Aqua hot furnace blows cold air

[Neveucamp]

should the aquahot furnace in my 2020 phaeton be able to heat the coach in way below freezing temps?
Witerized and connected to shore power. Full diesel in tank.

Furnace comes on. Fan comes on (set to auto). Only blows cold air. Set to use diesel.

[outlawten5]

Should easily heat the coach to any temp you want on Diesel burner

[Warhorse6]

Have just left 3 days in 20 degree temperatures. Obviously heat pumps in Roof units don’t work. Electric heater marginal effective heating to low 60s inside. Heated floors on with aqua hot on diesel heat the solution to comfy temps in 70s. Aqua hot worse case 1/2 gal of diesel per hour.

[weighit]

yes the Aqua hot will heat the coach, if your getting cold air from a set of registers, maybe that pump is not pushing the hot fluid. There are a couple of pumps and you eed to verify they are operating.

[chuckftboy]

There shouldn't be any cold air blowing. The fans on my hydronic coils don't run until the coils are warm from hot water flow.

[tmann45]

I recently had this problem on my smaller single loop Aqua Hot.
Everything appeared to be operating correctly, but only cold air discharge from registers. Tank hot, hot water available, loop pump running.
Some suggestions I got were stuck check valve (single loop does not have check valves), vapor/air bubble lock, 3-way way valve stuck closed.
Only slide with registers was in, extended slide and got heat out of resisters.
My assumption is that hose was crimped with slide in blocking boiler fluid flow.
There are trouble shooting steps in manuals, like control board lights to check.

[oldeguy]

My 450D register Fans energize once radiator is hot, then it blow hot air.