Furnace blowing but no heat. Help please!!!

[coairstream]

I have a 1987 290 motorhome that I'm shivering in right now We've only owned her since the 22nd and had this problem the only other night we were boondocking as well. Here is the problem:

At about 2am my girlfriend got up to use the restroom and the pump was taking a long time to get pressurized so it woke me up. I also noticed it was extremely cold but the heater fan was blowing with no hot air. I cycled the thermostat on and off a few times and adjusted the temperature with no success. I checked the battery level on the monitoring system and its showing low but things seem to never working ok. The only other night this happened was when we were not plugged in and it kicked back on either after I let the generator run a while to charge something up to get the furnace to ignite or I messed with the thermostat that somehow kicked the igniter back on.

The thermostat is probably more probable but it happening again while not plugged in is what makes me think low battery might have something to do with it? Generator hours are not until 8

Thanks in advance.

[TG Twinkie]

Low battery is most likely the cause.
If all works well when the generator is running it's most likely you don't have enough battery capacity, the battery is bad or not charging properly.

[coairstream]

Thanks TG! I'm counting down the minutes until 8am to give it a shot! If the batteries have enough juice to run the lights, water pump, heater blower, etc. wouldn't that be enough to ignite the furnace? This one is really confusing me.

[HowieE]

Check the voltage with a meter.

If it low the fan may not be spinning fast enough to switch the sail switch to the on position.

[idroba]

Almost certainly low battery voltage is causing your problem.

[Airline]

Low Battery For Sure.

[xrvr]

Fire up the mh and see if that helps.

[coairstream]

Gentlemen we have fire! The generator kicked it on. Must be that sail switch thing? Kinda seems like a bad design. My final destination is Colorado so I'm thinking I'll get a 12 volt ceramic heater as a back up. Thoughts?

Oh one other thing I left the roof vent open so I bet the heater was running non stop! No wonder I ran the battery's down.

[xrvr]

If you have a bad battery, the only way to solve your problem is to replace it. Running a 12 volt heater will kill the battery pronto, quicker than running the furnace.

[UKDUDE]

Don't know what it's like on a 290, but on my Interstate, the propane supply is protected by a solenoid that is electrically held open. So when your batteries die, the solenoid closes and the propane is shut off.


Sent from my iPhone using Airstream Forums

[ShinyPete]

UKDUDE just said what I was fixin too............ Meter your batteries and if they're low when not being charged with any method, there's your culprit. Even if the sail switch closes, you're not getting LP flow due to low voltage, so no fire........... It seems like I also helped a neighbor determine his LP detector went bad (but didn't alarm) once and that shut off his LP flow too, so fan blew but no fire...........

I don't know that coach but I bet you have more than one "house" battery. May be two 12vs or 2 6vs or even 4 6vs......... Check your battery compartment to be sure, and if you replace them, take a picture of how they're wired together, because you won't remember when you go to put them back.

Hope this helps!

[kdickinson]

If you plan to boon dock in cold weather definitely get back up heat sources because furnace fans use a lot of battery power and in my trailer we found that it depletes the battery in 3 - 4 hours at which point the temp inside will become = the temp outside over the following 5 - 6 hours. We bought a Camco catalytic heater and installed a quick LP connect off the furnace supply line. That is our back up heat source for when we are not connected to shore power. This heater does not require electricity to run and it is only limited to the amount of LP you have on board.

[cazual6]

If replacing a battery, I suggest the AGM, a little pricey, but worth the price. Also consider Solar if within your budget.

[idroba]

Originally Posted by coairstream

Gentlemen we have fire! The generator kicked it on. Must be that sail switch thing? Kinda seems like a bad design. My final destination is Colorado so I'm thinking I'll get a 12 volt ceramic heater as a back up. Thoughts?

The sail switch is a safety feature as part of a good design. If the fan is not running, or is running too slow to remove the heat produced by the burner, it shuts the unit down.

If you mean you are going to get a small 120 volt (not 12 volt) heater, that is not a bad idea. But not a 12 volt heater, you need no more load on your battery system.

[HowieE]

Your ONLY option for an aux. heater while boondocking is a propane catalytic. Even with low batteries the interlock on the propane tanks should remain open because of the very low current they take.

You want to check your batteries with a hygrometer not just a voltmeter. If any cell is low replace all batteries as the poor one will draw down the others.

[3wd67rg]

Originally Posted by HowieE

Your ONLY option for an aux. heater while boondocking is a propane catalytic.

What he said.

Chris and I are buying one of these from my daughter.

http://www.amazon.com/Mr-Heater-F232...+space+heaters

[AldeanFan]

Pretty sure i saw this heater on sale at bass pro this week, might have to pick one up

[dtshasty]

If not your battery, check this page on troubleshooting the heat system.RV Daily Tips Issue 782. Dec. 29, 2015 | RV Travel

[Mike1997]

Found your furnace problem interesting. Something similar happened with my 97 Landyacht on arrival in Montana in October. Only had it since April and it spent entire life in the south on short trips to Florida and along the coast. Because it also has heat strips in the roof units, the furnace was never used. Blower would activate but the furnace would only run about 5 seconds. Kept doing this over and over. Had a wonderful Mobile RV Tech come to the campground and he found the computer board in the furnace was defective. $130 later it was working like a charm with no problems since. Lesson learned was just because it was never used, its still 17yrs old. This lesson also applies to tires that look great but are old.......replace them or else!

[coairstream]

Update: The batteries were from 2008. Thanks to everyone's post I bought two new and problem solved!