Checking Ignition Change-Over

Connect timing light and tachometer and check ignition timing at idle, should be 5° ATDC. Connect wire of 212°F temperature switch to ground, ignition timing should advance by about 12° and engine speed should increase by about 200 RPM. Reconnect temperature switch wire and switch on air conditioning. This should also advance ignition and raise engine speed by about 100 RPM. If ignition retard is not cancelled, check two-way valve and relay.