Heater runs but blows cold air?

The friendliest place on the web for anyone with an RV or an interest in RVing!
If you have answers, please help by responding to the unanswered posts.
See posts with no answers
C

CanadianMaple

Active member
Joined
May 6, 2011
Posts
26
We bought our tent trailer (used) in May and took it out for  our first (5 day) trip on the coast.  We had an amazing time, but one night was chilly with the tide coming in.  We went to turn on the heater with the thermostat, it ran but never blew warm air.  Any ideas what could be wrong or what we could check?  The fridge, lights, water pump, etc works great.    We don't have the propane or battery hooked up since we didn't use them.  Do we need propane to run it, I assumed it was electrical.

We live in Canada and will likely need the heat if we plan on camping until September.  When we bought it, that was one thing we didn't check.  It turned on and we kept talking and checking everything out. 
 
haha  That would make sense then.  So, the blower would be electric but the actual element/heater is run by propane, right?

Thank you.  :)
 
It has a burner unit similar to the one in the bottom of a gas oven or Barbecue, but the flame is vented outside. The flame heats up the box it's contained in, and the fan blows air across the box and into the vents.


Kind of a rough explanation, but you get the picture.


Joe
 
It totally makes sense now!  I have no idea why we didn't consider that.  Thank you.
 
The furnace fan (blower) is powered by 12v, so it needs either battery or shore power (via the battery charger/converter) to run. The heater itself is heated with a propane flame, so you need the LP gas to have heat.
 
Hi,
A little off topic, but you really should leave the battery hooked up even if you're using the converter for 12V power. The battery acts as a filter for the converter output. Without it you may get very dirty power and could damage some electronics.
Ernie
 
I will describe the start sequence for a DSI (Direct Spark Ignition) furnace and note possible problems

1: T-stat calls for HEAT (it's cold in her Furnace warm me up)
2: Fan starts (Low battery will cause fan to run slow, no battery may also do this if it has to rely only on a small converter)
3: Sail switch closes (Bad switch, or obstructed air passages not letting air sail past fast enough)
4: Mother board opens gas valve (Bad board, bad valve, clogged orifice (Spider nest)
5: Sparke generator is started by Mother board (In fact it's part of mother board, bad board, bad element (points) spacing,, I actually had this, they were too far apart)
6: Burner ignights (No propane?)
7: Flame sensor sends "I'm hot" to mother board (Bad sensor, bad flame (See clogged orifice) bad board)

RV gets warmer

In addition insect nests in the burner flues can cause issues.

Bad connections in assorted places can do it too.
 
Many (most?) tent trailers have a pilot light ignition on the furnace rather than DSI.

CanadianMaple: What brand/model of furnace is it? Do you have an owner manual for it? You may need further info on how to light your furnace once you have the gas hooked up again.
 
With a pilot light the sequence is still a bit different, The first three steps are the same however, but step 4 is a bit different. it's combined with a later step.. The flame sensor

In a pilot light type there is a flame sensor for the pilot, it signals "Ready" to the control system (Depending on the unit this may be in a couple of different places) often there is a button you must push to light the pilot, if the flame sensor is not hot enough for whatever reason the main burner is supposed to remain "locked out" by the safety valve it commands.

In this case the two burners (Main and pilot) orifice nozzles are my prime suspects.  Then the valve and sensor.
 
I'm out camping now with sketchy wifi, so I will post again when we're home on Monday.  I'll see if I can gather the info in the meantime.  I really appreciate your help.
 
CanadianMaple,

Dirty power is a term for a noisy signal. When the Converter changes AC to DC, it does so by first reducing the voltage with a transformer (to about 12 Volts) and then rectifying the AC with diodes. A diode is a device that only conducts one way and by doing so converts Alternating Current (flows both ways alternately, changing direction 60 times per second) to Direct Current (only flows one way). Rectifying the AC, since this is not a perfect world, results in a pulsating (noisy) DC rather than smooth current flow as you get from a battery. Some of the pulses can be quite high in amplitude; why is a little complicated and I won't go into it here, but the blower motor is partly responsible even when running off the battery.

Connecting the battery allows the battery to smooth out the current (filter the pulses) so that the pulses are reduced or even eliminated (for practical purposes). This happens because the battery charges during the high pulses and discharges during the lower voltage periods thus averaging out the voltage.

More than you ever wanted to know probably, but there it is:Hope it helps you understand.

Regards,

Ernie


 
You must log in or register to reply here.

Latest posts

Members online

Total: 757 (members: 36, guests: 721)

Forum statistics

Threads
131,914
Posts
1,387,314
Members
137,666
Latest member
nativoacai
Back
Top Bottom