AC Rest Button Function/s

I noticed if I start my furnaces before/while driving and depress the AC rest button (with the fan speed on low) before I turn the engine off, the dash fan will continue to blow warm are (as long as the engine is warm enough?). I sat and waited ~20min for it to shut off and it never did.

Has anyone with a factory Espar furnace seen this occur?

I don't think the REST engine-off heat function necessarily requires a factory Espar heater, what it does is run a small pump to continue to circulate coolant between the block and heater core so as to provide heat after a warm engine has stopped (the heat comes from residual engine heat, not the Espar, although some models can be optioned to use the Espar as well.) The residual engine heat-only version does shut off after a certain period of time but I've never timed mine.

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This is astounding since IINM it's labeled AC rest. It makes my furnaces MUCH more effective!

smiller said:

... The residual engine heat-only version does shut off after a certain period of time but I've never timed mine.

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I recall somewhere in T1N literature seeing 20 minutes. On my T1N's (I don't own an NCV3) the REST timeout is at least 20 minutes... not longer than 30 minutes. On my 2006 T1N with Auxiliary Heater Timer Control, REST, and BOOST mode, the Espar heater doesn't operate when REST is engaged.

Originally I was surprised to see BOOST included with the Aux Heater Timer Module. When the Espar heater is enabled using the Timer Module controls it will ride through an engine start and continue to run after engine shutdown (subject to the timer interval). In BOOST mode the Espar heater engages with engine running and shuts down with engine off.

Not all of the above may apply to an NCV3, but my guess is that the basic design premises and logic hasn't changed significantly.

vic