Free 7 Day Trial RV GPS App RV Trip Planner RV LIFE Campground Reviews RV Maintenance Free 7 Day Trial ×


Reply
 
Thread Tools Display Modes
Old 02-01-2018, 12:32 PM   #1
Member
 
Join Date: Jul 2017
Posts: 43
Furnace cycles (1sec on, 1sec off, repeat)

2018 Cardinal 3350RL
Suburban SF-42Q furnace

When I start the furnace, squirrel cage starts for 1 second, stops for 1 second, starts for 1 second.... it tries to start 3 times. Then nothing.
All of the forums I’ve reviewed most people at least get the a few minutes before it fails or cycles. Or either get at least 10-20 second until the sail switch shuts them down. No one with a cycle this short.
Any suggestions?
Daniellekristopher is offline   Reply With Quote
Old 02-01-2018, 12:39 PM   #2
Phat Phrog Stunt Team
 
AquaMan's Avatar
 
Join Date: Apr 2012
Location: Tipp City, OH
Posts: 7,154
I would still check the sail switch to make sure it's operational.
__________________
2016 Georgetown 364TS
2017 Jeep Rubicon Recon toad
Nights Camped 2019 - 17
AquaMan is offline   Reply With Quote
Old 02-01-2018, 01:38 PM   #3
Senior Member
 
ejohnson1144's Avatar
 
Join Date: Aug 2017
Posts: 421
Make sure there is no critters in there
ejohnson1144 is offline   Reply With Quote
Old 02-01-2018, 08:24 PM   #4
Senior Member
 
Join Date: Dec 2010
Location: East Berlin
Posts: 732
Has it just started this or is this the first time using it? Are all your other gas appliances working ok? Are you plugged in to shore power? If not are your batteries fully charged? Do you hear the igniter clicking?
Rich5117 is offline   Reply With Quote
Old 02-01-2018, 08:35 PM   #5
Senior Member
 
Join Date: Apr 2016
Location: Port Charlotte Fl/Hinsdale Ma
Posts: 4,823
Quote:
Originally Posted by Rich5117 View Post
Has it just started this or is this the first time using it? Are all your other gas appliances working ok? Are you plugged in to shore power? If not are your batteries fully charged? Do you hear the igniter clicking?
won't start without gas. Stovetop working??
cavie is offline   Reply With Quote
Old 02-02-2018, 01:57 PM   #6
Member
 
Join Date: Jul 2017
Posts: 43
Still not working.
What I’ve done so far....
1) replace the sail switch.
2) searches for critters (none), no dust build-up, but still vacuumed ducts and squirrel cage.
3) measured gas pressure with a homemade tube. 11 inWC. GenSet, Stove, and Gas Water Heater all working great
4). Tried running Furnace while on shore power. Batteries at 13.6V.

The gas does not try to ignite, because blower does run long enough to meet the 15-second sail switch contact (constant flow) call.
Cage spins for 1 second, stops, tries again. Five times (not 3 anymore), then quits until I reset.
Furnace worked great for 6 months. Typical use has been 2 days per week.
Daniellekristopher is offline   Reply With Quote
Old 02-02-2018, 02:38 PM   #7
Senior Member
 
ejohnson1144's Avatar
 
Join Date: Aug 2017
Posts: 421
I would bet it's not igniting Mabe igniter needs adjusted
ejohnson1144 is offline   Reply With Quote
Old 02-02-2018, 02:52 PM   #8
Member
 
Join Date: Jul 2017
Posts: 43
The SF-42Q has a 15-second Purge Cycle before it requests gas. Followed by a 7-second Ingnition & Flame Sense cycle.
Blower never runs long enough to even get close to Ignition cycle.
Daniellekristopher is offline   Reply With Quote
Old 02-02-2018, 02:54 PM   #9
Pickin', Campin', Mason
 
5picker's Avatar
 
Join Date: Aug 2015
Location: South Western PA
Posts: 15,395
I'm just throwing thoughts out...

Have you checked the voltage at the motor when it starts & stops?
I'd be interested to see if you are losing voltage at the motor wires during these 1 second cycles.

If you are losing voltage then you need to find where that voltage comes from. (maybe the control board)

If you are not losing voltage, then you have a bad motor.
__________________
_________________________________________
2016 Flagstaff 8529IKBS Diamond Package 5th Wheel•Goodyear Endurance Tires•2017 Ford F-Series SCREW 4x4•Factory Puck•B&W Companion•TST Tire Monitor w/Repeater•Sinemate 3500w Gen.
F&AM Lodge 358 Somerset, PA - JAFFA Shrine - Altoona, PA

Days Camped: '17=38 '18=49 '19=58 '20=110 '21=116 '22=19
5picker is offline   Reply With Quote
Old 02-02-2018, 03:04 PM   #10
Member
 
Join Date: Jul 2017
Posts: 43
I think you are on the right track. It’s either a bad blower, voltage loss, or bad motherboard.
My assumption is that the 5 quick starts is actually a “fault code”. Which I cannot interprete.
If I get it resolved I will post the solution on this thread to help others.
Daniellekristopher is offline   Reply With Quote
Old 02-02-2018, 06:29 PM   #11
Senior Member
 
Join Date: Dec 2010
Location: East Berlin
Posts: 732
I'll take dibs on on the board
Rich5117 is offline   Reply With Quote
Old 02-02-2018, 06:47 PM   #12
Senior Member
 
ejohnson1144's Avatar
 
Join Date: Aug 2017
Posts: 421
Just for giggles did you try jumping the thermostat out to take it out of equasion
ejohnson1144 is offline   Reply With Quote
Old 02-02-2018, 07:33 PM   #13
Senior Member
 
Join Date: Jul 2017
Location: North of Seattle, WA
Posts: 13,630
I'd see what happens when isolating the motor.

