Oil Temp Sensor & Pressure Switch - When to Replace

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Dennis Vogel
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Oil Temp Sensor & Pressure Switch - When to Replace

#1 Post by Dennis Vogel »

What is the usable lifespan for the oil temperature sensor and oil pressure switch? Is there an easy way to tell if they require replacement when the car is not running?

I am eyeball deep in the rebuild of my engine. My plan is to replace most, if not all, engine related electrical wiring, and rubber. So I'm about to place an order for distributor cap, spark plug wires, etc. Wondering if I need to add the oil temp sensor and pressure switch to the growing cart. :?:
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John Brooks
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Re: Oil Temp Sensor & Pressure Switch - When to Replace

#2 Post by John Brooks »

Dennis you can test both sensors pretty easy if you have a multi meter, a cup hot water for the temp sensor, compressed air for the oil switch. I have a couple that have been working for 50-60 years and match my engine test bench.
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Dennis Vogel
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Re: Oil Temp Sensor & Pressure Switch - When to Replace

#3 Post by Dennis Vogel »

John Brooks wrote: Wed Mar 27, 2019 4:15 pm Dennis you can test both sensors pretty easy if you have a multi meter, a cup hot water for the temp sensor, compressed air for the oil switch. I have a couple that have been working for 50-60 years and match my engine test bench.
Thanks for the suggestion John. Am I measuring ohms? Can you be more specific in what readings I should expect? I am not super savvy with troubleshooting electrical, as you can tell.
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Dave Wildrick
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Re: Oil Temp Sensor & Pressure Switch - When to Replace

#4 Post by Dave Wildrick »

Dennis Vogel wrote: Thu Mar 28, 2019 1:29 pm
John Brooks wrote: Wed Mar 27, 2019 4:15 pm Dennis you can test both sensors pretty easy if you have a multi meter, a cup hot water for the temp sensor, compressed air for the oil switch. I have a couple that have been working for 50-60 years and match my engine test bench.
Thanks for the suggestion John. Am I measuring ohms? Can you be more specific in what readings I should expect? I am not super savvy with troubleshooting electrical, as you can tell.
A few years ago, I tested my 2 original 6V temperature sending units (made in the '60s).
They each gave an ammeter reading of 28 ohms at room temperature (75-78 degrees F) and 35-36 ohms at 162 deg. F (72 deg. C) in hot water.
The 28 ohm reading at room temperature agrees with what electrics guru Joe Leoni told me it should be.
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Re: Oil Temp Sensor & Pressure Switch - When to Replace

#5 Post by Dennis Vogel »

Dave Wildrick wrote: Thu Mar 28, 2019 3:49 pm A few years ago, I tested my 2 original 6V temperature sending units (made in the '60s).
They each gave an ammeter reading of 28 ohms at room temperature (75-78 degrees F) and 35-36 ohms at 162 deg. F (72 deg. C) in hot water.
The 28 ohm reading at room temperature agrees with what electrics guru Joe Leoni told me it should be.
Not sure if I did this right. I have cheap multimeter with limited options. I set it to measure resistance (ohms). I put the red (positive) lead on the sensor end, and the black (negative) lead on the connector end.

For the temp sensor, I got:
  • 45 ohms at 180 F
  • 41 ohms at 170 F
  • 28 ohms at 72 F
Seems in line with Dave's readings.

For the pressure sensor was a bit wonky. I got:
  • 0.x with nothing going
  • OL (think this is overload) when using compressed air
So something is happening with each. I guess I'll consider them good?
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Martin Benade
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Re: Oil Temp Sensor & Pressure Switch - When to Replace

#6 Post by Martin Benade »

Both sound good. The pressure switch is zero ohms, as in fully connected at zero pressure. Once you get above 7 psi or so the contacts open, your meter basically said it was such high resistance that it could not measure it. That's OK.
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