You can test them with an ohmmeter between the terminal and the sender body. The water temp sender can be checked in a hot water bath using SWMBO's candy thermometer (or equivalent) and the oil pressure sender using an air compressor (or equivalent). The sender resistance should be close to something along these lines.....

0 psi or cold engine around 73 ohms.
10 psi or 120*F around 50 ohms.
35 psi or 200*F around 25 ohms.
70 psi or 230*F around 15 ohms.
90 psi or 250*F around 5 ohms.

...or thereabouts. Something way off would be reason enough to replace.....if they're generally close keep them....especially the temp sender as replacements tend to be "off".

 

I have a mechanical oil pressure and water temp gauge on my engine test platform.

You can test them with an ohmmeter between the terminal and the sender body. The water temp sender can be checked in a hot water bath using SWMBO's candy thermometer (or equivalent) and the oil pressure sender using an air compressor (or equivalent). The sender resistance should be close to something along these lines.....

0 psi or cold engine around 73 ohms.
10 psi or 120*F around 50 ohms.
35 psi or 200*F around 25 ohms.
70 psi or 230*F around 15 ohms.
90 psi or 250*F around 5 ohms.

Resistances? on mechanical gauges?

Paul

 

I thought the same thing but the op said he wanted to check his sending units so....

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Only the coolant has a temp probe so I guess I mucked it up.

Around 50 psi on the output side of my air hose got the oil pressure gauge up to 22 or 25 so I'm calling it good. Air compresses after all and oil doesn't.

I did my can trick with the hand torch and the temp ran up to around 195 so I'm calling that one good too.

It is 96 feels like 112 degrees here today. It is way too hot for human beings. I started to get dizzy so I had to quit. Just laying the temp unit on the metal frame of the engine tester registered 135 which moved the needle off the bottom peg. Holy heat wave Bat people.

I was hoping to have the engine fired up by now but I didn't think I was going to have to re-engineer the test stand including re-wire it, replace the starter solenoid and figure out some way to raise the block mounts so my headers will clear. I still need to test the fuel pump but it clacks so thats a good sign at least it hasn't been totally plugged up by fracken dirt dobbers.

 

Around 50 psi on the output side of my air hose got the oil pressure gauge up to 22 or 25 so I'm calling it good. Air compresses after all and oil doesn't.

Not good.

50 psi air pressure should make your oil pressure gauge read ... 50 psi. Has nothing to do with 'compressibility'.

I wont comment on the 'accuracy' of your can/torch 'trick' test.

What's the point in having gauges if they are inaccurate or of unknown accuracy?

Good luck
Paul

 

Boy, was I off in space somewhere... LOL.

 

Psi is psi.....

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