Temperature gauge

[jvsimmons]

After swapping a 2.25L diesel for a 2.5 petrol engine in my 1983 S3 County 88 the temperature gauge does not work. All other gauges work. The 2.5 petrol engine came from a 1986 Defender. I've checked the wiring to the gauge - all seems good. I pulled both sensors thinking I would just swap them but found that the threads on the sensor from the 2.5 are different from the ones on the sensor from the diesel 2.25. I could purchase a new sensor for the 2.5 ( maybe the sensor is bad), but thought I would ask "the forum" if there could possibly be an electrical incompatibility issue, AND if there is what sensor would I purchase that would be compatible. Really don't want to replace the gauge. Thanks for any suggestions / opinions.
Jim

[siiirhd88]

You can check the gauge circuit by grounding the sensor wire. The gauge should peg hot if the wire is grounded. If not then there is an open in the circuit. The sensor varies the resistance to ground as it heats and cools, and I think the sensors on the 2.25 and the 2.5 use the same resistance.

Bob

[jvsimmons]

Bob, Thank you! I did test to ground as you instructed. Gauge did indeed peg to the hot side. I assume then that this indicates that the sensor is faulty? Is this correct? Thanks again for the help,
Jim

[siiirhd88]

Yes, it is likely the sensor that is failed. The sensor needs to have a good ground to the engine, so any sealant on the threads can prevent it working or give innacurate readings.

I have seen a few posts on UK forums that suggest the 2.5 sensor is a different ohmage than the Series. I'll check around a bit more and see what I can find.

Bob

[siiirhd88]

What is the sensor thread size on your 2.5 ? If is 16 X 1.0 metric thread, Steve Parkers in the UK makes an adaptor to fit the Series sender.

https://www.steveparkers.com/product/spck224tadaps3l-conversion-temp-sender-adaptor-land-rover-s3/

A specific Range Rover sender part # AMR1712 is 16 X 1.0 thread and is supposed to be compatible with the Series gauge.

Bob

[jvsimmons]

Bob, I will purchase a new sender and see what happens. I'm pretty sure that the threads on the currently installed sender do not have any thread sealer or anything else that would interfere with it getting "ground". But I'll find out when I pull it to install the new sender. Was hoping that there would be a reference to a sender that I could buy locally. Any thoughts on that?
Jim

[siiirhd88]

I doubt you will be able to purchase a sender locally, unless there is a British specialty shop. I've seen reference to the Series typically using either a sender with 240 ohms cold / 19 ohms hot or 300 ohms cold / 45 ohms hot. The SIII sender has 5/8-18 UNF threads. I don't know what the threads are on your 2.5. I know they had at least two different senders.

Bob

[jimrr]

just to complicate things: My new S3 temp sender requires a $40 adapter to match the threads. I've not installed it as I don't want the added piping sticking out there inducing stress and potential leaks but can eventually make my own or something.
I believe my issue really is the voltage regulator in the dash that apparently sends intermittent or momentary pulses of electricity to the senders to "steady" the guages which are slow response, this preserves the guages.
i believe the sender for both gas and temp work fine on my S3 but the new voltage stabilizer I got from RN #5-K-07-06 or PLE826 or 44234 proline made in china? probably the ple826#. i'm pretty sure that's my issue and may be of help to you?
I have reasonably well researched my issue here as i even bought a new fuel sender that i now do not need as the original works fine, same no doubt with the temp sender.

[jvsimmons]

I am currently on a trip so my temperature issue will have to wait till I get home in June. I will probably just buy a new sensor and see if that fixes the issue. Since my fuel gauge works fine I suspect it is not the voltage regulator. As it has been pointed out I may have to buy the adapter and the sensor specific for the S3 rather than using the sensor used in the Defender petrol engine even though there is only 3 years separating my S3 and the Defender engine.