Gas Heater Sail Switch

[bruceh]

I have been having an issue with my heater.

When I first start it up, the blower runs for a while and then stops. If I run my generator, it will fire and run.

My batteries are new and fully charged.

Once the furnace has run, it will continue to run and restart. It is just the first time startup after sitting for a while (weeks).

I read the Suburban serice manual that someone posted and it mentions cleaning the 'sail switch'. I would happily clean it if I knew where it was. The manual had no useful pictures of this switch.

Thanks,

[bruceh]

I have been having an issue with my heater.

When I first start it up, the blower runs for a while and then stops. If I run my generator, it will fire and run.

My batteries are new and fully charged.

Once the furnace has run, it will continue to run and restart. It is just the first time startup after sitting for a while (weeks).

I read the Suburban serice manual that someone posted and it mentions cleaning the 'sail switch'. I would happily clean it if I knew where it was. The manual had no useful pictures of this switch.

Thanks,

[JavaJelly]

Had an '04 Discovery w/a furnace that would run intermittently. Paid for a new sail switch. Ended up being a bad board. It was madening as it never seemed to fail w/a service tech or it would fire for a while then lock out and not fire again unless I cut power.

Is it possible that the generator condition is just a coincidence and it really is random and therefore a bad board?

[bruceh]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Is it possible that the generator condition is just a coincidence and it really is random and therefore a bad board? </div></BLOCKQUOTE>

Absolutely! I was going to try to do the easy, cheap thing first and see if the switch is being inhibited by dirt or dust.

[JavaJelly]

I would do the simple thing first too. Please keep us updated on what happens. I did not change the sail switch myself so, I am no help there.

[RV Wizard]

Have you had bug screens over the furnace vents to keep the pests out? If not you may have a nest in the unit that will have to be cleaned out. A restriction of airflow will not allow the sail switch to set. When you have the generator running you are actually increasing the voltage and the motor will run a little faster. This may compensate for a airflow issue. You could have other problems but we ind a lot of debris issue on furnaces.

[bruceh]

The bug screens are an interesting idea and could well help.

My current question is 'how do I get at it to inspect it?' The cold air intake is way to the left in a cabinet and the heater itself is located dead center. I can't see it from the bottom. So, how do I access it?

Should this be in the Winnebago forum? If so, I don't know how to cross post here.

[RV Wizard]

bruceh, I can put in a short cut to the Winnebago forum for you. You will have to remove the furnace. I am not sure what make and model you have, but if there is an outside cover that have four screws you can remove to access the furnace it is not too bad a job. Be sure to disconnect 12 volt power and turn off the gas. check for gas leaks before firing up the furnace when you put it back together. Let me know if I can be of more help and include the make & model #. Thanks

[chasfm11]

Bruce, Mike is far more experienced than I on furnaces and mine is an Atwood, not a Suburban. Here is what I did find on mine.

- the sail switch is actually inside the fan housing. The front part of that housing has 4 screws and can be removed (with some difficulty because of all of wires) by just taking the outside cover off. My sail switch was bad and I replaced it.
- my motor had a bushing, not a bearing on the shaft. In my case, it squealed like a stuck pig on startup. To prove that was my problem, I took enough apart to be able to get to the fan shaft and squirted some oil into the bushing. The squealing stopped and the fan speed was noticeably faster on start up. My oil fix didn't last and I ended up replacing the motor. I'm thinking that if your motor bushing is dry, it could be initially slowing down the fan speed enough not to make the sail switch close. Just a thought.

[DonavonP]

There's a picture of a sail switch on page 7 of this pdf.

http://www.bryantrv.com/docs2/docs/suburbantech.pdf

[bruceh]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by DonavonP:
There's a picture of a sail switch on page 7 of this pdf.

http://www.bryantrv.com/docs2/docs/suburbantech.pdf </div></BLOCKQUOTE>

Now this is a good service manual. From this post and the one prior, I tore into the heater.

Removing the four screws holding on the panel was easy and the sail switch was obvious once I knew what to look for. It was right at the back of the unit (right where the panel came off).

What hit me right away was how filthy everything was. There was dirt everywhere. One close look told me why.

There was a 1/2 gap all the way across the heater. See the picture. My finger is pointing at the gap.


Winnebago had used some self-adhesive weather stripping. The glue strip came loose from the rubber and sagged leaving a big gap to suck in dirt (and cold air). You can inspect from the bottom without removing the panel if you want to check yours.

I glued the weather strip into place and put duct tape across the top. In the spirit of overkill, I also caulked it fom the bottom.

This should keep the dirt out.

Still haven't solved the root problem. I tried turning on all of my 12 volt stuff (lights, inverter, televisions on the inverter) and sure enough, the heater would not fire. This is with new, fully charged batteries. After I turned off most of the stuff, the heater fired and worked just fine.

Back to the drawing board!

Edited to clean up typos and add info about TVs being on the inverter.

[chasfm11]

Bruce, it sure sounds like you have a voltage problem. While I don't understand your comment about televisions in the 12 volt circuit, my suggestion is that you do all of that again and then put an accurate digital volt meter on the 12 volt entrance point to the furnace. Just because the batteries are putting out good voltage, doesn't mean that the furnace is seeing that. A high resistance connection somewhere could be dropping that voltage.

[TandW]

We had intermittent problems with our heater for years that were described as sail switch problems and servicing the switch was to no avail. The solution was to add a noise suppression filter to the furnace power lead at the appropriate fuse. No more problems!!

[bruceh]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by chasfm11:
Bruce, it sure sounds like you have a voltage problem. While I don't understand your comment about televisions in the 12 volt circuit, my suggestion is that you do all of that again and then put an accurate digital volt meter on the 12 volt entrance point to the furnace. Just because the batteries are putting out good voltage, doesn't mean that the furnace is seeing that. A high resistance connection somewhere could be dropping that voltage. </div></BLOCKQUOTE>

I turned on the televisions to put more load on the inverter.

I think that you hit it. I went at this with three DVMs. Winnebago installed one at the control center and this one senses what the coach sees, I installed a Siemens solar controller with built in DVM and I put a Sears DVM right on the battery.

With everything static (nothing turned on), they all reported very similar voltage. As I turned things on, the coach DVM fell as low as 11.2 while the battery showed 12.5.

Examining connections, I see a rusty looking grounding block. I will clean that up and keep checking.

I mostly came inside to look at the Winnebago wiring diagrams to see if I could figure another likely suspect.