410 Air Conditioning

[Roger Morrall]

Originally Posted by David C

I had a look at the 411 wiring diagram to see how Bristol changed the wiring as more toys were added and current consumption increased. An interesting anomaly to my understanding is that the 411 engine fans are fed directly from the battery if controlled by the Otter thermostat but through the ignition switch in manual override.

Seems to me to be unlikely, the comparatively unsophisticated wiring-wise 410 already had a relay mounted under the bonnet that had parallel trigger inputs from the otter switch and the over-ride switch and I believe the (later?) 411 wiring and fusing arrangements were further improved. So the load isn’t actually taken directly by either the otter switch or the ignition switch

Originally Posted by David C

Unless anyone can give me a good reason I think I will keep that sort of load away from the ignition switch.

I alarmed myself considerably when I tested and added up all the other potential loads on the poor little ignition switch (the windscreen wiper stall current on a dry windscreen was particularly amazing) and rearranged things so that the ignition switch drove a very heavy duty relay (sometimes known as a contactor) to take those loads.