Heater Re-ignition Problem
 

Heater wouldn't work in 1988 Fun Maker w/Suburban furnace so I removed the unit, opened it up, and cleaned out a dirt dobber nest. Now it works, somewhat... when I switch the thermostat on, I get blower, then igniter, flame, and presto, heat! When the temp reaches the thermostat high limit, I get flame-out, then blower continues to run 52 seconds before shut-down. So far, so good.

The next time (after the temp falls below the thermostat low limit,) I get blower, igniter, no flame, and cold air for about 30 seconds before shut-down. This process repeats until I manually switch the thermostat off, then back on, then magically it'll work just fine again for the first cycle, and fail again on the next one.

Any suggestions?

Go to this page and pull up the service manual pdf file. On the eight page it explains the operation of the unit and then goes on to diagnosis. It may help you. It may not be the model of your furnace but may be generic enough to give a general idea of what is happening.

https://www.hilotrailerforum.com/f65/...al-nt-12s-100/

Check the gas pressure with a gas pressure gauge, I had to replace my propane regulator. My furnace was doing the same thing.

Thanks for your suggestions and the pointer to the service manual. I had already isolated and excluded gas pressure as the problem. By turning off all lights and disconnecting the fridge, the re-ignition problem seems to occur less frequently and will usually work on one of the retrys before lockout occurs. (Low voltage???) I'm going to pull the burner out again to make sure it is thoroughly clean and free of all the dirt dobber debris, and check the gap on the igniter.

Does anyone know how to get to the sail switch to make sure it is clean and working correctly?

Try cleaning and tightening all the electrical disconnects to and on your furnace, including both slip on connecters and screw downs. Also check the ground connection. Whenever I start having operational issues with older appliances, and other electrical stuff, it seems like half the time just cleaning and tightening up the connections fixes the problem.

On some of the more exposed electrical connections, on our trailer, I apply some dielectric grease to the disconnects to help prevent corrosion and promote conductivity. Just don't use it anywhere near a circuit board!

Jim

Read all the messages re: Heater issues and have 1 question
 

Tried just about everything recommended regarding getting the heater started. Just one question: is the blower supposed to come on first , before anything else? We do not hear any clicking sounds, no gas smell, checked the fuses, have 12 volts, have a ground, replaced the thermostat (we had a hi lo years ago and saved all of the parts from it !) Trying to remember all the things we used to do! Just had this 1987 Voyager towed to NJ from NE - great condition, but this furnace will not come on. Did not change the gas regulator yet...any advice is welcome. Chris and Deb

Even something as simple as a spider web in the gas supply tube will hopelessly interfere with proper ignition or burning. I don't know what the answer to this problem is, but I'd love to find one that will keep my patio heater from being invaded by the little critters.

And, I cannot recall for sure if the blower comes on first or not. I think it does, and I know it stays on afterwards to extract the last bit of heat.

- Jack

Yes, on mine the blower comes on first before the burner tries to ignite. When the blower comes on it closes a sail switch to supply power to the ignition control. You will hear the clicking sound then. Mine has a on/off switch on the thermostat that is very hard to move to the on position and a on/off switch on the furnace also. Sounds like you do not have power to the blower. Check for power to the thermostat and thru it to the ignition control. No need to change the regulator or gas valve if the blower is not coming on and you do not hear the igniter clicking. Good luck

This is "off topic" a bit, but I took my thermostat apart and did a little "surgery" on the lever catch. I think I just filed it off a bit. The result is a lever that doesn't feel like you're going to break it when you move it and it doesn't cut into your fingers anymore when you push on it either.

I don't have any pictures, but the "modification" is very obvious once you open the thermostat. (I actually had one at Camping World opened there when I was thinking mine was defective and was going to replace it. I found the new one was just as bad as mine.)

- Jack

Thanks for the suggestions!
 

Will be working on it again today!

Jack,

Thanks for the suggestion regarding the thermostat on/off lever. If the OEM intentionally designed this lever to be so hard to switch, I wish they had included a persuader hammer... That thing is a real nail buster! :mad:

I'll be modifying ours when we pull the trailer out of storage this coming Monday. Also looking forward to trying out our new tire pressure monitoring system! :)

Jim

Like I said, I was ready to replace the whole thing until I found the replacement was just as bad. In my case, I was really concerned I was going to break the lever, since it's made out of plastic.

- Jack

I moded our 95 and it wasn't to bad. This winter in our 2209 I woke up early and was cold went to turn on the heat, had to used a knife handle before because it was so hard to move, well being still half asleep I pushed the wrong way and broke the lever off.
You just reminded me that it needs fixed.

I have been thinking about getting an electronic thermostat as a replacement for the world's cheapest thermostat that we all have. A heat only non-programmable thermostat is what is needed. The Hunter non-programmable thermostat sold at Wally World seems to be the most popular one that is used. I will try to track down the online article that give all the nitty gritty details. The electronic thermostat provides much more even heat control.

If you want to keep your present thermostat and make it work better without the wide temperature swings, adjust the heat anticipator which is located on the back plate. It is a little lever that can be moved to adjust the on/off cycle. I moved ours to about mid scale and it improved the operation of the furnace. The furnace now runs more often but the temperature variation is much less.

Electronic thermostat
 

I would like to know more about the conversion to the electronic thermostat. It sounds like a good idea, and I would like to try it. But I wonder if it is just a swap, or is there more to it?

You will need a thermostat that uses batteries to power the thermostat circuit, that is why the Hunter thermostats work best. The others are made to be powered by the 24 volt thermostat circuit of a house installation. You will need to add a switch to turn on and off the 12 volt line from the furnace to disable it when not in use, like the on and off lever on the stock thermostat. If I can find a simple conversion posted online I will add it. The articles that I have found so far are mainly for motor homes that have A/C also controlled by the same thermostat. It's a bit more complicated.

Here is one of the articles: RV Digital Thermostat Upgrade | ModMyRV

Thermostat
 

In the past I have my husband read the posts about changing the original thermostat to the Hunter model at Walmart. We replaced ours with the original model. I agree it will break your finger or make you say some unkind words. He wonders about the road vibrations/harsh ride on the Hunter model. Will it hold up.? We replaced our thermostat because it was shot.

Electronic Thermostat
 

We installed an electronic non-programable digital thermostat on our 97 21ft Towlite. We installed is a Robert Shaw model #9405 heat-only battery powered thermostat that we purchased from grainger.com

We removed the existing thermostat. reused the 2 control wiring (one red & one white) that was already in the hi-lo. The new thermostat had indicators for the red and white wires. It was "plug n play". No rewiring necessary.

We have not had any trouble with the vibrations from towing the trailer.

Does that thermostat have an on/off switch to positively turn off the furnace when not needed and to prevent turn on when the the trailer is in the down position?

The Hunter thermostat model # is 42995B. It uses the same two wires that the factory installed White-Rogers thermostat uses. The mounting plate holes are not the same. However, the Hunter mounting plate does cover the original mounting holes. The unit does have a Heat/Off/Cool switch. It uses 2AA batteries. It also has "raise & lower" temperature keys. The Hunter is a nice looking unit and has performed well for me. It is an easy install.

Bob