Suburban SF-42 furnace still not working!

[ClydesdaleKevin]

Well crap.  I installed the brand new Dinosaur control board in my Suburban SF-42 furnace today...and it still doesn't work.


I tried the same jumper setup I used last winter to test it, and nada.  I'm getting 12 volts to the time delay relay when I turn the thermostat on...but it isn't sending power to the control board.


So I'm going to guess that the relay is bad.  Any thoughts?  The limit switch wouldn't be the problem unless it is running, right?  Same thing with the sail switch...it would have to at least start and then stop for the sail switch to be bad, right?


I'm stumped.


Kev

[Rickf1985]

Have you looked through the furnace troubleshooting on the site here?


http://www.classicwinnebagos.com/forum/index.php/page,page558.html

[ClydesdaleKevin]

Have you looked through the furnace troubleshooting on the site here?


http://www.classicwinnebagos.com/forum/index.php/page,page558.html

Yep.  From the two PDF files I downloaded covering the SF series furnace, my best guess is that it is the time delay relay.

A bad limit switch that is open might also cause the problem, but more than likely it is the time delay relay.

Kev

[DaveVA78Chieftain]

Is the blower motor coming on at all?  Also many of the SF models have a seperate valve switch between the thermostat and the delay relay coil.  Is it ON?
On a SF-42, power goes to valve switch then to thermostat.  Output of thermostat goes to 2 places:
1) Delay relay to turn on blower
2) High Temp Limit switch then to sail switch then to control board so it can turn on gas and light it.

So, if blower is not running, then it is either the thermostat, valve switch, delay relay of blower motor.


If the blower motor is running, then it is the limit switch, sail switch, or control board.

[ClydesdaleKevin]

Is the blower motor coming on at all?  Also many of the SF models have a seperate valve switch between the thermostat and the delay relay coil.  Is it ON?
On a SF-42, power goes to valve switch then to thermostat.  Output of thermostat goes to 2 places:
1) Delay relay to turn on blower
2) High Temp Limit switch then to sail switch then to control board so it can turn on gas and light it.

So, if blower is not running, then it is either the thermostat, valve switch, delay relay of blower motor.


If the blower motor is running, then it is the limit switch, sail switch, or control board.

The blower motor doesn't come at all now, and there is no click from the time delay relay like there used to be.  When I turn on the thermostat in the RV (or rather, have Patti do it so I can listen and observe the furnace outside), 12 volts goes to the time delay relay...but it doesn't even click now, and nothing happens after that.  The motor doesn't start, and no power goes to the control board.

Kev

[DaveVA78Chieftain]

On the delay relay, the red wires are power to the unit and the thermostat.  The blue wire is power to the coil from the thermostat to energize the relay.  When the relay is energized, power to the blower motor is also provided over a 14 gauge red wire from the relay.  So, if there is 12VDC on the red power in wires and the blue wire AND you are sure the blower motor is good, then the relay is defective.

[ClydesdaleKevin]

Thanks Dave.  I'll check power to the blue wire either tomorrow morning, or when I get to my mother's house on Tuesday.


Kev

[ClydesdaleKevin]

On the delay relay, the red wires are power to the unit and the thermostat.  The blue wire is power to the coil from the thermostat to energize the relay.  When the relay is energized, power to the blower motor is also provided over a 14 gauge red wire from the relay.  So, if there is 12VDC on the red power in wires and the blue wire AND you are sure the blower motor is good, then the relay is defective.

Okay Dave.  I tested the red wire going to the relay when the inside thermostat is off, and yes, it gets 12 volts.  I checked the blue wire with the inside thermostat in the off position, and it had no voltage.  So I turned on the thermostat, and the blue wire gets energized with 12 volts...but there is no click at the relay, and then nothing else happens.

So I'm going to safely assume it is a bad time delay relay!  I ordered a new one, and it will be delivered to my mother's house by Friday.

Thanks everyone!

Kev

[ClydesdaleKevin]

Hopefully the new time delay relay comes with instructions, because it sure doesn't look like the old one that is in the furnace right now...lol!