Disconnect it from rest of furnace and with jumper wires apply 12 v directly to it. If it runs continuously without noise or letting out any smoke, the control board is most likely at fault.

If there is any load protection of the circuit board, the one second on, one second off, could be a circuit breaker/short protection cycling due to high current draw by failed motor. Test the motor and get it out of the picture if it works OK.
__________________
"A wise man can change his mind. A fool never will."

"You only grow old when you run out of new things to do"

2018 Flagstaff Micro Lite 25BDS
2004 Nissan Titan
TitanMike is online now   Reply With Quote
Old 02-02-2018, 07:55 PM   #14
Member
 
Join Date: Jul 2017
Posts: 43
I’d like to attempt to “jump the thermostat out”. Attached is a photo of the thermostat wiring. What are the steps?

I will do the Motor isolation & jumper-run tomorrow evening.
Attached Thumbnails
Click image for larger version

Name:	B2A02B3C-EFD6-4C26-8DB5-E203F306AA45.jpeg
Views:	32
Size:	112.2 KB
ID:	161513  
Daniellekristopher is offline   Reply With Quote
Old 02-02-2018, 08:55 PM   #15
Senior Member
 
ejohnson1144's Avatar
 
Join Date: Aug 2017
Posts: 421
Find which two wires go to the funace and jump these wires at thermostat . should start the furnace also was mentioned to check your blower. Should be able to run the fan if you take thermostat out of auto this will test your fan.
ejohnson1144 is offline   Reply With Quote
Old 02-03-2018, 04:31 PM   #16
Senior Member
 
Join Date: Jan 2018
Location: Raleigh, NC
Posts: 5,167
I vote for the power converter board.

Quote:
Originally Posted by Daniellekristopher View Post
I think you are on the right track. It’s either a bad blower, voltage loss, or bad motherboard.
My assumption is that the 5 quick starts is actually a “fault code”. Which I cannot interprete.
If I get it resolved I will post the solution on this thread to help others.
I just saw this same symptom a few weeks ago. It turned out to be the converter (makes 12v DC from 120v AC). You can prove this by turning off the furnace and putting an equivalent load on the converter by turning on a lot of lights. When you do, they will blink at the same 1-second rate.

Larry
Larry-NC is offline   Reply With Quote
Old 02-03-2018, 04:37 PM   #17
Senior Member
 
koller1509's Avatar
 
Join Date: Apr 2017
Location: Jefferson, PA
Posts: 432
You may want to check your high temp limit switch. I had the same trouble once and the switch was stuck open. Try to jumper it out.
__________________
Larry
2014 Ram 3500 Dually 4x4 6.7 Cummins
2017 Sandpiper 378FB
koller1509 is offline   Reply With Quote
Old 02-05-2018, 09:10 PM   #18
Member
 
Join Date: Jul 2017
Posts: 43
QUICK UPDATE: the thermostat could not be jump-tested as it only has three wires which feed a relay module (which is hidden somewhere; with what appears to have lots of in/out wiring on the manual diagram). HOWEVER, I re-initialized the living-room thermostat and associated relay module. The Dometic CT thermostat operating manual suggests that owners Initialize the thermostat(s) EVERY TIME the RV is moved. Furnace works now!! Ejohnson1144 wins... if we’re playing price-is-right rules.
From reading forums, this has also helped people with other issues (AC, Heat Pump, temperature dead band, quick cycling).

Below are the steps to reset the Dometic single zone thermostat....

“System Initialization:
A system initialization will need to be performed by the installer after the system is installed.
• Make szure the Single Zone LCD thermostat is in the Off condition. See page 4, “Quick Reference To Control Buttons”.
• Press the “+” button and, while holding it, also press and hold the On/Off Mode button for three seconds. LCD will show ― ― .
• Press the On/Off Mode button again to turn system off.
This completes the initialization. The furnace On/Off temperature differential should be set at this time. See “Mode Description - Furnace” on page 9 for further information on furnace mode differential setting”

I will send another update in a week or so. After I’ve done a few drives with the 5th wheel.
Daniellekristopher is offline   Reply With Quote
Old 02-05-2018, 09:25 PM   #19
Senior Member
 
ejohnson1144's Avatar
 
Join Date: Aug 2017
Posts: 421
Yes and even I forgot about that . good job
ejohnson1144 is offline   Reply With Quote
Reply

Tags
furnace

Thread Tools
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

Disclaimer:

This website is not affiliated with or endorsed by Forest River, Inc. or any of its affiliates. This is an independent, unofficial site.



All times are GMT -5. The time now is 02:28 PM.