|Note: This repair saves over £310+VAT in repair
(new Instrument cluster and fitting charges)
|Fault - Temperature
Gauge (and Fuel Gauge) read mid temperature regardless of engine temp (may
One of the members reported a problem with the coolant
temperature gauge which moved to it's mid position as soon as the ignition was
switched on, even when the engine was completely cold.
Removing the sensor connector made no difference to the display as it stayed in
the mid position. He tried a new sensor on the wire without actually fitting it
into the engine and still the temperature display remained in the centre
position. As soon as the ignition was switched off the needle dropped to the
Other members reported similar faults which in at least one occasion had led to
major engine failure due to overheating. The problem was that the gauge was not
reporting either cold or hot conditions.
Tim then offered the following useful information.
"There are two temperature sensors mounted on the thermostat housing, one for
temperature gauge and one used for PCM reporting.
The PCM sender is of a sensible value ranging from 200k cold to 2k ohms (normal
hot engine) and does not seem to play up much. (this one starts fans / controls
fuelling etc via the PCM) The gauge sender is around 100 ohms (normal hot
engine) and is required to go practically short circuit for an overheat
condition. This sender only operates the temperature gauge but its analogue
output is digitised in the instrument cluster for obd reporting. (this is the
temperature signal available in the instrument reset
This sensor has a habit, after a few years, of going intermittent or high in
value giving rise to low readings on the gauge. To test the gauge remove the
plug from the sensor and push a 100 ohm resistor into the plug. This should give
a normal mid scale reading on the gauge. A wire link inserted in the plug should
give full scale hot. Obviously left disconnected the gauge should remain at
However the problem described was not so much sensor failure but a fault in the
Instrument Cluster which can be diagnosed by taking the plug off the temperature
sensor and checking the temperature display in the instrument reset mode.
Roger had found this problem earlier and offered the solution along with the
photos below :-
"There are two solder joints on the circuit board that are very close and if the
solder is a bit on the large side the two 'blobs' make contact. You may find it
happens more in winter or cold spells when the board contracts. One member had
reported that when the lights were on the gauge behaved itself - believe it or
not that was due to the dash panel bulbs warming the circuit board so that it
expands. Unbelievable but true!
The fix is to remove some of the solder from the joints. but the dash is a bit
of a pig to get out."
For advice on dash removal see here
Although the Instrument Cluster is a non serviceable item - careful dismantling
can enable a repair to be applied saving a lot of money - but do this entirely
at your own risk.
This shows the solder joints that are at fault - poor soldering in the factory
results in excessive solder on the joint and the close proximity to the other
joints results in a short circuit.
Here you can see the indentation caused in the other half by the excessively