Suburban Furnace (Dynatrail NT30, 1985 model) Won't Start

[William Briggs]

Last week, I thought I'd test the furnace before wintertime. I flipped on the wall thermostat, turned the temp lever up. After a few seconds, I heard a click in the furnace, then nothing more happened. Tried several times, same thing.

 

Researched the problem on the internet. Learned that the most likely culprit was a bad "time-delay relay." Following the instructions on the internet, I slid the furnace out, jumped across the relay, and the furnace worked. So I ordered a new relay online. Should have been easy enough. The new relay arrived yesterday, so this morning I pulled out the furnace, replaced the relay. But the furnace is still doing the same thing ... turn on the thermostat, wait a few seconds, hear the click, but nothing more.

 

As I understand it, the thermostat needs heat, so it sends current to the furnace relay. The relay (time-delay) then turns on the fan after 25 seconds. Once the fan turns on, it trips a "sail switch" and the furnace fires up. But I can't get the fan to come on without jumping a wire across the relay.

 

Has anyone experienced this problem? I'll be carrying the furnace to the RV repair shop next week, unless someone has an idea.

 

Best regards,

 

Billy

[William Briggs]

I guess I should have calmed down and spent more time with it. I agree John T knows what he's talking about. But for a non-technical person (I'm an accountant), the whole problem was terribly frustrating. Took it to the shop instead. After it spending a month in the shop, and paying $400 to get it out of the shop, it does work well now ... they got the problem fixed. But I sure don't like dropping $400 to solve a problem I might could have solved myself with a $15 relay.

[William Briggs]

P.S. Honestly, the furnace has been tempermental since I bought the rig a year ago. If that $400 has genuinely solved the problem, then maybe it was worth it.

[Mr.&Mrs.vonRabenau]

Sorta anti climatic Bill, like, what was the problem?

 

[William Briggs]

Tech said the fan motor was "seizing." Now, when John T and I were looking at it, the fan motor was not the issue; we had isolated the problem to the "time-delay relay" which I ordered & replaced. But then, I couldn't seem to get the fan to run; so I suppose it was "seizing" at that time. I don't know anything; I would not have thought a "seizing" problem could be intermittent. But since I've had the rig (one year), the furnace has occasionally stopped working but after a few hours seems to start again. So, the tech was certain that one problem was the motor intermittently "seizing." (Is that possible?)

He also said he replaced the sail switch, which he said was broken, but I understand the furnace would have never fired up had the sail switch been broken. I figure it may have been loose or cracked or something.

 

 

[William Briggs]

He said he had a lot of difficulty finding a replacement motor; the one called for is not available but he found another which would work. And the screws to the housing were all rusted, so he had to drill them out. Then, replace a gasket sealing the housing for the blower.

So, the furnace has a new "time-delay relay," a new fan motor, a new sail-switch. Honestly, it fired right up (after bleeding the air from the propane line). And has been cycling on and off just fine since then.

[Dick Monehue]

Never had no problems out of mine, but its an atwood furnance. You might try www.camperpartsworld.com They sell suburban water heaters and parts I believe.

They got a bunch of rv parts to choose from too. I love them and I've been camping for almost 40 years.

[redwing]

what you need to do is see if the time delay is getting the proper voltage and ground on either side and getting voltage from the thermostat. one side of the time delay goes to ground the other side goes to the limit switch, and the third goes to the thermostat.

 

the wire from the thermostat is red, the wire from the limit switch is brown, and the ground is green. the thermostat wire should have 12 volts when the thermostat is turned on, which in turn makes the coil inside the time relay come on after 10-30seconds it closes and provides 12 volts to the limit switch which also then provides 12 volts to the board and then onward to the gas valve and igniter.

 

check thermostat for 12 volts, check ground on time delay, check for voltage out of time delay on brown wire after 10-30 seconds, it should then be 12 volts. if ok then on to sail switch, check sail switch for voltage after fan has reached 75% rpm. if no voltage either the time delay is bad or fan motor is not getting up to 75% or sail switch is bad.

 

i'll leave you with the manual for that furnace which has troubleshooting in it.

 

http://manuals.adventurerv.net/Suburban_Dynatrail_NT-_Series_Furnac...

 

ps: just threw one away as the fan motor died and was cheaper to buy a new furnace than to play with the old one.