Temperature guage and sender issues.

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Mar 19, 2020 | 08:55 AM

#16

FuzzFace2

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From: Angier, NC

Quote:

Originally Posted by kr98664

I think the "ECT sensor" was only for vehicles with computer-controlled engines. This sensor fed coolant temp data to the computer only, not the gauges.

A separate coolant temp sensor fed info to the gauges. All three gauges (coolant temp, oil pressure, fuel quantity) are the same internally, with different labels on the face. The sensors all operate 10 ohms = high, 73 ohms = low. Details here, see the second page:

Fuel Tank Selector & Gauges - Gary's Garagemahal (the Bullnose bible)

That is why I said to swap wires going to the oil & temp senders to see if the gauge is bad or not with jumper wires.
Dave ----

Mar 19, 2020 | 08:56 AM

#17

Kramercd

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From: Caraway, AR

Good idea, that's how I checked my thermostat before I installed it. Will try that soon. I'm surprised you haven't recommend a fancy DVOM with temp probe yet, you know, for when the money's not funny.

Mar 21, 2020 | 09:36 PM

#18

kr98664

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Quote:

Originally Posted by Kramercd

What I'm curious about is the resistance values, are they linear? If I can map a couple of points can I calculate any given temperature given the resistance?

I spent some time playing with the gauges today. The resistance curve definitely is NOT linear.

Per the EVTM, the sensors all operate 10 ohms = high, 73 ohms = low. Mid travel was 28 ohms. I was was expecting more like 41 ohms to put the needle in the middle, but that wasn't the case. All three gauges checked the same at high, middle, and low. The high and low values agreed with the EVTM, so I'm pretty confident 28 ohms for mid travel is also correct.

Mar 21, 2020 | 10:23 PM

#19

Kramercd

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From: Caraway, AR

I was talking about the temp sensor, if I could measure it at 2 temperatures and then use those numbers to calculate that the temperature is for a given meter reading. I haven't gotten there yet. I scored some free gauges I'm going to hook up to test things with. But I've got a connector(of sorts) for my temp sensor. I've got test probes off an old dead DOVM, and I have a really nice build your own connector kit. Plan is to put the waterproof auto electrical connectors on the meter leads, and the wires going to the sensor. Then I'm going to make another connector going to alligator clips and any other leads I deem useful and add all of that to my test kit. After I get that done I'll boil the sensor slowly and make some notes and see if I can predict temps with it.

Mar 22, 2020 | 08:52 AM

#20

Franklin2

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From: Virginia

Do you guys realize what you are debating? Is the sensor linear? What if it's not linear? That just means it rides a little different in the word "normal" on the gauge? Does it really matter? I think not. If the gauge had numbers, then I think it would matter.

Sorry for the interruption, continue on.

Mar 22, 2020 | 09:16 AM

#21

packagerjr

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Quote:

Originally Posted by kr98664

My experience lines up with this. The warmer end of the gauge range responds with much larger amplitudes per an absolute temperature change relative to the colder end. I suppose it stands to reason if only 18 ohms exist between midpoint and high that it’ll be more sensitive than the 45 that exist between cold and midpoint.

Mar 25, 2020 | 03:10 PM

#22

BlueWhiteFord

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From: Wolfsburg

I have had something like that happen too. After putting in a new temp sender the before nonfunctional temp gauge started working. Always read fine. Sitting slightly right of center. I could actually see the thermostat opening as the needle dropped a little when it did so. Everything was fine until I was on a 2 hour drive. about 1:15 min in, the temp starts rising and sits right at the line for hot. I was freaked out the entire rest of the way, not fun. When driving home the same thing happened. Since then I have used the truck to pull things around the house and it has never risen above the slightly right of center position. Not even when I took it out and gave it a good bit of gas. Seems like these aftermarket senders can be all over the place.

Mar 25, 2020 | 04:16 PM

#23

Kramercd

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From: Caraway, AR

I want to know what the different color insulators indicate. I have a feeling they correspond with thermostat temps, to keep the needle about middle of the "gauge" when it's at operating temp. Got that test on the pile of to dos whenever.