Reply
 
Thread Tools Search this Thread Display Modes
 
Old 05-31-2019, 05:57 PM   #1
Member
 
Join Date: May 2011
Posts: 6
Question Intermittent Attwood 7916-II Furnace

Our 2007 TowLite's Attwood 7916-II furnace failed a while back, because of bad bearings, so we replaced the motor. It worked fine for ~10 hrs of actual operation, but is now failing intermittently. For example, when we set the thermostat and bed down at night, it later clicks on when the temp goes down, and the unit comes on, and all is good. This cycle repeats 3, 4 or 5 times, but then it stops, and we freeze for the rest of the night.

The next AM I remove the bed that's over the furnace compartment, remove the compartment lid, remove the furnace cover and find that the toggle switch (breaker button) is now "OFF." So, I flip it to "RESET" and the unit then fires up, good as new, until the next night, when it fails in the middle of the cold night and we freeze, because I will NOT tear my bed apart to go after that toggle switch at 3 AM. I'd rather freeze. My wife is not happy.

The compartment and furnace unit are very clean, and there's nothing blocking the intake or exhaust vent openings, so I don't know where to start. I've read over various posts on this forum about sail switches, and I've found on-line a bunch of inexpensive parts available for this unit, but I have no idea how to start troubleshooting an intermittent problem. I've attached photos of the furnace cover, furnace with uncovered furnace with black toggle switch, thermostat and intake vent, which probably are of no help, but there they are...

I'm appealing here for your best guesses on what to replace first, then second, then third,....!

Thanks in advance!
Attached Images
File Type: jpg Furnace Cover.jpg (183.0 KB, 5 views)
File Type: jpg Furnace Toggle Breaker.jpg (215.3 KB, 11 views)
File Type: jpg Furnace Thermostat.jpg (157.6 KB, 5 views)
File Type: jpg Furnace Intake.jpg (206.5 KB, 5 views)
__________________

Lou M is offline   Reply With Quote
Old 05-31-2019, 07:07 PM   #2
Site Team
 
JackandJanet's Avatar
 
Join Date: Jul 2010
Location: Pine, AZ
Posts: 2,962
Default

Lou - I feel for you. Intermittent problems can be infuriating.

I'm not clear about something from your post. The second night the furnace stopped working, was the "reset" switch again off? If so, that would indicate to me an electrical problem that is seen as a heavy draw. Now what would cause that heavy draw could be the motor or bearings again. There's not much else in there that's powered by electricity. It's also possible the reset switch itself is bad, and has become too sensitive to the starting current draw when the furnace fan starts.

If you move the fan by hand, do you feel any resistance? That would indicate a bad unit, which seems improbable since you just replaced it, but still .... Just looking at the thermostat, I don't see any way to set it to "fan only", which would be a way to help troubleshoot.

I suppose if the furnace failed to light, there may be a safety feature that would trip the reset switch, but I've never had any problems with mine, so I can't give good advice here. Perhaps someone else might have some thoughts. I do know that something as minor as a few spiderwebs can interfere with successful lighting.

Good luck!

- Jack
__________________

__________________
Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH
2014 F150 Platinum 4x4 3.5L EcoBoost SCrew
JackandJanet is offline   Reply With Quote
Old 06-01-2019, 10:38 PM   #3
Member
 
Join Date: May 2011
Posts: 6
Default

Yes, I flip the switch to "RESET" the next day before bed, and same story in the night: it flips to "OFF" after a few cycles. I like your idea that it needs a new toggle switch, because it may have become worn (and more sensitive) to current surges during its previous life with a motor having bad bearings. It's easy to try too.

I can look for spider webs on the sail switch too.

Thanks Jack.
Lou M is offline   Reply With Quote
Old 06-01-2019, 10:55 PM   #4
Site Team
 
JackandJanet's Avatar
 
Join Date: Jul 2010
Location: Pine, AZ
Posts: 2,962
Default

Lou - I think if gunk like spiderwebs were causing the problem, they'd be around or in the burner outlets, or the inlets for where air is added to the propane feed, not the sail switch. That was the cause of an issue with a patio heater I had once and it was a real problem to correct. It takes very little to upset the proper air-fuel mixture ratio.

But, if you can see the burner flame when the furnace is on, I think it should be a blue color, with very little yellow. This is a guess, however, since I've never looked at mine. My patio heater's flame had turned from a vigorous clean blue flame to a "lazy", smokey, yellow one. Maybe someone would confirm this for us. If the flame is blue though, its mixture is good and the problem just about has to be in the blower circuit.

- Jack
JackandJanet is offline   Reply With Quote
Old 06-07-2019, 09:30 AM   #5
Junior Member
 
Join Date: Mar 2018
Location: Fish Haven, Idaho
Posts: 2
Default

Get a new igniter. I have the same furnace in another rv. Did the same thing and was tough to diagnose until I inspected the igniter under a magnifying glass and saw a hairline crack that was allowing the igniter to ground out intermittently and fail to spark...thus throwing the furnace into fault mode for failure to light fault
Tomrupp is offline   Reply With Quote
Old 06-07-2019, 09:53 AM   #6
Site Team
 
JackandJanet's Avatar
 
Join Date: Jul 2010
Location: Pine, AZ
Posts: 2,962
Default

Hi Tom, and welcome! That sounds like good advice. It's certainly something to keep in mind when furnace problems crop up. Lou, if you're still having the problem, check out the igniter.

But, I don't see how this would trip the "Reset" switch - that symptom brings me back to the blower.

- Jack
JackandJanet is offline   Reply With Quote
Old 06-07-2019, 10:06 AM   #7
Junior Member
 
Join Date: Mar 2018
Location: Fish Haven, Idaho
Posts: 2
Default

Hi Jack, thanks for the welcome. I had put in a new sail switch and control board to solve my problem. Then I found the igniter issue. Problem solved. If you are going to "shotgun" parts by replacing like I did, start with the igniter. It is by far the easiest and cheapest to replace. I wasted about $100 before I changed the igniter. And when it fails the furnace will attempt several tries at ignition. I think it was three times on mine. Then when it senses "Non detect" on the actual burner flame it goes in failure mode requiring a manual reset. Just saying, check the easy and cheap stuff first. But for expensive and not so easy I'm heading out in the driveway now to replace all four lift cables. 1985 FunChaser 21L
Tomrupp is offline   Reply With Quote
Old 06-07-2019, 02:14 PM   #8
Site Team
 
JackandJanet's Avatar
 
Join Date: Jul 2010
Location: Pine, AZ
Posts: 2,962
Default

Tom, thank you!! That's excellent information! I had no idea the igniter could cause the Reset switch to flip. With this in mind, Lou - since you replaced your blower, I now think the igniter is the next thing to look at.

- Jack
__________________

JackandJanet is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


» Featured Campgrounds

Reviews provided by

Powered by vBadvanced CMPS v3.2.3
Disclaimer:

This website is not affiliated with or endorsed by Hi-Lo Trailers Worldwide or any of its affiliates. This is an independent, unofficial site.


All times are GMT -5. The time now is 02:08 AM.


Powered by vBulletin® Version 3.8.8 Beta 4
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
HiLoTrailerForum.com Copyright 2010