Model r115dt, runs for about 5 seconds then turns off. Fan turns, and i see a red glow, but nothing.

bearings in the motor are tight, try oiling the bearings and let me know,

Could be a dirty air filter. Fuel nozzle could be clogged. Fuel filter clogged, if it has one. Some don't. Could be a problem with the low pressure compressor that is attached to back of the fan motor.

I would suggest you change the flame sensor. It will be a small diameter probe extending into burner compartment,usually over or inbetween burners. If your furnace is lighting the burners but they won't stay lit That Is what I would do first.. I also would turn thermostat to fan on to make sure you don't have a problem with the fan. Hope this helps you. Thanks

The ignitor only glows for 5 seconds, then quits. During this period the flame should have lit and will perpetuate itself. If there is no flame, then you have problems and you must start by setting the air pump pressure, which is easier than it sounds. Read these troubleshooting tips.

Check the air filter the fuel level, fuel filter and the fan tightness, this should rotate smoothly.

Neither of you state the model of heater that is giving you starting problems. many of the motors have an external starting capacitor (relay). If so, you may just need that part, if your heater is equipped with one. On the other hand, many have an internal capacitor , which is not servicable.

Dustin, The ignitor only glows for 5 seconds, just long enough to ignite the fuel. The heater is shutting down because the photocell does not see the correct flame color.
Since you say "comes on for 5 seconds", I can only assume that there is a flame. You do not specify a lack of flame. I am also assuming that you have had the heater running this heater season and the problem just started.

YOU must find out if the problem is fuel delivery related or electronics related. Start by checking the pump pressure.

Follow these troubleshooting tips

element should glow dull red when on fan oven but not bright red. are you sure fan is operating? remember there are two fans - oven fan and casing fan and you may be listening to casing fan

runs for awhile shuts down with a big puff of smoke comes out poured diesel 911 thought i had water in diesel fuel cans nothing help need solution ASAP

If I was abetting man - I would suspect that the fan is polarised, and has been wired incorrectly..

Check that there is nothing obvious in the way of the fan blades..