Oil sender worth the name - is there one?

[Voss]

I have spent some effort in calibrating my instrument cluster gauges (the small ones) to my real senders. Despite the old design of these gauges, they can be calibrated to be quite accurate.

The only problem I have is the oil sender. I have tried 4 different units. 3 of them were more or less crap out of the box. They indicate a pressure yes, but they are not linear, and have different characteristics at pressure increase vs decrease. The fourth which I got from Richard Ehrenberg is the least bad one. It is far from good however. None of these are useful if you are interested in having any kind of correct readings. More or less only useful as an idiot light.

When I characterized these, I took ohm readings for each sender on bench using shop air and a pressure regulator. The issue are in the design of these senders, for sure. I know fluctuating gauges or incorrect readings can be caused by voltage regulators gone bad, circuit board pins and other bad connections. But that is not the case here. For the moment I have a mech gauge in the Charger. I have kind of given up the hope to find a decent oil sender compatible with these gauges. A bit frustrating that the sender is the weak part. If the sender would behave well it would be easy to calibrate the gauge to show correct and accurate readings.

Does anyone know about a source for a sender actually worth the name?

[Pete in NH]

Hi,

Chrysler gauge systems are not linear. 10 Ohms = full scale, 24 Ohms= mid scale and 73 Ohms = the bottom of the scale. If it was a linear system mid scale would be around 42 Ohms, not 24. All Chrysler shop manuals of the period describe this system and it applies to all the gauges, fuel, oil and temperature.

[Voss]

Hi,

Chrysler gauge systems are not linear. 10 Ohms = full scale, 24 Ohms= mid scale and 73 Ohms = the bottom of the scale. If it was a linear system mid scale would be around 42 Ohms, not 24. All Chrysler shop manuals of the period describe this system and it applies to all the gauges, fuel, oil and temperature.

Thx Pete, fully agree with what you are saying. I described my findings in an incorrect way. The problems I've seen are mainly 3.

1) If you increase pressure, resistance for some senders actually INCREASE within a certain range, then drops as expected when pressure is further increase.
2) When pressure drops, the sender does not reflect that properly. You need more or less 0 psi to "reset" the part. From what I read and also what R Ehrenberg said, this is due to the design. Obviously not a good thing.
3) The sender from R Ehrenberg, made under a US patent, has a type of behaviour in which the resistance is constant over a certain pressure range. Ie between 30-40 psi the same resistance is measured. A small increase to say 41 psi makes the resistance jump to a lower value. Not good, but the good thing with the patent is that the hysteresis behaviour explained above is solved, at least to some extent.

Still, I see the sender's characteristics as the weak part. Maybe I have had bad luck but considering I've measured 4 of them I'm sceptic about throwing more money on this...