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shelbyone

No 6 FUSE

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hi there...every day something new....master brake cylinder, tires, new fuel line...and I should really ask you this....

my no 6 fuse ( breaklights, int. lights) went out about 6 times in the last 2 years..I cant seem to find a short...anyone has the same issue<?

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I don't have my service manual anymore so I can't trace the wires from that fuse. But....if the brake lights are on it then one trouble spot to look at is the third brake light on the tonneau cover. Those lights seem to give a lot of trouble from the wire connectors being riveted on and the rivets coming loose. Haven't heard of those connections blowing a fuse but if the wire routing gets pinched by the tonneau cover you might see a blown fuse. Just in case you ever need to get to the inside of the third brake light you have to open the tonneau cover to get to the two little screws that attach the light to the trim, they are hidden under the weatherstrip. Don't resort to checking inside that light until someone with a wire diagram chimes in.

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The 1989 and the 90-91 models have a number of differences in there electrical systems. The list of items for fuse number six from page 8W-6 of the blue service manual list: "Stop, Under Hood, Bin, Illuminated Entry, Courtesy, Vanity Mirror, Lamps; Power Mirror Motors, And Speed Control". A melted wire on the under hood is a common problem. It can be unplugged near the brake assembly. Otherwise I would go through the list and look for anything that does not work including the lights for the exterior door locks.

-Rich

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Looking at the list from The Lanes, I would unplug that curly underhood wire for the light under there. If the cigar lighter is on that fuse, I would unplug that wire as well.

David in Riverside without a TC anymore.

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It's most likely the hood lamp wire pinched through in the coily portion and shorting out to the body. Follow the Lane's suggestion by simply unplugging it and see what happens.

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I know that this will probably garnish a couple of comments, but I had a similar problem, years ago, in another car until I checked the manual. I found out that someone previously had changed the fuse with a smaller rated one. Yours should be a 20A yellow fuse. Maybe worth a look.

The only other comment I could offer is to check grounds, often a loose ground, with sufficient current flowing at a given time, will cause the fuse to pop. The time that your fuse blows could be rare times when you are using this circuit heavily, unknowingly.

Good luck.

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hey there again...after disconnecting the curyl underhood wire, all was good...for a couple of weeks,,,now the no 6 fuse always blows as soon as I step on the brake pedal...

any ideas now?

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Well at least you know it's related to the brake light circuit.

Since the brake lights are only at the rear of the car that pretty much leaves out a wiring issue in the front end of the car. The first thing I'd check is the turn signals and the emergency flashers to see if they work properly and light both bulbs in each tail lamp. If they work OK the it's a strong likelihood that the taillamp / turn signal wiring is OK. That leaves the brake light switch and wiring at the pedal assembly and the center high stoplight and it's related wiring. Since this lamp is mounted to the tonneau cover the wiring could be at fault or there could be a short within the lamp housing. It's simple to remove once you peel back the rubber weatherstrip under the edge of the cover to expose the screws. There may be a connector that will allow you to unlug the CHMSL but my car's not handy so you'll have to look around in the top storage well to see what you may find.

If you blow a fuse on the turn signals or with the emergency flashers the I'd suspect a problem in the wiring leading to the tailights. The brake light wiring does pass through the turn signal switch as the turn signal flasher interrupts the brake light feed through the switch, but I'd suspect this area last and only after I checked the other stuff first.

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hey george and thank you for your input!...while I was working on the problem, something weird happened: even with the 20 amp fuse not present, the vanity mirrow lights came on..and when I pressed the brake pedal, they dimmed down ...I disconnected the cables that lead to the 3rd taillight..and did not attempt another try..

what can possibly break in a brake switch? I checked that too and it seems fine from the outside..

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You do want to check the turn signals and emergency flashers before going much further. You need to insure that these are working as they should and that BOTH bulbs in each tail light are working correctly for both running lights and for turn signals.

Sometimes these "odd" problems can be caused by something as simple as a broken lamp filament that internally shorts over to the other filament in dual filament bulbs. Get the easy checks out of the way first before trying to trobleshoot the obscure problems. There may be a couple of things going on electrically speaking. If you have a bad or missing fuse unrelated circuits can be back fed through other electrical components. First thing I would do is to check all the fuses in the car. Both those in the interior fuse block and those under the hood. Make sure they're all present and not blown. Then, without stepping on the brake, test every light, and every accessory to see if they're operating as they should. This would include the exterior lights front and rear, the forgotten spare tire compartment light, the rear view vanity mirror lights, the map lights, ashtray and console lights, etc. etc. and even the key in ignition light that has the delay off timer. There's also LED lights in each door lock cylinder keyhole that are tied into the interior light circuit and door handle switch, but have their own delay. Anyting that's not working should be noted and corrected as you go along if at all possible.

Almost all of these head scratching electrical gremlins are usually a simple fix once you find them !

Another possibility could be the various grounds throughout the car. There could be a loose ground or a corroded ground. There are grounding points at various locations on the body. I know a number of the interior circuits are grounded up behind the dash on the door hinge pillars up above the kick panels. Look for a threaded stud with a number of black wires attached. There are grounds on both the drivers and passenger sides.

A service manual would be a big help if you can get your hands on one. The electical diagrams are relatively easy to follow but typically go back and forth between several pages.

If you've had any interior electrical work done or have had the dash out for an a/c system repair or a stereo system swap that may be an indicator of where to start looking. Before you do anything though get the fuses back in.

Another possibility, but more remote and way more difficult to find, would be two unrelated wires somehow shorted or connected together that shouldn't be. Like maybe a wire pinched under a bracket or fastener, two wires melted together or possibly a wire that's been penetrated by a screw. Had any repair or modifications been done to the car prior to this problem ?

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thanks again for the fast reply...in early february, my brakes failed - the master cylinder had to be replaced..also, the corresponding fuse in the engine compartment was fried (where the 3 relays are..all replaced..) I will check the functionality of all the lights and turn signals tomorrow...and let you know..I looked under the dash to see if there is anything wrong towards the brake switch which has not been changed...I did not take it out but it looks good so far...

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