Just so that we are using the same terms, when you say the primary side of the regulator, you mean the input side, right? The side that gets the 12V through the resistor wire? Then by secondary you mean the output side, where the gauges get 5V?
The regulator is connected to the gauges, and the gauges are a resistive load. When you check continuity, you are talking about checking resistance in Ohms, so from the output of the regulator you have several resistive loads (the gauges) in parallel, running to ground. So, you should get some resistance level when you make that check, and 12 Ohms is certainly not out of the question.
The fact that you are getting a lower resistance from the input side of the regulator to the ground is kind of confusing, but may be possible depending on the design of the voltage regulator. However, if you are powering up the steel housing of the gauge panel with 12V, grounding the gauges, and they work, I think there has to be a short somewhere. Ford wouldn't have powered up the steel housing of the gauge panel.
One other thing that dawned on me was the connector. If I recally correctly '69s have a pretty marginal connector to the circuit board, don't they? I seem to recall that the connector wasn't indexed in place real well, and it might be possible to move it around and potentially short two of the traces on the circuit together. Maybe a ground and an input power? Sure wish I was there to look at this for you, Doug...
Yes, I should be saying the "hot" or "input" side and "load" side referring to the regulator terminals. Wrong terminology can confuse things for sure.
I added a picture of the regulator in the schematic. Not sure if you saw it or not, but it shows the connections to the regulators housing, which is grounded through the PCB. The connections to the housing are not only on the load side, but also the input side. According to the books symbol chart, this is a thermal switch that regulates the voltage. Much like the alternator regulator.
The regulators schematic....
Symbol chart....
As you can see, there is some variance from the books symbols to the actual regulators schematic. The symbol shows it being an external heater where the schematic shows an internal type, but with external "graphics". Not sure if it uses a bi-metal switch or some other type. Being DC it can't be based on cycles.
I certainly wouldn't think the housing would be "live" either, but the heater seems as though it could back feed when I apply voltage to the housing. And if the switch is closed that would complete the circuit making the gauges powered.
I have inspected the entire set-up six ways from Sunday and can not find where a short could occur or IS occurring....other than through the regulator itself. And according to the schematic, that is by design for the heater.
And to FURTHER complicate things, with every gauge disconnected from the PCB, and with them REMOVED from the cluster, I get a continuity reading from every gauges post to its respective housing. As if every gauge is shorted to its housing. This is just not right, and I can find no trace of why it should be shorted (as I said, each gauge has its internal and external "isolator" pad)....yet I still get continuity.
I also thought about the plug-ins indexing, and checked it. You can see in this picture that the connections seem to be squared quite nicely with there respective contact....
When I start looking for the sledgehammer as my next tool.....it's time to walk away and take a break. And that is very much needed right now
