I found a service manual today that covers your furnace. Page 24 (Sequence of Operation for Fan Control Module Board) explains how yours functions. Page 28 has a troubleshooting guide for that style.
Your hi limit switch may be cycleing due to the restriction of air. One thing that the manuals do not mention is that the board will allow the hi limit to cycle (overheat) 6 times and then it will shut down the heater for one hour. Then it will restart the cycle. If you disconnect all power to the heater (pull fuse) and reconnect the board will start over again without the one hour delay. If limit switch cycles address the over heat problem. Airflow or to much fire?
1994 27sl Alpenlite, 2001 Dodge Cummins auto 3.54 stock
enblethen wrote: Once the fan starts it should take 10-15 seconds for time delay relay to send 12 volts DC through the sail switch and thermal fuse to circuit board which then lights the furnace.
It could be dirty sail switch. A small piece of debris could be restricting it's operation.
The connector on the circuit board could be corroded. try cleaning it with a pencil eraser, white is preferred.
It could be the thermal cut out but I doubt it
X2... mine was a flakey sail switch. Sometimes it just blows cold air for a short time, then shuts off. Next time it starts right up.
1998 Triple E F53 with 460 Ford
1995 Jeep Wrangler toad
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