[COE Dan]

Dirty Dan,

I am using stock gauges in my 47 COE with 12V negative grounded power on a 59A flathead. They work correctly and I am using the Runtz voltage regulators across each guage.

First, did you convert your 36 from 6V neg ground to 12V positive ground? If so, you may have your circuits backwards.

Second, see my attached schematic - top half (bottom half is a separate circuit). This is how I hooked up the power to the gauges. The wire to the sensors on each gauge is the stock method.

Ammeter: Your new 75A alternator will not be pushing 75A to the circuits. Voltage throughout the system will always be 12V but accessories only draw as much power as they need. (i.e. a 1 amp bulb will only draw about 1 amp). So, you can use your old ammeter. If you ever draw 75A or see a full scale deflection you probably have a short. Also, 12V accessories take half the amperage to do the same work so you may not notice dramatic changes to your ammeter readings. I'm using the stock ammeter but I am running a 12V generator which has much lower output than your alternator. I've had no issues.

Fuel gauge: My fuel gauge is not connected. The original tank has been removed and an aftermarket tank installed. The original sender will not install in the new tank but the new tank has a sight gauge installed and I don't need the original.

Temp gauge: Works fine using stock sensors.

Oil Pressure gauge: My oil pressure gauge is the 80lb type. If you use the 80lb gauge, you need to use the 80lb sender. Likewise for the 50lb gauge/sender. They sender and gauges will work with each other but the readings will be off. However, all you really need to know on these flatheads is if you have pressure or not.

Last thing...it is possible you have two bad gauges...

Hope this helps.

COE Dan