5th gear blows fuse

[kklein90]

Hey everyone, new member here, so sorry if I'm posting something that has already been answered (though I doubt it )

I just recently bought a 78 spider in good condition. The previous owner said he had it 'rewired', so I'm not sure I'm even dealing with stock connections.

The problem (first of many?) is that when I shift into fifth gear the fuse closest to the center console blows (16A), every time & instantly. This causes my gauges to die (except speedo) as well as the brake lights and courtesy light on the console. I'm assuming I have a bad ground somewhere, but I'm not sure where to start looking. Also, does anyone know what it is about 5th gear that turns something electrical on/off?

Thanks for your help!

Kris

[azruss]

there is nothing particular with 5th gear that would cause a dead short. My suggestion would be to pull up the wood on the console and see if the gear shift is pulling on a wire, like the heater fan hot wire and making it hit a ground.

[kklein90]

Thanks azruss! I'll check that out. I did have the entire center console out this past weekend and I'm pretty sure the fan wires are routed along the side, away from the gear shift lever. I did notice that there are a couple wires that run down through a rubber gasket, forward of the shifter, towards the under carriage, perhaps it's those.

[aj81spider]

If it's fuse A (closest to middle of car) then it could be the wires for the reverse light switch. That is the fuse that controls brake lights and some of the other things you mention going out.

The wires for the reverse light switch would run down into the transmission tunnel.

One note, according to my shop manual on a 78 that should be an 8 amp fuse, not a 16. Check your owner's manual to be sure.

I would go to Brad Artigue's site and download the wiring diagram for a 1978 - it will help immensely in the isolation of the problem.

[majicwrench]

Some of these cars have switches to change things (emmsions) when in 5th gear. But as was said, get wiring diagram. See if any trans switches on that circuit. And good luck.

[aj81spider]

Kieth is right. I went back to look at the 78 wiring diagram, and on another page with the emissions stuff is a "backup/5th gear" switch (powered from the "A" fuse). That could also be the source of your problem.

If it were me I would download the wiring diagram (or PM me and I'll email you one) and start tracing the wiring on that circuit. It looks like there are several places you can disconnect the circuit to determine where the problem might be.

Should be pretty straightforward to find.

[kklein90]

Wow, amazing advice guys! Thanks so much. I've got the wiring diagram and as soon as I learn how to read it I'll start tracking this bugger down.