74 duster my temp and fuel gauge were going to full so I purchased a new ivr, now the gauges don't move at all, so I put the old ivr in and the gauges go to full, so is the new ivr no good?
Thanks
Thanks
Ivr
- Thread starter dart67
- Start date
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Sound like it is.
All gauges go to full, there may be a short circuit somewhere instead of the limiter being the fault. Modern regulators have built in protection that turns them off when there is a fault downstream. Diagnosis is key. Something simple, Disconnect the temp sender and see what fuel gauge alone does. Then disconnect fuel sender and try temp gauge alone.
Since the later model wiring harnesses are plagued with issues, the fault could be most anywhere. 1 possibility is the white plastic engine harness connector. They routed the alternator wires through here with several others. Those connectors melt and create all sorts of crossed circuits. Good luck
Since the later model wiring harnesses are plagued with issues, the fault could be most anywhere. 1 possibility is the white plastic engine harness connector. They routed the alternator wires through here with several others. Those connectors melt and create all sorts of crossed circuits. Good luck
rich006
Learning as I go
If both gauges read high, I would suspect both are shorted. Each one should have its own path to ground through its sending unit, but it sounds like both sending units are being bypassed.
67Dart273
Well-Known Member
No, most likely the IVR. this is "classic" IVR failure, whether Mopar, Ferd, or whoever else used them
BillGrissom
Well-Known Member
For others, the dash IVR simply outputs +5 VDC. Check that it is doing its job w/ a multimeter. The after-market adjustable types let you tweak the output so your fuel or temp gage reads full-scale correctly (not both).
nm9stheham
Well-Known Member
Actually no, the IVR does not put out 5v. It puts out a pulsed 12V that is 12v for about 17-18% of the time and 0 volts for the rest of the time. It causes the thermal power in a resistive gauge circuits to be the same that a steady 5v source would cause..... and since these are thermal gauges, that is what counts. A circuit like Tim references will generate a steady 5 volts. The RTE limiter actually simulates the old style IVR, with a pulsed 12v output.
All true. You cannot measure voltage output from old style IVR, It is off most of the time, And IMO not very reliable. that is why I built the new regulator. Seems to work well.
rich006
Learning as I go
I measured my (original) limiter with a device that records voltage to a laptop and I'm getting 6.2 volts about 25% of the time, otherwise zero. That gives me an equivalent voltage of 3V (square root of 0.25 x 6.2 squared). Not surprisingly, my gauges read low. I was thinking I might fix it just by bending the bimetallic strip to make it stay on more of the time, but if it's supposed to be passing 12V there must be some excess resistance somewhere.
nm9stheham
Well-Known Member
Mmmmmm..... I would not necessarily trust a computer recording device unless I had tested it on some rapid waveforms before and knew its accuracy. I have used an oscilloscope like Skykeith to see the pulses. If your IVR is really putting out a low voltage of around 6 volts, then the contacts may be be burned inside. Not sure if a contact file would clean it up or not. If it did, I bet some silver plating powder would fix it up..... or just get another one!
67Dart273
Well-Known Member
Stop screwing around ...........! ! ! ! !!!!!!!!!!!!!!!!!!!!!
Or you are liable to end up with some "smoked" gauges!!!!!!!!!!!
Either buy or build a solid state replacement IVR
rich006
Learning as I go
Oh dang. I used a voltage sensor that is designed for school physics labs. I set it to 200 samples/second, so I thought it was good. But now that you mention it, I looked up the specs and it only measures up to 6 volts! So of course my reading tops out at 6. D'oh! Clearly I have some more troubleshooting to do.
Much appreciated, I'll let you know if I need one.
nm9stheham
Well-Known Member
Yeah... that computer hook up stuff is rarely lab grade equipment.... the software guys who know how to make it work with a USB computer interface rarely know much about actual hardware and the laws of physics. You ought to see the chaos that results when a mobile wireless link is added in....."What, the message didn't get through and I have to resend it? What do you mean about 'message acknowledgement?" LOL
rich006
Learning as I go
I redid my measurement today using the same sensor but with a couple of resistors as a voltage divider to avoid saturating the sensor (I put the two resistors in series between the temp sensor connector and the temp sensor, and measured the voltage across one of them, then did some math to adjust my measurements). The voltage limiter's outpout cycles between 10.4V and 0, with an rms of 5.3V (that's without the engine running). So it looks like my voltage limiter is working correctly, and my low gauge readings must be from some stray resistance down the line somewhere.
nm9stheham
Well-Known Member
There you go... good work to make the device work. And someone else understands RMS....
The gauge issues can be in the sensors or in the gauges themselves. With 10 ohms to ground on each of the gauge lines, the temp sensor should read H and the fuel gauge should read full.
The gauge issues can be in the sensors or in the gauges themselves. With 10 ohms to ground on each of the gauge lines, the temp sensor should read H and the fuel gauge should read full.
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