Cylinder Head Temperature Gauge, Yak 52, Yak 50, Yak 18-T, Yak 55, Sukhoi
This CHT gauge is used on nearly all aircraft fitted with the Vedeneyev M14 series engine.
This works in conjunction with the Cowl Flap lever, alerting the pilot to adjust the Gills to keep this needle in the Green range.
This gauge is driven by a thermopile that resembles a Spark Plug washer. For the Yak 52, there is one CHT gauge in each cockpit, and the thermopiles are usually under number 7 and number 4 spark plugs.
These thermopiles generate a very small voltage - in the 2 volt range. (For this reason you'll get CHT readings after shutdown, with all electrical power off.) The thermopile assembly is a separate unit, which connects by a stout, low resistance copper cable to this CHT gauge.
For corresponding CHT readout in both cockpits, conductors' lengths ( resistance) have to be closely matched. For this reason the distance to the rear cockpit determines how long both interconnecting cable must be. This means excess length for the front cable gets coiled up and strapped to the upper engine mount - see picture.
If you experience intermittent signals ( a swinging or lagging needle) in the front cockpit, this coiled up wire is a great place to start looking for chafed insulation, because even a small ground can have a large effect when 2 volts is the maximum output.
The Canon plug on the rear should be safety wired.
If you are having CHT readout problems in your Yak 52, switching gauges between front and rearcockpits will eliminate doubts over gauge or the above mentioned grounding problem.