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> Troubleshooting oil temperature circuit
reynoldslh
post May 9 2025, 11:44 AM
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I am trying to troubleshoot what I think is a lazy temperature gauge response on my car (European 1973 914-4 with combo instrument) which has been in storage for far too long.
The temperature needle does not go above about 1/4 way across even with the engine warm. Either that´s normal, or the gauge is out of calibration, or there is a problem with the sensor, or possible combination of all of the above.
What is the expected resistance range of a working temp sensor in the sump? I suspect its the long snout type 200C sensor which is fitted since the taco plate has the angled sensor mount.
Also how to test the temperature gauge itself?
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Superhawk996
post May 9 2025, 01:13 PM
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Superhawk996
post May 9 2025, 01:14 PM
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Pretty normal for an early gauge with the proper 200C sender Attached Image

Combo (see Fig 3) Attached Image

Test via boiling water or in oil with secondary thermometer.
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Lockwodo
post May 9 2025, 01:48 PM
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The oil temp gauge on my ’74 2.0 barely moves when the car is warmed up, never gets even 1/8 of the way across the dial.
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914Sixer
post May 9 2025, 01:48 PM
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CHECK wire from sender to plug under battery shelf. Probably has high joint (broken wires) under sheath.
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emerygt350
post May 9 2025, 02:37 PM
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Same here. Only time the gauge moves up past 1/4 is when it's hot out and I have been driving hard. Like climbing long long high hills on the interstate hard.
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930cabman
post May 9 2025, 04:31 PM
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Confirm with an infrared point/shoot
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bkrantz
post May 9 2025, 07:16 PM
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Yup. Stock "normal" looks low, and takes forever to get there.
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reynoldslh
post May 10 2025, 06:24 PM
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QUOTE(Superhawk996 @ May 9 2025, 08:14 PM) *

Pretty normal for an early gauge with the proper 200C sender

Test via boiling water or in oil with secondary thermometer.


Thanks Superhawk996, I had seen these useful graphics on another post which made me wonder about my situation. You´ve helped confirm it. Cheers
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reynoldslh
post May 10 2025, 06:30 PM
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QUOTE(914Sixer @ May 9 2025, 08:48 PM) *

CHECK wire from sender to plug under battery shelf. Probably has high joint (broken wires) under sheath.


Bingo, that was one of the first problems I found! And, of course, after fixing it, that´s when I first noticed the gauge response....thanks
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reynoldslh
post May 10 2025, 06:35 PM
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Thanks to all for confirming that my temperature gauge is probably working just fine!
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