Packard Forum Index » V-8 (1955-56)

I know. That's what is so aggravating trying to troubleshoot older stuff with newer test equipt--have same problems in my day job. Depending on the response time of test equipt, some digital VOMs don't have time to respond with the narrow pulses so read low, others respond but the digital readouts don't completely display. Others so sensitive they pick up all the extra garbage like the spikes on those waveforms and skew the readings. The old Simpson or Weston analogs are best for this stuff. You said "IC" regulator. Is yours the original or is it the newer IC type. Those do have a constant out.

The oscilloscope view shows exactly what is happening. When the heater opens the contacts, nothing and when they close again, 12v. The average of 5v output depends on the frequency of the open/close cycle. The electronic regulator purchased should have resolved the issue unless there is a missing ground connection or reference voltage somewhere--or the gauges are actually toast.

As the electronic IVR I bought was plastic, it had a ground wire on it to attach to the car instead of the original grounding through the metal case. I couldn't tell from the diagram if there was any other grounding needed other than what is in place from gauge to gauge.

Would the gauges running on 12v for a long time not be able to readjust for the 5v?

Thanks
Gene

If you can measure 5v from any point on the metal of car to the output of the voltage regulator at the gauges, then ground is OK. If that is good, then suggest checking the gauges to be sure they haven't burned out. It's not absolutely necessary but I suggest you remove the 2 wires on gauge being checked to eliminate possibility of different current paths, if that is a project then the sender wire only will do (careful not to twist the stud and break wire inside). Each gauge heater should measure around 12-13 ohms across the 2 terminals. If gauge checks OK, then ground one meter lead and check gauge sender wire. Orange for gas, dark green for temp, and dark blue for oil. Depending on which sender and the status, each should measure somewhere around 10 ohms minimum and 75 or so maximum.

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