Two temp. sensors and temp. gauge upgrade

XJ-S
1

During my restoration I have added another temp sensor in B bank where EFI sensor used to be. And mooved the EFI sensor to A bank where air pump vacuum thermo-switch used to be.
Since I now had 2 temp sensors, the idea of using them both for temperature gauge never left my mind… I just had to figure out the way how to do it…
Another idea I had on my mind was to somehow modify this stubid temperature gauge so that its readings would make more sense to “untrained” jaguar user :slight_smile:
After analysing temperure sensor resistance and how the gauge reacts to resistange change a very simple idea came into my mind that could address both of these issues… An idea too simple to be true so I had to do some bench testing…
I have wired up both temp sensors in parallel and here’s what happened:
Engine temp ~85c (185f)

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Engine temp ~90c (195f) 82c thermostats should be fully open by now
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Engine temp ~96c (205f) 88c thermostats should be fully open by now
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Engine temp ~110c (230f)
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Engine temp ~120c (248f)
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With this arrangement I am getting an average reading of both sensors and I think temperature gauge readings will make much more sence now :slight_smile:

1 Like
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So finally I wired up both temperure sensors and whent out for a test drive to see what my temperature gauge will show. One thing for sure my temperure gauge now is much more sensitive to temperature changes. When engine is fully warm, at cruising speeds needle used to be a bit below N. Now it is showing just a bit above N

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When I’m stuck in trafic with outside temperature ~30c (86F) needle used to reach bottom part of the N and would stay there. Now my needle will rise almost to the middle between N and H and would stay there. When I drive out to open road it will go back to previous position just a bit above N.
In real life temperure gauge readings came out a bit higher and more sensitive to temperature changes. I would expect that temperature gauge will reach H ~110-115c (230-240F) which is still below the boiling point and should draw attention of the driver.