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Oil pressure and temp sensors


LotusFella

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I haven't finished, but added a dual oil pressure / oil light switch.  It was VDO stuff and I wired it to the existing dash light for low oil pressure.  To be honest life got in the way of me putting the wires for the oil pressure gauge in the cabin and the other issue is where to put a small VDO electric oil pressure gauge that looks OK?  Whats the best place to run the wires into the inrterior?  The cubby hole below the radio is really not big enough for the guage???  I did confirm that the dual oil pressure sender does work as I hooked up the guage without installing it.

 

Thanks Mark

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  • 2 weeks later...

Hello Chris

'96/'97 V8s have a directly driven oil pressure gauge from a block transducer, there is no ECM connection or data available from this. This was deleted on '98 on models.

There is an oil temperature sensor on '98 on models (although my '96 appears to have been fitted with one) but as that post explains, there isn't any documentation or wiring diagram that includes what it is connected to. I doubt very much that it ECM connected and that it is a switch that illuminates the coolant warning light directly if the oil temperature goes higher than a preset.

There is no OBD data for any oil parameters as the ECM doesn't need to know about them and is not wired up anyway. Sorry!

I tempted fate...now my Esprit V8 IS in bits...(sob)

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  • 2 years later...

Have been looking into the MY 98+ oil temp sensor, which is located in the oil sump drain plug. Realize this is an aged post but I was wondering if any additional info has turned up in the meantime, and I have a question. 

Specifically, given the lack of technical documentation, I am theorizing the oil temp sensor is in fact connected to the ECU and not directly to the dash tell tale lamp. Following is the thought process.

That tell tale lamp serves 3 functions, it indicates:

1) low coolant level

2) high coolant temp

3) high oil temp

If condition (1) occurs the lamp is lit solid ie no flashing. I believe the lamp is connected directly to the coolant level switch in the coolant reservoir, which could enable the steady lit indication by simply providing the path to ground (the lamp itself is supplied with 12v).

If conditions (2) or (3) occur the lamp flashes. It seems very unlikely this could be enabled directly by a physical sensor/switch. But it could be enabled by the ECU logic where the ECU provides the ground path. The wring digrams show the coolant temp sensor is connected to the ECU. So it's most likely the oil temp sensor is connected to the ECU as well, and not directly to the tell tale lamp. 

The oil temp sensor could be a simple on/off switch or a variable resistance (thermistor) device.

My question is does anyone know which it is? And if it's a thermistor what is the range of resistance values?

Edited by 71Type65
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Looking at ECU pinout, I can see that pin 10 was reserved for Oil temperature.  You could buzz that back to the oil temp connector to check if that is the case on your loom.

I've just checked the oil temp sensor here and it's definitely a thermistor. Even with a crude test:

- 5.1KΩ at ambient, dropping to less than 1kΩ at 95deg.

 

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1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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@LotusFella Check out my solution : I bought from a pre-1998 Lotus Esprit V8 the Turbo and oil Pressure gauges together with the sender units, and for a 1995-1998 Lotus Esprit S4 the oil temperature gauge and sender unit... The first two the facia at night was red colored, white the third had green light... I could not change the first two colors, so i made the third one red too... I installed an extra pipe to install factory OEM low oil pressure sender, NEW oil pressure gauge sender and NEW oil temp gauge sender..

I didn't want to mess with the clean look of the 2001 V8 dash, so I installed them below the climate control switches.. Check out below

 

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5 hours ago, mike_sekinger said:

Looking at ECU pinout, I can see that pin 10 was reserved for Oil temperature.  You could buzz that back to the oil temp connector to check if that is the case on your loom.

I've just checked the oil temp sensor here and it's definitely a thermistor. Even with a crude test:

- 5.1KΩ at ambient, dropping to less than 1kΩ at 95deg.

 

Awesome, thank you! Interestingly, and assuming the 95deg is F, those resistance values seem to track fairly close with the coolant temp sensor, as per the chart in the Code 15 fault diagnosis section of the service manual.

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It is certainly not the same part as the ECT sensor located in the block.

Is would be easy enough to map the temp and resistance values if that is required.

1996 Esprit V8, 1998 Esprit V8 GT, 1999 Esprit S350 #002 (Esprit GT1 replica project), 1996 Esprit V8 GT1 (chassis 114-001), 1992 Lotus Omega (927E), 1999 Esprit V8SE, 1999 Esprit S350 #032, 1995 Esprit S4s, 1999 Esprit V8 GT (ex-5th Gear project), 1999 Esprit V8SE ('02 rear)

1999 S350 #002 Esprit GT1 replica

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13 hours ago, mike_sekinger said:

It is certainly not the same part as the ECT sensor located in the block.

Is would be easy enough to map the temp and resistance values if that is required.

No, not required at this point but thanks! Didn't mean to confuse the issue by mentioning the ECT sensor, just pointing out they seem to have similar resistance values. Definitely two different sensors.

Although I have seen where some owners replaced the Esprit oil temp sensor with a commonly available and much cheaper coolant temp sensor, which looks physically identical. The question had come up whether the low cost alternatives are electrically compatible.

https://www.ebay.com/p/1550780967

https://www.amazon.com/Standard-Motor-Products-TX18T-Temperature/dp/B004C0RQSI

So I think that's still a bit of an open question. Which might be useful to answer from the standpoint of parts cross-referencing. 

Edited by 71Type65
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The FAE 33370 reputedly cross references to the Bosch 0 280 130 026

Temperature [°C] Resistance Ω [Ohm]
-40 45,313
-30 26,114
-20 15,462
-10 9,397
0 5,896
10 3,792
20                2,500 (+/- 5%)
30 1,707
40 1,175
50 834
60 596
70 436
80 323
90 243
100 187
110 144
120 113
130 89
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