Cylinder Head Temp Gauge - 64 Spyder
Cylinder Head Temp Gauge - 64 Spyder
Where exactly would I find the thermister wire that is connected to the engine ?
Re: Cylinder Head Temp Gauge - 64 Spyder
Under cylinder #3 right center. Then runs to a plug in the rear of the engine harness by the coil wire.
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- bbodie52
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Re: Cylinder Head Temp Gauge - 64 Spyder
The sensor that is mounted in the right cylinder head is a cylinder head temperature unit, but it is a simple switch that only provides a ground if the engine reaches a temperature that is high enough to be considered to be an overheat condition. It shares a wiring harness that is connected to the oil pressure sending unit switch which is located just to the right of the generator. A ground on either one of the switches will cause the TEMP/PRES warning light to illuminate. The oil pressure warning light switch defaults in a "closed" condition (when there is no oil pressure). This provides a ground before starting the engine to test the warning light when the key is turned on, but before the engine has been started. When the engine starts and oil pressure reaches the warning switch, the switch opens which removes the ground and turns the oil pressure warning light off. The temperature switch in the right cylinder head is never closed unless the engine overheats. I have been driving Corvairs since the 1960s and I've yet to see that warning light come on because of an overheat condition.dave t wrote:Sun May 21, 2017 4:02 pm
Under cylinder #3 right center. Then runs to a plug in the rear of the engine harness by the coil wire.
The cylinder head temperature gauge that is found in the Corvair Spyder (1962-1964) or the Corvair Corsa (1965-1966) is connected via a single wire to the thermistor, which is located near the underside front of the left cylinder head. The thermistor looks like a small spark plug. It is a variable resistor that changes resistance value as engine temperature changes. While the switch on the right side is a simple ON/OFF switch that controls a warning light, the thermistor is an analog device that varies resistance along with head temperature changes, which is reflected as a temperature reading on the gauge.
Left-click each image with your mouse to enlarge the image for better viewing… The complex warning light arrangement in the above diagram uses a silicon rectifier (diode) to prevent the warning buzzer from coming on when the warning light is illuminated by the oil pressure warning switch. The audible warning buzzer only comes on if the engine overheats and closes the temperature switch, which would illuminate the warning light AND sound the buzzer.
Brad Bodie
Lake Chatuge, North Carolina
1966 Corvair Corsa Convertible
Lake Chatuge, North Carolina
1966 Corvair Corsa Convertible
Re: Cylinder Head Temp Gauge - 64 Spyder
BBODIE52 is correct. My mistake. The sender on the right is for the light. The thermister in the left head is for the gauge. My bad. Sorry
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Re: Cylinder Head Temp Gauge - 64 Spyder
Brad did a great job of covering the circuit and component location.
Note that the Spyder temperature gauges weren't as accurate as the LM Corsa guage and the thermistor drifts with age. Bottom line - figure out where the needle is during normal operation and if it start going up - beware. By the time the overtemp buzzer and light come on the engine is overheated to the point damage may occur.
Always make sure the FAN/GEN warning indicator illuminates when you turn the key on BEFORE starting.
Note that the Spyder temperature gauges weren't as accurate as the LM Corsa guage and the thermistor drifts with age. Bottom line - figure out where the needle is during normal operation and if it start going up - beware. By the time the overtemp buzzer and light come on the engine is overheated to the point damage may occur.
Always make sure the FAN/GEN warning indicator illuminates when you turn the key on BEFORE starting.