Kev

[DaveVA78Chieftain]

Sounds like a bad relay to me also.  Goodluck

[Rickf1985]

Hopefully the new time delay relay comes with instructions, because it sure doesn't look like the old one that is in the furnace right now...lol!


Kev

Ahh, Just wing it and hope for the best. I hear that is all the Navy electricians did anyway. :)rotflmao

[ClydesdaleKevin]

Ahh, Just wing it and hope for the best. I hear that is all the Navy electricians did anyway. :)rotflmao

LOL!!!

[ClydesdaleKevin]

Well crap.  I installed the new time delay relay (which is HUGE compared to the original...about the size of a pack of cigarettes)...and now I get voltage to the motor when the thermostat is turned on per the wiring diagram, which I didn't have before...and the motor won't start.


Dang it!


So I'm looking at this beast, thinking, "what else could be wrong?"  And I start jiggling wires.  BINGO!!!  On the side of the motor, two wires enter through a rubber grommet, one red (positive) and one black (negative or ground).  If I push IN on the black wire right near the grommet, the motor comes on and starts to spin, albeit too slowly.  So while it is spinning, if I manually close the sail switch, the LED on the new control board comes on, the ignitor fires, and furnace comes on blowing heat!  As soon as I stop pushing on that black wire?  Everything shuts down.


So dang it!!!  Looks like I need a new motor, and the cheapest place I found them is 120 bucks or thereabouts!


Because it will come on if I push in on the ground wire, I'm guessing that it is a bad solder connection.  I looked these motors up, and you CAN take them apart.  So tomorrow morning, I'm going to remove the motor, take it apart, and see if I can resolder the connection...and check the brushes while I am at it.  Worst case scenario, I'll order a new motor tomorrow after my troubleshooting and bench test...but hopefully I can just repair the bad connection and save us 120 bucks.


Kev

[DaveVA78Chieftain]

Whoppie!  Gotta love electronics!  :)rotflmao

Good luck I know just how you feel

[Rickf1985]

Since you already have a diesel you might want to do some research into one of these. I have looked at many reviews and installations and they seem to be a pretty good deal. And you could plumb it into your fuel system and then you aren't sucking your propane dry.


https://www.amazon.com/SUPERFASTRACING-Switch-Diesel-Heater-Motor-Home/dp/B07KMQ3C84/ref=pd_sbs_60_t_1/135-0504114-2676619?_encoding=UTF8&pd_rd_i=B07KMQ3C84&pd_rd_r=20718ce1-66b6-45e9-95cb-f7db60e1588d&pd_rd_w=EZOdu&pd_rd_wg=vg7A1&pf_rd_p=5cfcfe89-300f-47d2-b1ad-a4e27203a02a&pf_rd_r=S07MJ5TMRSP5D8EKY18E&psc=1&refRID=S07MJ5TMRSP5D8EKY18E


Here is another one for a lot more money but appears to be the exact same one.


https://www.amazon.com/Diesel-12volt-Webasto-Airtronic-Eberspacher/dp/B00PDUIH9I

[Rickf1985]

I am actually thinking about one of these for mine since mine tends to use so much propane. This has it's own tank which I could refill from a can without having to try to find a propane filling place.

[ClydesdaleKevin]

I got the old motor out and took it apart...and one of the brush springs was collapsed!  It looks like from extreme heat.  Maybe I accidentally shorted it out when I was testing it?


So down to the Ace hardware store for new springs.  I would have gotten new brushes while I had this thing apart, but Ace and NO other store had them in this small rural town of Fitzgerald, GA.  There is lots of life left in the brushes though, so it wasn't a big deal.


I put the new springs in, reassembled it, and tested it with a 12 volt battery charger...BINGO!!!  Runs like a champ with lots of torque!


Getting the blower housing and motor out was a pain, since there was a cage around the whole thing...so I had my dad cut it off with a cutting wheel and a hacksaw, as I see zero purpose in keeping it there.  You can see what I mean in the attached photo...I had him remove the slotted parts of the top and side sheetmetal that boxed in the blower assembly, etc.


After the cage was removed, putting it all back together was pretty easy.


