Heater works fine with the top cover removed ,shuts off in 5 sseconds when cover is replaced. Fan is not hitting the cover

CHANGING THE DRIVE BELT
1. Remove the top cover and the rear panel.
2. T720/780: Remove the external fan housing.
3. Remove the special tool.
4. Remove the belt from the belt pulley and take off the belt.
5. Feed the belt over the drum onto the motor shaft and over the belt pulley.
6. Install the special tool.
7. T720/780: Replace the external fan housing.
8. Replace the rear panel and top cover.
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REMOVING THE TOP COVER
1. Remove the three T20 screws at the rear of the top cover. (Keep the two star washers.)
2. Tilt the cover and pull it backwards.

REMOVING THE REAR PANEL
1. Remove the top cover.
2. Unscrew the centering nut until the face of the nut is level with the end of the thread and knock out the bearing.
3. Fit the special tool (part no. 88 011 54) by fitting the tube end into one of the stamped out keyholes in the front rail. Lift the rear edge of the drum and press the drum edge onto the roller.
4. Remove the ground connection (yellow/green wire) from the input terminal block (see pages 8 and 9).
5. Take the cable bundle out of the cable clamp and pull the header block off its terminal pins.
6. Remove the wiring:
T700/T720: R1 a, R1 b, R1 13, R1 14, R1 34 on the contactor.
T760/T780: Ra, Rb, R13, R14, R34 on the contactor and F3 and F4 on the radio interference filter.
7. T720/T780: Remove the hoses to the water tank housing.
8. Remove the centering nut and the eight screws.
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NOTE: Do not remove or loosen the screws around the heater housing or drum bearing.
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9. T720/T780: Remove the three plastic screws at the lower part of the rear panel.
10. Lift off the rear panel.

REMOVING THE EXTERNAL REAR FAN HOUSING
1. Remove the top cover and rear panel.
2. Unclip the external rear fan housing suction side.
3. Unscrew the 10 mm nut on the external rear fan wheel and remove it.
4. Lift the external rear fan housing motor side and pull it toward you.

Dado

First, remove the top cover. Inspect for a varmint nest. If clear, manually spin the fan. If it does not you either have a broken rotor that is binding or you have a bad bearing.

If it spins freely, apply power- see if the motor runs with the top cover removed.
If YES, replace the top cover. Its possible that the top is binding the fan.
If NO, the start capacitor is defective. The cap on R115 is internal and is not servicable.

Reading material about a hummer

If the fan is spinning quite fast then the overheating problem is most likely dust clogging the fan and heat-sink assembly. Blasting air into the fan and heat-sink can only make it worst as you are forcing the dust further into the heat-sink fins.
Remove the panels covering the vent and fan/heat-sink, loosen the dust and vacuum to remove this dust off the fan and heat-sink. Check the fan to see if it spins freely, if not replace the fan.
After re-assembling and boot up, if you still have heating problems, addition cooling can be employed by purchasing a laptop fan assisted cooling pad. Place the laptop on top of this pad and the fans on the pad will direct additional cooling air to the laptop's vents.

Have the front heater core flushed ,since there is heat to the rear the thermostat is fine so it could be plugged.If the fan works on no speeds the check the fuse for the heater fan,if it's good you neerd a blower motor.

When the cover is off it totally changes the airflow through the burner chamber. There is no thermal overload on this heater. The flame sensor not sensing flame is what causes the heater to shut off. Make sure the fuel filter is clean. It is located under the grommet where the fuel line enters the tank. Remove the nozzle and clean it by blowing backwards through it with compressed air. If the heater is very old the nozzle should be replaced. Set the air pressure to between 4 and 5 psi. This should cur your problem. Let me know if you have any questions.

Thed fan should come on soon after plugging in as long as the heater is cold. The heater then shuts off after sensing no flame. Either the wiring is bad, the fan motor is bad, of the top has been bent down so it is hitting the fan. Remove the top, make sure the fan turns freely and check power to the fan motor. The fan motor also turns the air pump that **** the ful out of the tank. Ck this and let me know if you need help.

If it were mine- and the heater has been inactive for several years, I'd check for a rat's nest inside. If clear, it's time for some serious troubleshooting. Remove the top cover. Is the fan turning?

i have to start my heater manually. whats bi start it the controller works its when the heater hits its tempature it will turn off thats good, but when i re-start it with the control it wont start. i have to do it manually remove the cover on the heater and push a buttom on top. the pilot is always on?

The air intake vents in the rear were clogged with dust. They needed to be brushed and vaccumed.

Found the fault. It's the heat ring in the main oven. MAKE SURE THE MAINS POWER IS OFF PRIOR TO COMMENCING THIS WORK!!!!! 1.Simply remove the four screws that fix the fan surround in the main oven. 2.Remove the rear cover fixing screws and remove the rear cover. ( the cable passes through this so just rest it to one side ). 3.Remove the two push on spade connectors from the heater element ( positioned just down and to the right of the fan assembly ). 4.Remove the four heater element fixing screws from inside the main oven. 5. The tricky bit. . . There is one more fixing at the top of the fan in the main oven. I could not get the fan off its spindle, but the next step sorted this out. 6.Remove the three fan fixings from the rear of the oven. This allows the fan to wobble/move enough in the oven to remove the final heater fixing screw at the top of the fan. 7.Pull the heater element into the main oven. No doubt it has a very grey and flakey appearance to part of it! 8.Buy a new one and replace it in reverse order, remembering to replace all fixing screws as you go. 9. If you forget which way the cables on the heater element go, the one with the red marks on it goes to the left as you look at the back of the oven from the outside. ( nearest the fan assembly ) I know this all looks a bit long winded, but it really is quite simple if you follow the notes above! Hope this helps someone. Might just save a ridiculous call out charge from the professionals!!!! Best of luck, Keith.