Furnace Troubleshoot

[patrick51]

First problem w/ the 07 Suburban furnace. No pre-igition blower startup, I have 12v. to the unit. Not sure if I need to start w/ the thermostat, or pull the cover off of the furnace and look internally. any suggestions appreciated.

[Ford_6L_E350]

First, are you saying that ignition happens even though the blower doesn't come on? Or that the blower doesn't come on, so ignition doesn't happen.

The blower should come on first, the air movement causes the sail switch to close and then ignition can happen.

If the first case, you happen multiple problems, the ignition while the blower is not working and the fact the blower isn't going. In this case, the thermostat is triggering the ignition, but not properly.

If the 2nd case, it could be the thermostat, power to the furnace or power to the blower motor. A Volt-Ohm meter would be handy to isolate the problem.

Mike

[Scalf77]

Here is the service manual if that helps. As Mike said need a little more detail on failure mode.

-greg

[patrick51]

I have 12v power to the furnace, but the blower is not starting thus no activation of the gas valve or ignition.
Today I removed the thermostat and had it checked, it is OK. Then I bypassed the thermostat, just to be sure and still power to the furnace but no blower. then I removed the bed support vertical board to get access to the furnace panel. with a long rod I moved the vane and still no actiavtaion of the blower, and the fan blades moved easily with use of the rod. I decided it is either the blower fan motor, or the circuit board in the furnace so removed the entire unit. I now have it at a RV shop and they are troubleshooting the furnace. This may help others if someone else has problems. first the thermostat check, then check the vane and blower movement. I will send a follow-up of my findings.

[patrick51]

Follow-Up Furnace trouble. This refers to a RB-50 Ford with the Suburban furnace mounted in the rear, below the sleeping bed. Unseen before is an inset ON/OFF switch where the wiring harness enters the furnace enclosure,facing the rear of the van. This cannot be seen unless looking directly into the opening and impossibe with the rear bed support board in place.

Apparently the wiring harness was moved by something when offroad and it shut the manual switch to the off position. A simple fix if one knows about the inset switch.

[jage]

Originally Posted by patrick51

Unseen before is an inset ON/OFF switch where the wiring harness enters the furnace enclosure,facing the rear of the van.

What year?

[patrick51]

The referenced discussion for thr hidden gas manual switch is on a 1997
ford RB50 layout, where the wire loom enters the metal furnace enclosure.









ford