What switch for manifold heater?

[ekmoor]

So my 1700B has a push bottom near the ignition switch to heat up the manifold for cold weather starts. My recently acquired 1400B does not have this push button. Any idea on how to actuate the manifold heater? Looking at the manual, it says the ignition switch but my switch does not have this feature.
Sorry for rookie question.

[hair bear]

Put a test light or voltmeter between the heater supply lead and battery earth. Turn the key slowly and somewhere between 'ign on' and 'start', you may see the light come on or a current register. If not, try turning the key backwards, see if that does anything.