QUESTION.
I am concerned about about my Lotus Excel SE engine over-heating as the radiator fans do not turn on until the dash gauge indicates the water temperature is at 95 degrees Centigrade.
Are the fans turning on too late because of a faulty switch and will this cause my Lotus 912 engine to over-heat?
P.H. - Melbourne, Australia
ANSWER.
Before condemning the radiator fan switch as being faulty, there are some hidden factors to be considered.
From experience, the Excel temperature gauge and transmitter have often proven to be inaccurate when checked against a quality instrument.
The temperature gauge can easily checked by using a hand-held infra-red thermometer or better still a FLUKE DVM with a thermo-couple adapter (temperature probe)
The engine should be started and allowed to warm up to normal operating temperature and measurements made at the thermostat housing.
From experience, Lotus Marques has observed dashboard temperature gauges reading too high by 8 to 10 degrees Centigrade.
To illustrate the point, the dashboard gauge may indicate 95 degrees Centigrade but the thermostat housing temperature may give a true reading of 85 degrees Centigrade - this is a common error and fortunately the gauge will usually read high and hopefully prompts the driver to take action!
The only way to try and correct this error is to change the aging temperature sensor.
Check the temperature transmitter by carrying out DC resistance measurements with a DVM.
The resistance at 18 degrees Centigrade should be between 800 to 1200 Ohms.
The resistance at 85 degrees Centigrade should be between 100 to 120 Ohms.
Once the temperature gauge has been checked, then the radiator fan switch operation can be checked using a hand-held infra-red thermometer.
Be aware both the temperature sensor and radiator fan switch are subject to manufacturing design tolerances.
Once the engine is started both components are in constant use and will not last forever.
For more information regarding trouble shooting cooling system problems, see the comprehensive documention in the technical information section on this web site.
Copyright © 2012 Lotus Marques
I am concerned about about my Lotus Excel SE engine over-heating as the radiator fans do not turn on until the dash gauge indicates the water temperature is at 95 degrees Centigrade.
Are the fans turning on too late because of a faulty switch and will this cause my Lotus 912 engine to over-heat?
P.H. - Melbourne, Australia
ANSWER.
Before condemning the radiator fan switch as being faulty, there are some hidden factors to be considered.
From experience, the Excel temperature gauge and transmitter have often proven to be inaccurate when checked against a quality instrument.
The temperature gauge can easily checked by using a hand-held infra-red thermometer or better still a FLUKE DVM with a thermo-couple adapter (temperature probe)
The engine should be started and allowed to warm up to normal operating temperature and measurements made at the thermostat housing.
From experience, Lotus Marques has observed dashboard temperature gauges reading too high by 8 to 10 degrees Centigrade.
To illustrate the point, the dashboard gauge may indicate 95 degrees Centigrade but the thermostat housing temperature may give a true reading of 85 degrees Centigrade - this is a common error and fortunately the gauge will usually read high and hopefully prompts the driver to take action!
The only way to try and correct this error is to change the aging temperature sensor.
Check the temperature transmitter by carrying out DC resistance measurements with a DVM.
The resistance at 18 degrees Centigrade should be between 800 to 1200 Ohms.
The resistance at 85 degrees Centigrade should be between 100 to 120 Ohms.
Once the temperature gauge has been checked, then the radiator fan switch operation can be checked using a hand-held infra-red thermometer.
Be aware both the temperature sensor and radiator fan switch are subject to manufacturing design tolerances.
Once the engine is started both components are in constant use and will not last forever.
For more information regarding trouble shooting cooling system problems, see the comprehensive documention in the technical information section on this web site.
Copyright © 2012 Lotus Marques
