Gas furnace won't turn on :(

the bear II wrote:

Thermo coupler may have failed....this is common. Here's some info http://www.rvforum.net/SMF_forum/index.php?topic=22178.0

Does a unit without a pilot light still have a thermocouple ??

More likely that the electronic ignitor has failed.

BUT....the recent replacement of the control board is a bit suspicioius.

Professional assistance might be required.

It will not hurt to try a correct size fuse if you aren't sure the current fuse is bad. If you do have a blown fuse you would stand the chance of blowing another. To prevent that you can try the furnace fuse in another slot that you know is working. That way you don't blow another.

All situations are different, but a bit of water in the floor under the furnace doesn't usually cause a problem. But it does sound like you have a bit of a leak in that area you'll need to seal up.

Read the link Old Biscuit sent, there may be something in there about that particular model that will help find the issue.

Do not switch fuses around unless you are certain the fuse is rated the same as the fuse your wanting to swap out...good luck

Oh...and another thing that might be important to mention....we washed the motorhome for the first time a few days ago because it had gotten so filthy with salt and road grit. Well, when we did open the furnace compartment today to have a look, the floor of the compartment was wet, so we must have gotten water in there when we washed (we didn't really think about the fact that there could be areas we would need to be careful when rinsing with the hose). Could that have caused a problem?

Old-Biscuit wrote:
DC fuse supplies power to fan motor....fan motor has run first before anything else can happen.

Looking at a fuse does not prove that 12V DC is available....need to test that you have 12V DC to and THRU fuse (fuse could be good but have bad contacts etc.)

Click at t-stat is contacts making up......DC is then sent to a timed delay relay where DC power is then allowed to go to fan motor.
Bad Fuse, bad timed delay relay, bad motor

You didn't state which brand/model of furnace so here is a 'generic' guide (all rv furnaces basically work same/same components etc)

***Link Removed***

This is good info, thank you! So, maybe it is the fuse, but I'm not really sure how to check it right now, as I am stuck in the RV while my hubby has he car at work today. I don't have any spare fuses. Would it be bad for me to remove a fuse from another spot and just try it in the furnace spot to see if that fixes things, or would that not be wise? Please don't flame me if this is a big Nono, like I said I am new at this and electrical stuff is something I don't know a whole lot about, but I am very good at learning if I can just come across some helpful people. Please be helpful to me and not condescending...not saying that anyone has been, I just know how people can be on forums.

For whoever asked...yes the propane is on. The rear furnace is working just perfectly and he front was working as of yesterday.

He furnace is an Excalibur 8500-III series propane furnace, if that makes anything more helpful. Oh, and the previous owner installed a dinosaur furnace control board on it just a few months ago.

If you have the small, 2.5 square thermostat, remove cover, locate the two wires going to furnace. Connect them together the furnace fan should start and then produce heat shortly. If this happens you have a bad thermostat.

DC fuse supplies power to fan motor....fan motor has run first before anything else can happen.

Looking at a fuse does not prove that 12V DC is available....need to test that you have 12V DC to and THRU fuse (fuse could be good but have bad contacts etc.)

Click at t-stat is contacts making up......DC is then sent to a timed delay relay where DC power is then allowed to go to fan motor.
Bad Fuse, bad timed delay relay, bad motor

You didn't state which brand/model of furnace so here is a 'generic' guide (all rv furnaces basically work same/same components etc)

RV Furnace Troubleshooting

Is the propane on ?

Thermo coupler may have failed....this is common. Here's some info http://www.rvforum.net/SMF_forum/index.php?topic=22178.0

All wiring connections tight and clean