Furnace help

I'm going to jump the gun and give you a cheap and easy fix. The reason why is because my neighbor had your setup and after pulling the furnace and going through all the systems it turned out to be this.

Pull the cover off the furnace and you should see the high tension wire. Gently pull that off the sparker and clean the connection. See if that fixes your problems. Could be the Achilles heel of that model.

wa8yxm wrote:
This document is generic for both furnaces and water heaters.. I'm told I missed one possible error..

NOTE: THis is for Direct Spark Ignition Furnaces. If you have a pilot light (I suspect you do not) major mods are needed.

When the T-Stat calls for heat the control board starts the blower (1)
The blower blows closing the sail switch (2)
The control board then opens the gas valve (3) and begins sparking (4.1)
Gas Flows (5) And ignitets (4.2)
The flame heats the flame sensor (5)
The flame sensor sends .480 volts to the control board (6)
which then detects the .480 and continues operation (*)
When the T-stat says "Enough already" (RV is now warm)
The control board shuts off the gas flow (*)
and then turns off the blower after a cool down (*)

*: At nearly every step the control board is involved. IF IT IS BAD, things will not work.. I recommend replacement boards from Dinosaur boards.. When Mine went out the Dino board was less than half the price and when opened the box the quality of construction and workmanship, and then design was very clear to my trained eyes.

1: No 12 volt to furnace, blower motor shot
2: Low 12 volt, air ducts clogged, blower "obstructed" bad sail switch
3: Bad solenoid, Clogged Gas Jet
4: .1: Bad ignition circuit (high voltage) on control board. .2: Points too wide (Very common it seems)
5: These do not often fail but they can
5: Bad connection, NOTE:
5 and * Bad wire.

* applies to all steps by the way So does bad wire/connection.

It appears as if the sail switch has made an early retirement.

I jumped past it today and was rewarded with an immediate spark. unfortunately I was unable to continue troubleshooting due to some personal commitments.



The problem I am having is the sail switch is in the back of the furnace and is behind an exhaust hose that is coming from the front. From what I can ascertain I need to remove the entire furnace from the camper in order to replace the switch.

Is there a way to determine which sail switch is in here without taking the old one out? Just trying to minimize the amount of downtime.

Sail switch is probably just stuck from setting all winter. If possible reach in with something and physically move it back and forth carefully a bit.
Had a furnace that did every spring but after that worked all summer/fall.

Glad I could be of help.. NOW. Just because the sail is not sailing does not mean the switch is toast.

The fan has to blow hard enough to sail it.. (low battery, and the thing I missed is a poor 12 volt connection on the supply side) also if you have heat registers blocked, or say covered with a throw rug or bath mat.. That can keep it from sailing.

But .. At least you now know where to start looking.. Again Glad I could help, thanks for letting us know what it was.


And to the person who said Compairing Pilot light devices to DSI is like a Bread Machine to a rolling pin (you do not use a rolling pin making bread) I agree, which is why I stated the document I published applied ONLY to DSI, not to Pilot Light. Or did you miss that.

Just wanted to follow up..

I had to purchase an inspection camera to see the sail switch. Which happens to be located at the VERY rear of the furnace. a few healthy flicks later and it started working. has been every since.

I know i am going to have to replace this at somepoint in the near future. But at least I have heat during the early season runs.



Thank You

Kayteg1 wrote:
I will not read all long replies here,
but comparing pilot -light appliance to one having ignition/control board is like comparing carburetor car to one having digital fuel control and knock sensor on each cylinder.
Or like comparing rolling pin to bread machine.

:?