Purchasing 86 Grand Villa all circuits are on. furnace fan will not turn on. I'm thinking it's something simple.
The blower may be stuck . If the fire lights, the blower should have power . Give it a gentle kick. Is this the unit in Brooksville,FL. Very nice .. About 12 miles from my shop.
NO, if no/inadequate air flow, the SAIL SWITCH will not close so the furnace will not light.
Lighting sequence is:
Fan comes on
Sail switch closes and signals the PC board
PC board THEN opens the gas valve and activates the ignitor.
If you decide to try a new control board, get the one from Dinosaur. They are much superior to the OEM manufacturer board.
Dinosaur Electronics Home. High quality circuit boards for RV appliances. (https://www.dinosaurelectronics.com/)
Ok thanks guys thanks. not in Florida
Make sure there is 12 volts to the thermostat and that the contacts of the thermostat are passing 12 volts to the furnace which has a time delay that will not start the fan for several seconds.
If you are talking about the front furnace the 12V is pigtailed off some other device. I don't recall what it is but once you find another 12V device not working, start there. Could even be a fuse. On my '94 it's the couch lamp but I don't recall on my '87.
Also I've had to turn off and on the thermostat a lot of times (30) before it finally lighted. You can hear the clicks.
On this age coach (or any coach with standard heater) first thing you should look at is to see if you have a good ground. Clean the grounding lug and the metal where it terminates and try again.
Mike
First, Good for you!
The rivets in the mechanical thermostats become corroded with time and will not pass current. Checking for voltage at the wires is a good place to start, and if all is well there and twisting the wires together doesn't bring joy, removing the cover over the fan will allow you to try turning the fan by hand. Dinosaur Electronics also carries a solid state time delay relay.
Just to expand on Brett's time line,
Thermostat closes sending electricity through the time delay relay. After that relay warms up it closes and allows current to flow through the fan motor. Once the fan is up to speed the sail switch closes sending current to the control board. After a suitable electronic delay to allow any built up explosive gases to be purged from the burner, the control board open the gas valve and provides high voltage to the ignition points in the burner. It's pretty easy to follow the power with a volt meter.
When we got our coach the front furnace was intermittent. One time it would work fine - next time it wouldn't. When it didn't work, the fan would come on but the burner would fail to light. When that happened, the fan would continue running constantly (blowing cold air out the heater ducts) until I finally turned the thermostat switch to OFF.
I solved the problem by (first) replacing the rusted-out burner tube, and then (second) replacing the control board with a Dinosaur. Furnace has worked flawlessly ever since.
The Dinosaur board will try 3 times to light the fire before it gives up. This is handy if you have not used the heater for several moths. Seems like the gas can sometimes take a while to get to the furnace burner after a long period of inactivity.
Need Hydro Flame Furnace Burner (https://www.foreforums.com/index.php?topic=23119)
Chuck and Jeannie forget to add that after the Dinosaur board gives up it turns off the fan, waits one hour and tries again. If the batteries are low, that hour's rest may give you enough voltage for one more furnace run. Handy at 3:00 AM when you really don't want to get out of bed to fire up the generator.