It is completely ready now to reinstall...but it got dark and started raining, so I'll have to wait until it stops raining (Monday afternoon) to put it back in.


So that should do it!  Instead of paying 120 bucks for a new motor, it cost me .79 cents for two little springs.  SWEET!!!





Kev

[Froggy1936]

Last night Temp 28o My 12 year old Suburban furnace / Hunter Digital Thermostat , Stopped working , Woke up @3:00 AM due to inside temp going down to 65o The electric heater is only able to keep up down to 32o I am running on a spare bottle of propane so first thing Try the stove Burner,ok, Try reprogramming T/S No good ,  Grabbed an extra blanket and went back to sleep .Today Checked wiring diagrams for fuses None. THe only fuse is in the converter, But also feeds Refrigerator and antenna, Both working . Opened up the T/S Found a switch (set from Manufacturer)  Marked Recovery, set to Disable ???Switched to Enable! ALL OK NOW !!  There is NO SUPPORT From Hunter, by phone or on line ! And no Trouble shooting in the Suburban Information ! Frank

[ClydesdaleKevin]

Last night Temp 28o My 12 year old Suburban furnace / Hunter Digital Thermostat , Stopped working , Woke up @3:00 AM due to inside temp going down to 65o The electric heater is only able to keep up down to 32o I am running on a spare bottle of propane so first thing Try the stove Burner,ok, Try reprogramming T/S No good ,  Grabbed an extra blanket and went back to sleep .Today Checked wiring diagrams for fuses None. THe only fuse is in the converter, But also feeds Refrigerator and antenna, Both working . Opened up the T/S Found a switch (set from Manufacturer)  Marked Recovery, set to Disable ???Switched to Enable! ALL OK NOW !!  There is NO SUPPORT From Hunter, by phone or on line ! And no Trouble shooting in the Suburban Information ! Frank

I'm glad you figured it out Frank!  Have a very Merry Christmas...and Louie too!

Kev

[Jamo]

froggy 1936 you said you opened up the "T/S". What is the "T/S"?


John

[Rickf1985]

Thermostat?

[ClydesdaleKevin]

ITS ALIVE!!!  MUHAHAHAHAHAHAHA!!!  :::insert deranged maniacal laughter here:::


We had a break in the weather today, so I reinstalled the furnace, got it all hooked up, and it fired up!!!


And then the flame went out.  I figured it was probably just air in the propane line, so I tried it no fewer than 10 more times.  NADA!!!


Well crap.  Everything that is supposed to happen at the board is happening...green light, red when trying it ignite (and you can hear the click of the sparks), green light...the board tries three times, then eventually the time delay relay shuts it down.


So now I am getting pretty ticked off!  what in the world???


I'm thinking it must be either a bad gas valve and/or igniter element...and start searching Amazon and eBay for them, and the replacement costs.  They ain't cheap, and if I had to buy those too, the money I have spent so far would have pretty much covered buying a brand new furnace!


Then my dad (step dad, but I call him dad) said "hey, why don't you wait a while and try it again...could just be air in the lines."  I politely smiled and nodded, thinking to myself that I already tried 10+ times and that should have purged any air out of the lines, right?...but I didn't say anything since he's 83 and I love the guy.


I bid everyone good night, and came back into the RV, turned on the furnace, and BINGO!!!  Fired right up and stayed lit!


I'm pretty sure it is working now!  I'll try it again in the morning, but as of right now, IT LIVES!!!


Kev

[ClydesdaleKevin]

And...I just turned the furnace on again, and it fired right up!!!  WOOHOOOOOOO!!!


Kev

[DaveVA78Chieftain]

I always lite the stove burners to purge the air from the lines before I try to relight the furnace.

[ClydesdaleKevin]

My little widget came in today, so I tested the amp draw of the new electric heater vs the old ceramic heater.  On low (750 watts) it draws 5.2 amps.  On high (1400 watts) it draws 11 amps.  The old ceramic heater with a fan draws 10.8 amps.


We've been using it on low since I installed it...but it isn't something I'd want to use off of the batteries for very long, even on low.  Perfect for when we are on shore power though.


Kev