Number 6 fuse blowing - C5 owners check this first!

Sea5

CCCUK regional rep
As our C5's are starting to age there are likely to be more electrical problems surfacing. Given what happened to my Corvette, I expect the problem will occur more frequently. I have procrastinated for a long time about sharing these events but a question arose quite recently on this forum, which has spurred me to write this post.
My C5 is a 2001 convertible, auto, Euro spec. The following is my long-winded story (apologies) but this was a massive challenge that took 12 months to resolve. I had the time, as I had recently retired, but the good news is, it may cost you next-to-nothing to repair!!
Returning home from the NEC car show in Nov 2014, I stopped for fuel at Oxford. As I left the garage (in darkness) all my interior lights, front and rear sidelights failed. I traced the problem to fuse 6 in the passenger foot-well fuse-box. All sorted until I got 5 miles down the road and bang - no lights again! I got home to Worthing by using the rear fogs and headlamps and a torch to read my instrument panel. The problem was intermittent but gradually got worse to the point where at night, I used small LED torches inside the rear lights and another taped to the rear number plate. Come June 2016 I'd had enough and the car stayed off the road for a whole year while I tried everything to fix it. I got hold of a workshop manual (essential reading) and searched all the forums especially 'Corvette Forum' in the States. There were lots of clues but nothing related directly to my problem.
Firstly, I cleaned up all the earth points especially G101 left front frame and G102 right front frame and replaced the multi-connector with each wire soldered to a round terminal and bolted to the upright ground pin. This will solve many other issues that will eventually give you grief if not done. Here is a photo of the corrosion in my original connectors:-
View attachment 3524View attachment 3525C5 grounding multi-conn.jpg C5 grounding.01.jpg C5 G101 modified.jpg
OK, so this didn't fix the problem but worth doing. In desperation the front of the car came off (3 times)! I checked all the connection etc but no luck:-
View attachment 3527C5 fuse problem.jpg
Next suggestion was the Multi function light switch. I had it in bits 2 times and did various adjustments to the contacts but no improvement.
View attachment 3529C5 steering column electrics (2).jpg
Time to pull out the instrument panel to check the mini bulbs and circuits:-
View attachment 3528C5 instument pod circuits.jpg
All proved good, another wasted project! Could it be a bad connection in the fuse box itself (where No. 6 fuse resides)? I'd rather not go there but decided it must be checked off the list. Interesting and challenging (especially putting it back together again) but nothing untoward found:-
View attachment 3530C5 IP fusebox.4.jpg
I did then have a go at pulling the main fusebox apart (this is the one in the engine bay) but I gave up when I realised what was involved!
Another obvious culprit was the Headlamp Module (which hides up behind the passenger side wheel arch). Now this is where it gets interesting.
One of the electrical wizards on 'Corvette Forum' described how he built a replacement headlamp module out of relays and things because he couldn't find an OE one for sale. He went on to state what the voltages in and out of the module should be. I was lucky to be given a spare module to work with (they are like hen's teeth to find). Whilst checking my voltages I noticed something odd but couldn't explain it. With my meter connected, I got up from under the car and leaned on the drivers side fender (as you do) to scratch my head and ponder 'where do we go from here'? My left hand lent on the headlamp connector and I heard the relay in the module click!!
Going back to another (one of many) posts by the legendary Bill Curlee, I remember him describing a common problem with a similar connector in the passenger door. One of the female sockets (for the bus-cam circuit) was badly formed which meant that after a time, the male pin wouldn't make proper contact. This causes huge issues with the C5 circuitry and possible heart attacks for the owners! Easily fixed when you know where to look.
Sure enough, the sun came out, the birds started singing and I finally got to the root of the problem.
Upon close inspection, one of the female sockets of the five, was miss-formed. This is apparent in both left and right side connectors.There are 5 wires in and out: high beam supply / low beam supply / headlamp up / headlamp down and EARTH. The earth is the black wire and this was the culprit.
View attachment 3531C5 Faulty Headlamp connectors .1.jpg
I have studied the wiring diagrams over and over but I can't explain why this earth wire causes the fuse #6 to blow other than this theory: The high voltage used by the headlamps / motors, cannot go to earth when the circuit is suddenly broken at this point so it seeks another path. Could it be that it finds a path via the sidelight grounding circuit and overloads the sidelight fuse (#6). The headlights and motors are on different (heavier) circuits (and fuses/circuit breakers) and have no other connection to the (lighter) sidelight circuits - except they all ground eventually, at G101 &102. The simple fix was to cut and re-connect the black earth wires outside of this connector. I used a soldered spade connector - not pretty but very effective.
C5 Faulty Headlamp connectors .2.jpg
My problems went away and the lights have not given any issues for the last 2 years.
I'm very grateful for all the information available in the CCCUK and other American based forums, so I hope my experience will help others to solve this complex, yet simple to resolve issue.
Gary White
CCCUK Sussex rep
 
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