What happened???

I no longer have the stock fuse panel so I cant confirm but it sounds like you have a short to ground somewhere in the pink power wire going from the fuse to the guage cluster. The most likely place IMHO would be behind the guage cluster. The short could also be internal in a guage.Looks like its time to break out the old multimeter and get probing.

The guages are just a symptom of the circuit, the problem CAN be there but also any other circuit in the line including the hazard circuit, radiator fan relay etc. I would check from the fuse block out.

Link to Wiring diag from Panteraplace:

Fuse circuit

Pull the wires one at a time from that circuit on the fuseblock and check with a meter for a short. If you can't find it with a meter, replace the fuse and replace the wires one at a time until the fules blows...you just found the problem circuit. Just back trace from there.

Good luck!

Angelo

Thanks guys, what a way to spend fathers day. I did not notice yesterday but the fans are not working either. I've replaced them with the common Fluidyne and sucker fans and a reley for each. Glad I did not have too far to go to get home when they quit, engine did not seem too hot. So you don't think that the ignition switch tumblers took a dive?

Don't think so, the ignition switch is between the battery and the fuse, that fuse would not have blown in my opinion if the problem was the igniotion switch. Since you just changed the fan circuit, I would look there first using the above procedure.

Fathers day chores.....I am working on my car also...trying to put her back together and cool for a drive, hopefully today.

Angelo

Thanks Angelo,

Let me clarify the cooling. I did all the upgrades 5 years ago and have been driving for years w/o any electrical problems. This is probably not related but when I jumped on it I actuall missed 4 gear and I rev'd the engine pretty high, say 5k + then found the gear. It's got a crane roller cam with roller rockers so every thing is fine and I don't have a rev limiter on the MSD. Wonder if I fryed the MSD tac box? Can't work on her now but I'll check later. Thanks again for the diagram, is it for a 74?

...Here's what I know! I'am Looking at the '74L wireing Diagram.

You say the fuse 'Second from the Bottom', Blew.
That would be #11 at 15 amps and is suppose to handle only ONE fan motor(178F).
#12 fuse is 25 amps and carries the current for the second Fan(158F).
If only #11 Blew, and Both fans quit? Perhaps You have Both Fan Motors connected to a 15 amp fuse!? NO way would handle that High of Amperage!!
Also!! The Fuel gauge, AND ALL other gauges receive Current off the #12 fuse!!
#11 delivers to ONE radiator fan, Seatbelt warning System AND the BrakeLights!!
Be Careful!! You don't want to be driving around with NO Brakelights!
DoubleCheck and see if the #12 fuse has also Blown, take it out and TEST It!
I suspect that Your Gearshift into 4th and 'High Rev' may have caused enough of a 'Voltage Spike' to blow a already weakened 15 amp Fuse that was UNdervalue to begin with! I DO NOT believe the Ignition Switch to be the Problem! Because the #11 and #12 fuses are 'Ganged'(at the FuseBlock)and 'SHARE' Two(2)Incoming 12 Volt sources! And the 'Fuse Curcuit' shown above is UseLess!! Nothing is Identified! You must use the Wireing Diagram You will find in the Ford 'Technical Manual'!! Good-Luck with it!...

Marlin you hit the nail on the head. When I went back into the fuse block for a long afternoon I discovered that in fact #12 was blown (just barely). When I checked last night the lighting was not that good in the garage, even with the drop light. I replaced #12 today and all was back to normal, kinda. I had forgot that #11 has always been blown since I got the car years ago. I have one fan relay running from the ignition "on" position wire and the second fan relay from the temp switch in the radiator and to a manual switch if I get nervous about the temp. My break lights work fine but I believe that a previous owner disconnected the seat belt warning system and could be the reason for #11 blowing. The serge as you say when I high rev'd makes sense. Any ideas on the reason for #11 blowing? Must be the way the seat belt warning system was disconnected.

Thanks all