New wiring harness in 62 CJ5 leads to gauge problems

Okay, so the new wiring harness in my 62CJ5 is all installed, but that's when the problems began.

The system was converted to 12 volt and generator replaced with an alternator long before I got it.

I connected the fuel and temp gauges in my aftermarket speedometer cluster, turned the key and both promptly began to smoke and burn up. I connected the dimmer switch for the lights with the same results. I then tried a second fuel gauge that I had lying around the garage from an old cluster with the same result.

I now have new gauges and a new dimmer switch, plus the original horn I want to re-install but before I do I want to figure out what I did wrong the first time.

The gauges I used were advertised as "12 volt gauges." So, I'm wondering if one of two things is possible:

1. I wasn't careful about making sure that the electrical connections on the back of the gauges were not touching the metal housing on the speedo cluster and thus shorted them out. But that doesn't explain the dimmer switch.

2. There is some sort of resistor required in the system to make up for the power fluctuations from the alternator.

Other ideas?

Everything else electrical is working properly; turn signals and indicators on the gauge, lights, etc.

I am about as familiar with electricity as fish are with space travel, so I might just be in way over my head here. Any ideas of what to check next would be appreciated.

 

Your original horn may not last very long on 12V.

Your dimmer switch should not have smoked. You probably have a dead short in the headlight wiring such as a high or low beam wire shorted to ground. The dimmer is not voltage sensitive.

If your wires on the back of the gauges were shorted to the speedo case then you would have burned the wires not the gauges. The original fuel gauge was designed for 6V and will burn up when 12V is applied.

The alternator has a diode (rectifier) bridge that automatically filters any output fluctuations. There is no resistor or resistor wire in the alternator output. This would defeat the output power.

Your new gauges may not have had a built in voltage regulator and an external one was required. Not all suppliers will tell you this.