Furnace blows cold air - Page 2

guy99 · 03-02-2007, 04:22 PM

Quote:

Originally Posted by overlander63

Now, for MY stupid question, did you turn the propane on before trying to run the furnace?

If you mean at the tank, yes. Stove works, gas hot water heater work. The furnace worked fine last night but this morning it started blowing cold air.

guy99 · 03-02-2007, 04:24 PM

Quote:

Originally Posted by TomW

Do you hear the electronic ignition "clicking"

Tom

No, I don't hear any clicking but the blower is running so I'm not sure I could hear a soft click.

guy99 · 03-02-2007, 05:03 PM

RV tech just left. (Since we need to live in the rig until next week I decided that I'd let a pro with a good supply of parts have a go)

He replaced the limit switch and it seems to be working. As he was poking around checking continuity of the limit switch, the burner lit. After that, it seemed to be working. He recommended replacing the switch saying often his customer won't replace the switch after it starts working and end up calling him back in a few days.

So we are the proud owner of a new limited switch and a working furnace (at least for now).

GlenCoombe · 03-02-2007, 05:22 PM

Very cool....er ... warm. Glad you got that sorted. I wish I had propane onboard. The one thing the old Coachman could do was run you out of the bus with the Suburban furnace.
The electric heat on Airstream One is o.k. but not for boondocking.
It's on the list, just a little ways down in priority.

zamboni · 03-02-2007, 06:58 PM

I sure wish AS er...suburban would come up with a furnace that could use electric (when plugged in) or propane when boondocking. We have a heat strip in the roof air, but our roof air is original and kinda noisy to run all the time in winter...os we use the "propain" furnace. It sure heats up the MH.

lewster · 03-02-2007, 07:15 PM

Quote:

Originally Posted by guy99

RV tech just left. (Since we need to live in the rig until next week I decided that I'd let a pro with a good supply of parts have a go)

He replaced the limit switch and it seems to be working. As he was poking around checking continuity of the limit switch, the burner lit. After that, it seemed to be working. He recommended replacing the switch saying often his customer won't replace the switch after it starts working and end up calling him back in a few days.

So we are the proud owner of a new limited switch and a working furnace (at least for now).

You made the right move in having it serviced by a qualified professional. The electrical path that allows the electrode to fire starts at the battery, thru the sail switch, (normally open, also called an air-prover switch) then thru the limit switch (normally closed) and into the igniter board. The board then will send a spark to the electrode as it opens the gas valve, and the burner ignites. It usually tries this 3 times before shutting down if it does not ignite (newer furnaces with DSI feature).

If any part of this path is blocked due to a failed component..... 'ya just don't get no heat!!!! (as in your open limit switch).

balrgn · 03-02-2007, 07:53 PM

Quote:

Originally Posted by guy99

RV tech just left. (Since we need to live in the rig until next week I decided that I'd let a pro with a good supply of parts have a go)

He replaced the limit switch and it seems to be working. As he was poking around checking continuity of the limit switch, the burner lit. After that, it seemed to be working. He recommended replacing the switch saying often his customer won't replace the switch after it starts working and end up calling him back in a few days.

So we are the proud owner of a new limited switch and a working furnace (at least for now).

Very nice, peace of mind!

guy99 · 03-02-2007, 08:17 PM

After the RV Tech left, the heater worked normally for a while but it was a bit too warm so Marian turned the heat down. A while later she felt cold so turned the thermostat up. The furnace fan started and blew cold air ... I called the RV Tech and he came right back. Replaced the igniter and things seem to be OK. We turned the furnace down and went out to dinner, just returned and the furnace fired up and provided heat. So far so good.

I sure wish there had been a more definitive diagnosis so that I had more confidence in the 'fix'.

Oh well, time will tell.

Tim A. · 03-02-2007, 08:48 PM

We have been among the unlucky few who have had our furnace blow cold air any number of times. The first time it was the igniter (control) board, the second time it was the sail switch, the third time it was a failing gas regulator which reduced the gas pressure, and the fourth-fifth-sixth-etc. times it was the sail switch. Most of these occurrences were underway, of course. I have become expert at taking the furnace out and reinstalling it. This is not a process to be taken lightly, because of the gas lines. Needless to say, I have been very, very careful.

When the cold air problem now arises, I have finally learned to bang on the side of the furnace (I have an access hole) where the sail switch is located. Gets the darn thing to work every time! We still have a spare sail switch and ignition board with us just in case. Oh, also a nice electric space heater.

Rob30044 · 03-02-2007, 10:12 PM

My furnace was blowing cold air too. I was getting 12 volts at the gas valve and the valve was opening. I replaced the ignitor board today. I HAVE HEAT!!

Ben

lewster · 03-03-2007, 06:36 AM

I check on a furnace call is the igniter board. Any RV tech ain't worth salt unless they carry an igniter board tester. It's the only way to tell if the board is working properly. The same board is found on lots of LP appliances other than furnaces....like water heaters and refers too.

After the board is determined to be working, the rest of the components are checked and I will often find more than one problem. I always try to get it done right on the first trip.

guy99 · 03-03-2007, 10:13 AM

Quote:

Originally Posted by lewster

I check on a furnace call is the igniter board. Any RV tech ain't worth salt unless they carry an igniter board tester. It's the only way to tell if the board is working properly. The same board is found on lots of LP appliances other than furnaces....like water heaters and refers too.

After the board is determined to be working, the rest of the components are checked and I will often find more than one problem. I always try to get it done right on the first trip.

Lew,
My wife says that if everyone was as professional and competent as you, the world would be a better place.

The fellow who came to work on my furnace seemed like a nice enough guy but it seemed like he didn't really want to be working Friday afternoon. He must have told me five times that he wanted to avoid taking the furnace out. I asked about the sail switch and the igniter board but he said he hoped it was something else because he would have to remove the furnace to get to the board and sail switch.

Maybe we lucked out since the furnace IS working this morning.

eubank · 03-03-2007, 12:04 PM

Ok, I think we have the makings of a nice bet here.

I SHOULD have bet on one last month! We had some of our crew of retiree skiing guests here at the park with a non-functional heater. From the symtoms, I said sail switch; others of the crowd said otherwise. They took the rig down to Albuquerque for repairs, and it was indeed the sail switch. (On the other hand, I struck out completely on a different rig last month, too, so my confidence was a bit shaken.)

So what about a bet anyway. I'll say it's the sail switch. Others can say something else. Whoever loses will send five bucks to Andy in support of the forums!

Lynn

crestonrv · 03-03-2007, 10:10 PM

i find interesting things with furnaces-mouse in squirrel cage,cat hair binding sail switch,vermin chewed wiring,blocked ducts(causes high limit to kick)found a snake skeleton once .anyway best way to fix furnace is to do annual service as recomended by manufacturer.i used to think it was a gimmy for serv.center but i have a customer (1 out of 3500+in my files) who does all his recomendeds every feb. and we have yet to see a problem with his appls.his coach is four yr old diesel pusher we have had other prblms but no appls. note he is on the road avg. 8 months a year.