Engine Oil Temp Sensor biased by running AC? (random discovery 2025 RR)

[TSY]

Ok - had a long drive today from St George UT over to Santa Monica. Had some long runs where temps were steady at 91 degrees and speed on cruise control was set at 80.

I have both transmission and engine oil temps selected in my view gauges pack.
... over the course of the day I noticed (and because I had nothing better to do, lol... ) I got to test this repeatedly.

Engine oil temp displayed drops about -15-18 degrees if AC is running - and returns +15-18 when it's off. ( yes, I tried it it both on, off and repeated it... takes about 20 minutes for full influence to show in the engine oil temp gauge.)

Anyone else notice this? I haven't had a chance to investigate if any of the AC coolant lines are near the oil temp sensor... anyone know?

I figure it's just a case of one AC component affecting heat soak of the sensor....

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[bigb]

Seems strange. No chance the oil temps could have been related to gradual grades and just a coincidence? I like to monitor elevation which tells me if I am climbing, descending or level. Sometimes you can't tell. Did you happen to notice if there were any gear/RPM changes?

External/ambient temps should not affect a sending unit in the engine block.

 

[scout]

Happens to mine too. It’s a dramatic change.

 

[embedded rock]

Is the radiator cooling fan soeed programmed progressively with engine temps? If so, it's possible the fan speed program is stepped up when the AC is operating.

 

[bigb]

Is the radiator cooling fan soeed programmed progressively with engine temps? If so, it's possible the fan speed program is stepped up when the AC is operating.

I thought about that too but at 80 MPH how much is a fan going to matter? Unless it's the shutters you are thinking about? I never had a vehicle with shutters before so that part is still kind of mysterious to me.

 

[bigb]

So I Googled "do intercooler shutters open when AC is switched on" and may have found the answer

https://www.google.com/search?q=do+intercooler+shutters+open+when+AC+is+switched+on&sca_esv=5b71cfa89013eb9f&sxsrf=AE3TifMbDJ3zOscuNaWtJGNumbLJB_V-_g:1757943864188&ei=OBjIaPyYC_OlkPIPiabDkA8&ved=0ahUKEwj8lL2c89qPAxXzEkQIHQnTEPIQ4dUDCBI&uact=5&oq=do+intercooler+shutters+open+when+AC+is+switched+on&gs_lp=Egxnd3Mtd2l6LXNlcnAiM2RvIGludGVyY29vbGVyIHNodXR0ZXJzIG9wZW4gd2hlbiBBQyBpcyBzd2l0Y2hlZCBvbjIFECEYoAEyBRAhGKABMgUQIRigATIFECEYqwJIhmtQAFjhZnAAeAGQAQCYAYEBoAGHKaoBBTE1LjM2uAEDyAEA-AEBmAIzoAKWLMICBBAjGCfCAgoQIxiABBgnGIoFwgILEAAYgAQYkQIYigXCAgoQABiABBhDGIoFwgIOEC4YgAQYsQMYgwEYigXCAhEQLhiABBixAxiDARjUAhiKBcICDhAAGIAEGLEDGIMBGIoFwgIOEC4YgAQYsQMY0QMYxwHCAgUQABiABMICCBAAGIAEGLEDwgIIEC4YgAQYsQPCAgoQABiABBgUGIcCwgIGEAAYFhgewgIFECEYnwXCAgcQIRigARgKmAMAkgcEOS40MqAH97oCsgcEOS40MrgHlizCBwkwLjcuMjYuMTjIB8YC&sclient=gws-wiz-serp

So they could be opening anytime the AC is switched on, or because of the increased load/heat from the AC operating.

 

[TSY]

Seems strange. No chance the oil temps could have been related to gradual grades and just a coincidence? I like to monitor elevation which tells me if I am climbing, descending or level. Sometimes you can't tell. Did you happen to notice if there were any gear/RPM changes?

External/ambient temps should not affect a sending unit in the engine block.

I made a point to watch for all above - fyi : I've noticed it before (ex. hwy 40 driving from Mojave over to Flagstaff and then up to Durango ) - again really consistent roads and was repeatable.

To bigb's point above : looks like it's a compromise between "aero" closed mode and "ac" open mode.

https://thebronconation.com/general...-disconnecting-active-grill-shutters-t.11870/

I guess it's time for the volt meter and terminators - at least for summer temps...

 

[embedded rock]

I thought about that too but at 80 MPH how much is a fan going to matter? Unless it's the shutters you are thinking about? I never had a vehicle with shutters before so that part is still kind of mysterious to me.

Hadn't considered shutters or how they interact with fan speed.

Is there a gap between the condenser and the radiator? Maybe airflow from speed is cutting the remaining airflow to the radiator? I've not seen the configuration. If there is a gap, or the condenser simply reduces airflow, the cooling fan is needed even at speed.

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