Amp meter wiring / instrument gauge issues

[Crocha617]

So I challenger convertible I bought a few months ago has some electrical issues. The gauges work sometimes and sometimes they don't. It's not consistent they would all work and then sometimes the oil pressure gauge would go out. Sometimes the oil and fuel gauge will go out. Recently all the gauges including the tach stopped. Yesterday I pulled the switch panel and cleaned up the dimmer and noticed the lower left screw was missing which I believe grounds it. I replaced that and the gauges still didn't work so as it was running I was playing with wires behind the gauges and apparently the amp meter gauge wires were loose I heard some sparking and the car stalled. The main fuse under the hood blew out. This is how the amp meter was wired I'm assuming it grounded against the gauge cluster or something. Any one ever seen one wired like this? Not sure why the jumper wire is there or where the red with black stripe wire is going. I will investigate this afternoon. Put in a new fuse and it blew instantly so there's definately an issue....

[Crocha617]

Heres the picture

[dodj]

That's one way of jumpering the ammeter. But a poor one. If your ammeter is out of service anyway, take both ammeter wires and bolt/tape together. The other red (smaller) wire is just where some previous owner decided to get power for some accessory.
What fuse is blowing? The fuse link in the engine compartment?

[Mr Lee]

Hmm not my area of expertise but I can put in two cents from experience..    you are correct that a lot of things on these cars ground to the body, so it's helpful to make sure the paint is sanded off where your screws attach electrical equipment to the car.  And a little dielectric grease wouldn't hurt to help keep it from rusting.

Yup, that amp gauge wire could've grounded against the housing.  Look really closely at where the wires are held onto those studs on the back of the gauge housing.  The paper washer may not be covering the gauge housing as well as it should, all the way around the stud, and the little nut and washer can touch the housing.  Same thing happened to me and my dash started to smoke. 
   

Yeah that jumper wire is probably there to bypass the ammeter but it's not enough just to bypass the ammeter.   I don't know if this is the cause of what your experiencing, but that bulkhead connector in the firewall can act as a restriction point for current flow and cause things to melt and fry.  There's been a lot of discussion on this.
http://madelectrical.com/electricaltech/amp-gauges.shtml

You can install a volt gauge in place of the ammeter.
https://forum.e-bodies.org/interior/6/voltage-gauge-for-cuda-rallye-dash/685/

[Crocha617]

The extra red wire is for the power top. I wasn't thinking clearly earlier. I'm going out to mess with it now. I'll keep you posted. Hopefully I can get it figured out today. I finally have some time to drive this thing after a crazy busy summer and this happens.

[73chalngr]

There is a volt limiter for the small gauges .  RTE makes a solid state one to replace the old style one . The small gauges work on a lower voltage and I believe the old style clicks open and closed to reduce the voltage .

[Crocha617]

I disconnected the amp meter and it's working now. Amp meter must be fried... at least its running again. I'll fix it over the winter.