight switch..
4) Key off, engine off with large block connector to rotary switch removed from headlight switch.
5*) Key off, engine off with large block connector to rotary switch connected to headlight switch.
Note: small dimmer connector seems to have no effect whether connected or removed

SPECIAL NOTES: (specific conditions NOT found searching the forum and why I need some more help)
*Key off, engine off with large block connector to rotary switch connected to headlight switch = switch functions normally at all times. Off is off; parking lights activate parking lights only; On activates headlights and all related lights.
!! Both KOEO and KOER with large block connector to rotary switch connected to headlight switch; relays behind dash sometimes chatter.
-Hazard light switch punched dozens and dozens of times to ‘self clean’ with negative results.
-Small dimmer connector seems to have no effect whether connected or removed

Diagnosis:
MURDER!! :D (well, not exactly….)
Im leaning to a bad switch from what I have searched for and found. Problem is, the behavior of the connected switch when the key is off is confusing me. When the ignition hot wire is, well, cold, the switch behaves perfectly – even just seconds after a malfunction with ignition hot. This is important. Im not sure how, but its important.

I think I covered all the possible combinations. If I missed one, let me know. So, what do you think? Do I have an intermittent short to ignition hot or a bad switch? Lets hear your diagnoses before I start crawling through rattlesnake infested junkyards. And don’t let me color your opinion or limit it to just 2 things…..
Thanks!
 

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Premium Member
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19,111 Posts
Wow, that's quite the exhaustive list of combinations. Unfortunately, I only have an XLT package, so mine is a very straightforward setup, so I'm afraid I won't be much help. Here's a bump for you, though.
 

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Diesel Mechanic Poser
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136 Posts
Discussion Starter #3
Youre right, that is alot to digest. Im going to see if I can scan or re-make my test matrix and post it.
 

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Diesel Mechanic Poser
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136 Posts
Discussion Starter #4
Okay, here is a troubleshooting matrix that basically shows what I describe above in a very streamlined format. Please refer to the text above for additional information and much greater detail.

The next time it acts up Ill have to test the accessory circuit and post the results.

Thanks in advance for your ideas.
 

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does ford still use the automatic breaker in the headlight switch? if so they can, and do go bad and blink randomly
 

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Diesel Mechanic Poser
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136 Posts
Discussion Starter #6
I havent forgotten about this; it just hasnt happened lately.
Has anyone thought about this lately?
Thanks.
PS. I know - if it aint broke (any more) ...... but Id still like ideas.
 
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