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P38 V8 Coolant Gauge Sender Ohms/Temp


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Does anyone have the resistance measurements (Ohms / temperature) of the GAUGE sender (not the ECT for the ECU) for early P38's?

I was sure it was in the RAVE manual or something but jiggered if I can find it :huh:

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Forgive a mere mortal wot hasn't had a V8 now for many a long year.........:huh:

Apparently Rave does reference it somewhere:... saw a reference to section 19 somewhere?

In the Rave manual, it shows a picture of two engine coolant temperature sensors, but in the description, it just talks about one (my guess it is talking about the one with the single bullet connector. It says it should measure 28k ohms at -30 degrees C, 300 ohms at 85 degrees C, and 90 ohms at 130 degrees C.

What is the other sensor for (the one with a two prong connector)?

Found the above comment Here

Also found This and This too, on the basis that the sindle pin sensor is AMR1425, 'green' which I think is correct.:unsure: 

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Hmm, I cut and pasted the above from my notes files, I should have read it first - I have a second file in my archive with numbers that much more closely match the aulro link that Blanco posted.

As a penance, tomorrow I will put the kettle on and measure one....again, and this time I'll try not to lose the test data :rolleyes:

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Measured a new Bearmach AMR1425 sensors today. Also did AMR3321 and ERR2081 since they were handy. Posted here so they don't get lost again.

(First column is Temp in C, Second is Resistance in Ohms. Open in a text editor if you don't do spreadsheets.)

AMR1425.csv AMR3321.csv ERR2081.csv

Edited by TSD
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  • 2 weeks later...

Just for completeness, added ETC8496 to the list. This might be a useful one for someone, as it's very close to AMR3321 in performance, but packaged like ERR2081, so fits the sensor boss hole in the middle of the 300tdi head. Might be a useful conversion part for someone?

ETC8496.csv

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  • 1 year later...

I might mention that if you were trying to fabricate a sensor (eg in a stud to suit a foreign engine), R25=2k2 B=3950 thermistors are not too hard to obtain and might be a good enough substitute for AMR3321, ETC8496, ERR2081.

 

Owen

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  • 3 weeks later...

So, putting this information to good use...

The question here is whether in a particular vehicle, the dashboard gauge and ECT sensor are compatible.

1. 'cold' resistance of the ECT with wire removed is 2730 ohms at around 20C. This hints the ECT sensor is unlikely to be a AME1425 but one of the others mentioned (which are fairly similar).

2. Connecting to parallel resistors for total R=155 ohms yields the following:

ECT-155.jpg.ae8ab640f906d870a9c2dc495ac554ea.jpg

3. Connecting to parallel resistors for total R=27.5 ohms yields the following:

 

dECT-27.5.jpg.c2d8b61d905bf58e65b93ef949aa4625.jpg

 

4. Calculating the expected temperature of the AMR1425 at 27.5 ohms from the constants above, we get:

Screenshot-210406075152.png.6bc739f6ace34299bcd09c08c3a835dc.png

... which was bang in the middle of the red zone.

 

This gauge appears to be compatible with the AMR1425 ECT sensor, not the one fitted to the engine.

This seems to be the result of an unprofessional / half baked conversion of a petrol vehicle to a diesel engine.

Owen

 

Edited by owenduffy
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