electrical and ignition Help needed with #8 fuse burning out

[doslucero]

Every time I turn the lights on on my 76 2002, The #8 fuse breaks.  I know that the #8 goes to the rear right tail light and brake light as well as the instrument cluster lights. Neither the right tail light or instrument cluster has working lights.  I checked the wires going from the tail light to under the dash.  I didn't find any wire that was contacting metal.  I rewrapped the wires to the rear tail light.  I took out the gauge cluster, non of the wires going to the gauge cluster looked fried.  I even replaced the light switch cause it was falling apart.  I also checked the wires going into the fuse box.  I didn't see anything out of the ordinary.  The only other thing that the #8 fuse goes to is the fog lights but I don't have fog lights so nothing is hooked up.  If anyone has any other suggestions, please let me know.  I also checked the ground to the tail lights which is near the left tail light.  I cleaned up the ground.

 

Thanks, 

Roberto 

[Mike Self]

To find the culprit causing a blown fuse, you need to disconnect each circuit on the fuse, one at a time.  When you disconnect the bad circuit, the fuse won't blow again until you reconnect it.   Do this at the fuse box itself, as the problem may be in either the wiring to the load  (light, electric motor etc) or the wiring itself.  Have plenty of spare fuses, as you're gonna blow a few.

 

Once you've isolated the bad circuit, leave it disconnected and do some continuity checks.  Using an ohmmeter (with the circuit still disconnected from the fuse box) see if you have continuity between the wiring and ground.  If you do, there's a short somewhere.  Next, perform the same test with the load on that circuit.  For example, disconnect the tail light bulb socket from its wiring harness, and see if there's continuity between the hot terminal on the tail light bulb holder and ground (bulb removed).  If there is, the bulb socket has a short.  If it's OK, then do the same test with the wire.  If you show continuity between the wire and ground, then there's a short in the wire somewhere.  

 

One final thing:  check the wiring on your fuse #8 with the factory wiring diagram.  I had a similar problem with fuse 11 on my '73.  All the circuits checked out--and then I found an extra wire at the fuse box.  Turned out to be the seat belt warning light circuit:  one of the seat sensors was shorting out.  And that circuit wasn't shown in the factory shop manual!  Dunno if that may be the problem on your '76, but it's worth a look.

 

cheers and happy troubleshooting

 

mike

[Simeon]

As a further tip to go with Mike's is to replace the fuse with a bulb wired across the fuse holder. This will light up with the current flowing through your short. This will save you some fuses as you work through the circuits powered from the fuse. When you have found your short and cleared it the bulb will go out. 

 

Here is is a good post on the subject

 

http://www.dsmtuners.com/threads/finding-a-short-partial-short-or-battery-drain.179481/

[LB72]

I was having similar issues and it happen to be the wiring for the reverse lights, located behind the transmission that was the problem.

[doslucero]

Thanks for the info guys.  I'm going to do some continuity testing today after work on the wires to the rear tail light and the lightbulb socket.  I'll let you know what I find.  I have about 15 extra fuses so hopefully I don't blow all of them before finding out the issue.  Mike: I checked the seatbelt sensor wires.  They aren't hooked up and don't look to be shorting but I'll check those more thoroughly today.  LB72: I recently replaced the reverse light sensor on the transmission and fixed the wires.  I don't believe that is the issue because the backup lights work but I'll get under the car and take a closer look.  Thanks Simeon for the link.  That process seems a little confusing but I'll read it again when I have more time.  Would I be able to do that test with the light tool below?

 

[Simeon]

The test light will do it. 

[doslucero]

Update:  I believe I found the source of the problem.  I took Mikes advise and disconnected each individual wire from fuse #8.  There were two grey/white wires going to #8.  One wire went to the back right tail light.  When I disconnected that one from the fuse.  It still blew.  Then I disconnected the other one and It didn't blow.  So I followed that grey/white wire.  Come to find out, It goes to the front right turn signal.  I had no Idea #8 fuse goes to the right turn signal.  As I followed the wire and got close to the turn signal light, there was a split that was not connected to anything, It has some cobwebs in the split connector.  That could have been an issue.  As I got closer to the turn signal, I couldn't pull the wire out from under where the turn signal light sits.  I think corrosion took its course and that wire was stuck in the right front fender.  I ripped the wire out and replaced it.  I definitely think that wire was hitting something in that fender but I couldn't tell cause when I ripped the wire out, It broke in half.  So I replaced both wires to the right front turn signal, plugged them into the turn signal, plugged the grey/white wire back to the fuse box and the fuse did not blow!!.  The rear right tail light was bright as ever and the gauge lights were bright too!!.  So I messed around with the turn signal and got it to turn on but not blink.  I believe that the turn signal is bad.  I got it from a 2002faq member which is in pretty bad shape but I wont name names.  The connectors on the turn signal that touch the bulb are wonky and don't line up correctly.  The plastic is completely cracked so I'm going to get a new turn signal light.  Thank you guys so much for your help.  

['76mintgrün'02]

Nice!

You might in fact be better off with a different turn signal assembly, but just for grins, try swapping the two wires.

I have read of lights not blinking because the two wires were reversed.

It also needs to be screwed back on the fender to flash, because those screws provide the ground.

Congratulations for finding the problem.

Thank you for reporting back.

Tom

[doslucero]

Hi Tom,

Thanks for the pointers.  I did switch the wires but didn't screw the turn signal back to the fender.  I didn't know the screws provide the ground.  Ill try that tomorrow.  Thanks. 

[dlhoovler]

Do the '76s have the city parking feature, in which placing the turn signal stalk for a left or right turn with the ignition off lights up the parking lights on the respective side of the car? That may explain why the front and rear lights for one side are connected, and perhaps unexpectedly. Maybe all markets didn't include that feature. But I'm just shooting from the hip.

 

And I was gonna suggest as a solution, just buy an early car. No chance of fuse #8 blowing on my early '71... #12fuseproblems  

 

-Dave