Having got my nice new engine turning over, I need to solve a couple of other problems.

When I turn the ignition on and start up the engine, the temperature gauge starts off low, then rapidly climbs to maximum reading.

There's no problem with the engine temperature, I can put my hand on the top of the radiator, and I can feel the radiator temperature lowering as I check out the radiator core lower down.

The temperature sender is part 560794, and the gauge is part 560746. They should match up.

The resistance across the gauge is 60 ohms. The resistance of the sender when cold is 390 ohms, and 60 ohms when hot. The body of the sender is well earthed, and it's brand new.

Can anyone with a multimeter confirm that those readings are correct?

Can anyone come up with some other trouble-shooting approach?

Thanks, Peter

Assuming you are talking about the factory temperature gauge fitted 1967 on, (and the part numbers confirm this) then the problem is most likely that the voltage stabiliser is :-

1. Missing or not in the circuit
2. not properly earthed (on this model it is mounted on the bulkhead and relies on the mounting and the bulkhead for earthing)
3. Faulty.

(in that order)

The voltage stabiliser gives 10v nominal, but this is actually an intermittent 12v switched on and off by a bimetal strip with a period of several seconds.

If the stabiliser is present and working (confirm by switching on the ignition and check voltage at the sender, should go on and off, also is the fuel gauge behaving), you may have a problem with manufacturing tolerance of the gauge and/or sender. I had this, so the normal running temperature was only just below the hot mark. I simply experimented with small resistors until I found one that gave the normal reading when in series with the sender.

John

__________________
JDNSW
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol

Thanks John. There's no voltage stabiliser in the circuit - this is running on a test bed, see the circuit diagram attached. I'm assuming the voltage stabiliser in the alternator will be adequate for the job.

If my arithmetic is correct, the resistor would need to be 2/10*(60+390) ohms, say 10 ohms at 5%?

Peter

Attached Images

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Thanks again John - a 39 ohm resistor did the job.

Peter

Peter

The voltage stabiliser/resister for the guages is usually screwed to the back of the instrument cluster. Its a little rectangular metal box with 3 Lucar (blade) connectors pointing out.

Diana

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Thanks Diana, that sounds like part 148876, from a Series 3. Do you think it's required, or is it an optional extra?

Peter

The voltage stabiliser is not optional. The reading of the gauge depends on the supply voltage and the resistance of the sender. The alternator regulator limits the maximum voltage to about 14v, but the voltage with the engine idling after starting is probably less than 12v, and this variation will make the readings pretty meaningless. The stabiliser from the Series 3 and 2a is the same except that the Series 2a one does not have a connection for earth, but relies on being earthed by its mounting screws.

John

__________________
JDNSW
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol

Thanks John. I'd better set about getting one. Can you tell me what the I and B markings on the pins mean?

Peter

Not absolutely certain - I'd have to look at one to confirm, but I think that B is for Battery, and I is for Indicator or gauge.

John

__________________
JDNSW
1986 110 County 3.9 diesel
1970 2a 109 2.25 petrol

yup