Check the resistance of the coil primary (the small terminals). There shouuld be a measurably lower resistance on the coils without the built-in resistor. I'm prejudiced against internal-resistor coils- - - -they can result in a hard start situation because of limited primary current under some conditions. Wiring up a ballast resistor and a bypass circuit isn't brain surgery, and untold millions of point-type GM vehicles used that system for a long time. If it wasn't necessary, would GM have spent the time and money to equip all their cars and trucks with the system?

The 10SI alternator only needs one wire connected from the main battery terminal to the regulator to begin charging properly if you've got the right regulator installed in it. There are lots of threads that detail the process. The second terminal on the regulator is only necessary if you choose to run the idiot light instead of or in addition to an ammeter.

Install a gas tank sending unit from a 12-volt truck. Problem solved!

The only voltage-sensitive dash gasuge is the gas gauge. The ammeter might need a shunt to prevent it from pegging right after startup if you've got a low battery, but it's not voltage-sensitive. It measures current, not voltage.

If you need a specific voltage supply to something (can't imagine what) use a potentiometer with enough current-carrying capacity to run the accessory, and use the variable-output wiper to dial in whatever voltage you need with the item in operation. Then lock the shaft down to prevent it from drifting off the setting.

There are plenty of 12-volt aftermarket heater blower motors that should fit your application in case you can't get the GMC unit to turn the right direction.
Jerry



"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
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