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Discussion Starter · #1 ·
Hiya,

So, this looks like a standard fuse 16 issue at first. I was driving the car on vacation, turned the headlights on (top button, of the left two), and the other lights didn't automatically turn on. Press the lower button, nothing. Press, press, press, nothing. Per the wiring diagram (Color wiring diagram for Elise sheet 7), that's fuse 16, which goes into the switch pack module, and controls side / rear lights, backlight, etc.

So I go into the store to get some fuses (because of course I'm on vacation and the one thing I forgot to stick in the toolbag were fuses), drive the car to a park ... come back to it, and the lights work again.

Parked the car for the night. Possibly relatedly, the alarm goes off. In the morning, those lights don't work again. Headlights always worked.

Drove the car yesterday. Now, when we were on vacation, we stuck a lunch box in the passenger footwell, so we thought maybe we wiggled something there in so doing. I drove the car in order to play with the stuff hanging out there (what looks like a set of two relays, and four fuses.) No dice. Okay. Drove home, halfway through the drive, all the lights came back on.

So, my question, friends: how in the heck do I debug this? I imagine step 1 is to wait for the lights to stop working again. Then replace the fuse, because why not. Then what's next? I am not even sure where this wiring goes, yet, but I'd love some assistance on what to probe to figure out where the break is.
 

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Discussion Starter · #3 · (Edited)
I googled, but I will search better. Thanks.

Edit: This talks about fixing the switch pack module, but not about ascertaining that it is in fact the module before ripping the dash apart to get it out and measure it. Switch Pack Module Repair -- How to I am hoping there's a better way to be sure, because otherwise it's a fairly big job ;) (Edit edit: of course, the advice to swap the buttons is great advice.)
 

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I would start by checking your battery grounds>bulkhead and to engine. If all meters good check your battery voltage should be 12.6 engine off and 14.6 running over idle. I would then have your battery load tested just to make sure it's got all good cells. Auto parts store do for free. You can have 12.6 and still have a bad cell. Our cars are finicky to voltage and grounds so once that has been ruled out. Report what you find and then we can figure some probe points to check if it fails again so you can be reasonably sure of the SP needing replacement rather than just throwing parts at it.
 

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Discussion Starter · #5 ·
Sure, testing the battery voltage and grounds makes plenty of sense. Though TBH I have not yet seen a battery that had a healthy engine-on and engine-off-car-fully-cold voltage, but failed load test. I'll come back when I've checked voltage at grounds, voltage of battery, replaced the relevant fuse just in case, and swapped the switches. I'm also hoping it gets into the "bad" state again because it'll be a lot easier to diagnose that than in "good" state.
 

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2005 Lotus Elise
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Time to drive out the demons.....

Gesture Font Line Musical instrument accessory Thumb
 

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Years ago I had some weird electrical issues right after pressing and unpressing the hazard button. It lasted for about a day and then everything went back to normal on its own. Did you happen to use that button? A number of people have mentioned that it can be flakey.

Recently I let a friend drive and she stopped the car and pressed the hazard button. I had a panicky feeling as I had deliberately avoided using that button for years. Luckily it did not cause any issue.
 

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Discussion Starter · #8 ·
Hmm.... good question. We did use our hazards, but the issue appeared probably a full day and several hundred miles after. I drove home last night using the hazards because the rear lights weren't working; they started working after like 10 miles of driving, and still work now as far as I know.

I guess if I just ........ drive around ... without using hazards ... and this intermittent failure never rears its ugly head, well, I won't really be able to properly debug the issue anyways...
 
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