My fuel gauge moves a centimeter up from empty with a full tank, oil pressure shows 3/4 movement from zero with engine off, temperature gauge is in red with engine running for 2 minutes, ammeter - who knows if those even work new...

Think my instrument voltage regulator is dead? I just don't really see why I have such erratic readings otherwise!

 

If all the gauges are acting "weird" simultaneously it's a pretty good indication the ICVR is at fault.

To test with a VM, it should pulse 5v every second or so, you can also try adjusting it before replacing, they're 50-60 bucks!

 

As MH said, erratic simultaneous behavior is indicative of a bad ICVR. If the ICVR is bad, all gauges usually swing one direction in unison. The fact that the temperature gauge and oil pressure gauge swing too far sounds like the ICVR output is too high, but it doesn't explain the fuel gauge. Your description points to a bad rheostat or poor sending unit ground - the ICVR could still be outputting too much voltage, but the resistance to ground in the sending unit's path is so high that the needle still doesn't move much. You probably have a combination of more than one problem. Check the output of the ICVR.

The ammeter is not part of the ICVR circuit. However, it's for "show" and wouldn't have worked when new anyway. It's a shunt-style ammeter and has very coarse resolution.

 

Thanks for the reply's. I found a 'new' regulator and ordered that up; figured I may as well with the symptoms. The fuel gauge is strange...I tried the the test with unplugging the wire from the sending unit to ground...and still no change. So...I am hoping I have some better results with the regulator.

The regulator seems like an unreliable part; could you not just use a properly selected Zener diode in reverse with a 5 volt drop? I would think it be more stable and the cost is next to nothing.

 

It could work in theory, but Zener diodes alone are rarely used for such applications because of their practical limitations. Zener-based regulators require you to shunt current to ground at all times and have relatively poor load regulation.

There are folks who use an LM7805 regulator for this application with good results. If you're wanting to do away with the archaic electromechanical regulator and go with an electronic setup, I'd recommend using an LM7805.

 

I only understood 50% of that (or less), FMC you are an asset to this community, I tried to rep but the FTE gods won't allow me.

 

Thanks for the kind words MH!

 

They were late in coming...here's some Johnny Cash sent down Austin way...

 

Check your ground wire on your gas tank sending unit plus check your ground from engine to firewall .Usually there was a ground cable from intake manifold to fire wall . a bad ground will make temp gauge not work and if your fuel sender is not grounded good your fuel gauge won;t work right "IVR unit could be bad but I;d check my grounds first

 

I will take a look at that cable; last I noticed it has some insulation falling off! I recall the 7805 from my electronics days at a company I was with. We used it in a battery discharge indicator; I thought the stuff was almost antique at the time. The idea of the Zener sounded simpler but I am not realy wanting to go through an redesign the whole dash...I just hope I have some positive outcome with a new (archaic - haha) regulator. I will check some other grounds and some wiring but I feel that this regulator may be the culprit. The grounds I had checked; and removing the wire from gauge to (before) sender and connected to ground still yielded the same results.

I'm having so much fun...just need more money...