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Old 12-12-2019, 08:28 PM   #1
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RV Furnace won't turn on.

Furnace stopped turning on a couple of days ago. I've remove the furnace and checked all the connections. Since it was out I did a tune up on the unit changing out the filter and burner and igniter and board. When I turn on the heat from my thermostat I can hear a click from the ac unit. When I switch to ac and turn down the temp the ac still works. Can something in the ac control board keep the furnace from turning on? My furnace is a Suburban SF-42F and my ac is a dometic duo-therm. My thermostat is analog. I have a 2007 Forest River Cardinal.
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Old 12-13-2019, 01:26 AM   #2
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My furnace kicks on and blows weak cool air then shuts off after about 5 min ,sometimes air is warm
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Old 12-13-2019, 06:37 AM   #3
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Took it out and did a tune up ? yeah....right. BTW...they don't have filters.

Is this National Troll Week ??
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Old 12-13-2019, 02:49 PM   #4
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Took it out and did a tune up ? yeah....right. BTW...they don't have filters.

Is this National Troll Week ??
My bad should have called it by it’s name burner access door gasket. Anyone with a little bit of mechanical know how can learn and read schematics to take something apart and put it back together. Electrical is where I take longer and ask more questions. So if you have nothing of note or anything pertaining to my issue please refrain from upping your own post count with flippant remarks.
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Old 12-13-2019, 02:58 PM   #5
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If you disconnected the propane line, it will only try to ignite a few times before it times out. Sometimes this isn't enough to get all the air purged. You have to turn the thermostat to "off" and then back on to heat, or furnace, and let it start the sequence again. Sometimes it takes several tries to get all the air purged from the line.
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Old 12-13-2019, 03:24 PM   #6
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If you disconnected the propane line, it will only try to ignite a few times before it times out. Sometimes this isn't enough to get all the air purged. You have to turn the thermostat to "off" and then back on to heat, or furnace, and let it start the sequence again. Sometimes it takes several tries to get all the air purged from the line.
I know air needs to be purged from the lines. The blower doesnít even start. When I switch the thermostat to heat I can hear a click from the ac in its control box. So my question is can something in the ac being faulty cause the furnace from getting the signal to switch on.
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Old 12-13-2019, 03:37 PM   #7
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I know air needs to be purged from the lines. The blower doesn’t even start. When I switch the thermostat to heat I can hear a click from the ac in its control box. So my question is can something in the ac being faulty cause the furnace from getting the signal to switch on.
Yes.
There is a relay board located inside the A/C ceiling panel on certain Dometic units.
It connects to the Comfort Control center via a phone/data cable.
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Old 12-13-2019, 04:10 PM   #8
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My bad should have called it by itís name burner access door gasket. Anyone with a little bit of mechanical know how can learn and read schematics to take something apart and put it back together. Electrical is where I take longer and ask more questions. So if you have nothing of note or anything pertaining to my issue please refrain from upping your own post count with flippant remarks.
Take the two blue wires going into furnace and jump them together . these are the t-stat wires if it fires up then the problem is before the furnace . most likely a t-stat issue
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Old 12-14-2019, 06:38 PM   #9
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Did you check the sail switch. That is the small in-line airflow-activated switch that tells the computer that there is airflow (from the fan). This then allows the computer to open the propane valve and energize the ignitor. I've had two sail switches replaced this year. Thankfully both times under warranty.
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Old 12-17-2019, 11:21 AM   #10
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As Mr. M. said, short the thermostat wires to the furnace together and see if it'll run. If it does, the issue is not with the furnace. It's likely in the A/C control box, possibly a loose connection.
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Old 12-18-2019, 01:38 PM   #11
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Take the two blue wires going into furnace and jump them together . these are the t-stat wires if it fires up then the problem is before the furnace . most likely a t-stat issue
furnace motor runs when i jump the wires, I jumped the furnace wire in the t-stat to the ground wire and i get the same click from inside the a/c unit where the relay control board is. my guess is faulty relay. I haven't dug too deep into the configuration of the board but are the relays like in a car plug and play or are they soldered in?
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Old 12-18-2019, 02:19 PM   #12
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As I said earlier, check the sail switch (just push on it) with the power on and before the ignition sequence times out, i.e. less than one minute. My FR dealer service chief told me there is a known high failure rate on sail switches. I've had two failures within one year with both under the two year manufacturer's warrantee.
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Old 12-18-2019, 02:42 PM   #13
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As I said earlier, check the sail switch (just push on it) with the power on and before the ignition sequence times out, i.e. less than one minute. My FR dealer service chief told me there is a known high failure rate on sail switches. I've had two failures within one year with both under the two year manufacturer's warrantee.
Sail switch doesn't come into play until the blower starts . OP blower doesn't start when tstat calls for heat
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Old 12-18-2019, 02:43 PM   #14
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furnace motor runs when i jump the wires, I jumped the furnace wire in the t-stat to the ground wire and i get the same click from inside the a/c unit where the relay control board is. my guess is faulty relay. I haven't dug too deep into the configuration of the board but are the relays like in a car plug and play or are they soldered in?
Not sure the brand of AC but you should be able to order from amazon anything needed
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Old 12-18-2019, 03:17 PM   #15
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https://youtu.be/yjTbZEs5VwI Hope this helps
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Old 12-18-2019, 05:08 PM   #16
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When I have problems with the furnace the first thing I check is the propane, I light the stove to make sure I have propane. I let the stove run plus I turn the gas hot water heater on, you may have to run water until the gas burner comes on. If the furnace still doesnít work I check the battery, I disconnect from the power supply. The furnace actually gets it power from the battery. If the furnace still doesnít work I call the RV repair man
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