Brake Lights/dash lights intermittent

[Logan Robb]

Uh Oh! Took the 64 out for dinner tonight and on the way home after dark, I noticed the dash lights went out. Not being all that familiar with the wiring schematic, I figured I’d better check the break lights/running lights as well. To my dismay, no brake lights, no running lights, no plate lights. Uh Oh!

Good news is we were not far from home. On the way home, everything came back on. This is the first time of this issue that I know of. My initial guess of fuse is not correct I suppose. So to the garage she goes. 

I am wonder where to start? Ground? Broken wire? Headlight switch? 

Thanks all! 

[Logan Robb]

I should provide an update about what I have found. 

First, here is everything that was completed:

• Significant testing of the headlight switch including jigglings, pulling in and out, rotating many times, spraying contact cleaner as best I could into the switch
  • In doing this, never once did the tail lights so much as flicker off (I performed this test while the tail lights were working)
  • This pretty much confirmed, in my opinion, and before I had the technical knowledge of those that have chimed in since the start of this thread, that the headlight switch was not the issue. A bonus of this testing is the headlight switch operates much better now. 
• Cleaned the one ground I could see off-hand without looking too hard
  • Ultimately, I don't think this solved anything, but it made me feel better. 
  • I'll be consulting the Help Page soon to find the rest of the grounds just to make sure they are all clean for the foreseeable future
• Cleaned the brake switch
  • Again, I don't think this did anything, but it made me feel better
  • It seems to be functioning just as it should, so no issues there

And finally, what solved my issue:

• Cleaned the fuse clips for the stop and tail lamps. 

Yes, yes, yes, I know. I should have done this first. But I am about 6'4" and getting wedged in there and turned upside down is no small feat for a large person such as myself with rather broad shoulders and, for all intents and purposes, nubs for hands. So this one one of the first places I checked, decided everything looks fine, no apparently blown fuses or melted wires, and promptly un-contorted myself from the footwell of the driver's seat and moved on to all the things above. None of which fixed my issue with any degree of certainty. Keep in mind, the way the fuse box sits in my car, or maybe the way the lower dash cover sits, it nearly covered the stop and tail lamps fuse. Even on my initial inspection-I did not see this fuse. 

Finally, at my wits end, I re-stuffed myself into the driver's foot compartment again, this time with a short stool positioned under my rear end to help support myself, and decided I would pull all the fuses one at a time, visually inspect, clean the clips and pray that fixed my issues.

Lo and behold, I had managed to compact myself just far enough in that I noticed one final fuse that I had not checked the last time. The stop and tail lamp fuse. TA-DAH!

The fuse was not blown, however, I did break the fuse trying to get it out, so it needed replacing anyway. 

I took the time and scratched and cleaned the clips as best I could, shot some contact cleaner in there, installed a new 25A fuse, and promptly said some comforting words to the Cadillac Gods that this was my issue. 

I can't say with any real degree of certainty that this was the source of the issue, however, I can say since doing this cleaning of the clips, I have not experienced any issues with the tail lamps/dash lights, stop lights, or any other lamps and I have not been able to replicate the issue. 

So, there ya have it. It seems all who suggested the fuse box were right.

The lesson here is to be 110% thorough with your inspections. I ALMOST took the dash off to clean and inspect the headlight switch. While I am sure this would certainly not hurt anything, I was NOT looking to do that right now. 

Thank you, thank you, thank you to all who commented and offered your advice on this issue. The amount of knowledge present in this forum is absolutely astounding and I do not take it for granted one bit. I am beyond thankful to be a part of this community and hope to suck up as much knowledge as I can to someday, hopefully, return the favor!

TL;DR

Check your fuse panel. It seems dirty/corroded clips on the nearly hidden stop and tail lamp fuse were the primary issue causing my brake lights to not function at all. 

Logan

[Jason Edge]

Congrats on the find. I would clean all the fuse clips in same manner if you have not already done so.  The lesson here has been not to guess what lights or other electrical components are on what circuit but to check the shop manual.   As I had noted earlier the Tail & Stop lights, Ash Tray lights, cornering lights, courtesy lights, ignition switch lights, and instrument cluster lights are all fed from Tail and Stop Lights fuse, not the Body Feed Fuse.  That is your clue which is what Mark and others reiterated.  If it had been simply jiggling the headlight switch to get the instrument cluster lights on (which was a problem I had had in the past) then that would be your clue, but you were dropping lights all fed from that fuse.

Just to take this a step further, when I part a car out I see that brown oxidation and rusting on the those clips as I always remove the fuses and circuit breakers.  I took an otherwise excellent looking dash harness out of the last parts car a couple days ago and when I started removing the fused there was a fine coating of rust on all the clips.

The other place I see this is on the bulb base contacts. Those dash instrument cluster lights are bad for getting rust residue over the years. If you have access to them (i.e. dash pad off) take and clean the ones you have easy access to by doing the same thing you did --> scraping off the rust layer and cleaning. I also pull the tabs inward a bit to make sure they are tight against the bulb when you put it back in.  

[Logan Robb]

I have been enjoying the light-Yes! Thanks for your knowledge and insight as well!

Logan