Thanx, glad to share it. Bear in mind that my gauges now read low, even with a steady 5v supply. I suspect a previous fidgeteer much like me tightened the tension on the old IVR to get the readings up. I've asked about gauge adjustment on the electrical systems forum with less than encouraging results. The mustangs and fast fords website has an article on gauges with pictures indicating adjustment points on what appears to be the fuel gauge of a late '60s 'stang, but no procedures. It does say one adjustment is for base of needle travel, the other is for sweep. Based on nothing more than this, a day of thought and a couple of diet sodas, my best guess on gauge adjustment goes like this:
1) Given: Current passes through the gauge to the sensor/sending unit, where the amount of resistance determines amount of current flow and therefore gauge needle position.
2) Given: The gauge needle itself resists movement upward, and returns to base on its own as current flow diminishes (I'll refer to this as tension).
3) Assumption, not easily verifiable: Sending unit resistance and needle tension are both consistently progressive through range.
4) Assumption, verifiable if true: The gauges have adjustments for needle base and sweep.
Therefore: I can set needle base at some seemingly appropriate point, ground the sending unit wire to move the needle to the top of its sweep as currently adjusted, and adjust that point to an appropriate location. If assumption 3 is valid, I'll have a useful gauge which I can effectively "calibrate" through long-term observation and familiarity ("That looks normal...."). And if I'm wrong, I can call Autometer
If you're gonna build a solid-state IVR, I think you should be prepared to do something similar. Will follow up.

 

What i did for the temp gauge:
Put new temp sender into pan of veggie oil while reading the resistance. don't remember exact numbers, but around 10 ohms @ 210 degrees f and 15 @260.
Used corresonding resistors to check the gauge 10 ohms read at the N and 15 @ L. No actual numbers on gauge and truck runs at 230 up to 250 with A/C in traffic. Pressure gauge was similar test.

 

Are you absolutely sure that the gauges have a good ground? Do you measure any voltage between the gauge ground on the panel and a chassis (or body) ground?

 

I checked the gauge circuits with an ohmmeter, and all are well-grounded. I also grounded the oil and temp sending unit wires: pressure came just shy of topping the normal range, and temp pegged to the right. Along with everything else already done, this convinced me that both sending units were bad or at least had corroded threads. I installed new units today; pressure now centers over the "m" fully warmed at 2400rpm, and temp settles over the "N" (with a 195 thermostat).
I believe now that the old IVR was adjusted for increased voltage to try to put some life into gauges that were barely reading thanx to poor sensors. The old IVR was still faulty, as gauges would sometimes spike to, but not maintain, seemingly normal readings. The new IVR was probably fine, but readings of next-to-nothing on the gauges led me to believe it wasn't (after all, they did show something with the old IVR). My new solid-state is putting out a steady, verified 5 volts, which eventually led me to suspect the sending units.
I still think building a solid-state IVR is worth the effort. It's difinitely cheaper than buying a standard unit. Time will tell if it will last.
This should be my last post on the subject.

 

thanks for the end of the story,was wondering how it came out,Gary

 

FYI, gauges are still working great. Believe building a solid-state IVR is well worth the effort.