bluef250, you make an excellent point about the mechanical regulator being able to compensate for temperature. That's the main reason I don't like any of the solid-state replacements. Plus the SS ones are big and pump out a lot of heat!
The gauges used in our vehicles are thermoelectric, they use pulsating current to heat a wire that is closely bound to a bimetallic spring that the gauge pointer is attached to. The bimetallic spring has different metal types on each side, as it heats up from the hot wire around it, the spring deflects due to the different coefficients of expansion of the different metals. As with all thermoelectric devices, they can be affected by changes in ambient temperature. When the ambient gets colder, for the same current duration that the IVR applies the gauge needle would deflect less and vice versa it would deflect more when it gets hotter. You donÃ¢â‚¬â„¢t see these differences because the stock IVR is temperature compensated. The IVR works very similar, it uses a hot wire in series with a bimetallic spring that makes and breaks the current thru a set of points. Normally the spring is closed completing the circuit until the hot wire eventually causes the spring to deflect enough and open the points. Once open it cools and eventually closes, repeating the cycle over and over. Now when the ambient temperature gets colder it takes the IVR longer to heat up to the same temperature to break the connection. This is good because the gauge is colder and needs a longer current duration to deflect to the same reading. When the ambient is hot, the IVR takes shorter to heat up. Again, this is good because the gauge doesnÃ¢â‚¬â„¢t need as much current duration to reach the same deflection.
Sorry this got kind of wordy. Another way of saying it is when itÃ¢â‚¬â„¢s cold the IVR works harder to heat up which compensates for the gauges needing more current duration. When itÃ¢â‚¬â„¢s hot the IVR has an easier time heating up which also compensates for the gauges not needing as much current. The point of all this is the SS 5 volt regulator always pumps out 5 volts no matter what the ambient or load conditions are, thatÃ¢â‚¬â„¢s what theyÃ¢â‚¬â„¢re designed to do. Admittedly, I donÃ¢â‚¬â„¢t know how much off the gauges would be with a constant source and wide ambient temperature swings but Ford and other tech manuals all make a point and mention this temperature compensation.
Oh, all vehicles with a radio have a noise-suppression choke installed on the IVR, it's just some solid enameled wire wound around a form.
"Are you gonna make it all 220?"
"Yeah 220, 221, whatever it takes."