The cooling fans start up at random times, they also turn off immediately the grill is turned off.

either a bad connection on the element terminals or faulty element

Its a good chance its the thermal control board to the fan (PCB),if faulty it doesnt allow fan to reach correct speed thus overheating.
Hope this helps

It could be the thermal cutouts operating. First things first, is the cooling fan running and does it turn off about 10 mins after the ovens/grill are turned off? If it isn't running then the unit is overheating and the thermal cutouts will operate. If it is running normally, then the cutout could be switching in early due to them becoming old and ineffective. There are two cutouts in the oven. One controls the main oven and the other controls the top oven. However, the grill operates without the clock being set, i.e. it is independent of the clock. So, if both the top oven and grill stop working together, according to the wiring diagrams in the handbook, the only thing it could be is the thermal cutout for the top unit.
F.Y.I. The top oven switch controls both the grill and the oven elements. In other words, in its OFF position, the Grill works and the Oven doesn't and in its ON setting the Oven works and the Grill doesn't. However, I can't see this failing as you specify, but worth checking if you take the oven to bits. The Grill will only work if the oven door is down.
If you need to replace the cooling fan, you will have to take the whole unit out of the kitchen cupboard to gain access to the top and rear oven panels, which have to be removed to gain access to the cooling fan and wiring. If you do replace it, ensure all the vents for air circulation are free from dirt and grease before you put it all back.
Try espares for STOVES spares. If the item is not listed you can ask them for a quote.
Be aware that the cooling fan is controlled by a timer circuit board and an in-line resistor on the fan terminal block. Either or both of these two and or the fan could have failed if the fan is not running! Any competent electrician should be able to work out what has failed.
All the diagrams are in the Handbook. If you need a copy, supply an email address and I will send you a pdf copy.
If you do ask for a quote, I suggest you ask for prices for all the parts mentioned above, so once you have checked what has failed, you will have enough info on pricing and availability as to whether to proceed or not.

It could be the thermal cutouts operating. First things first, is the cooling fan running and does it turn off about 10 mins after the ovens/grill are turned off? If it isn't running then the unit is overheating and the thermal cutouts will operate. If it is running normally, then the cutout could be switching in early due to them becoming old and ineffective. There are two cutouts in the oven. One controls the main oven and the other controls the top oven. However, the grill operates without the clock being set, i.e. it is independent of the clock. So, if both the top oven and grill stop working together, according to the wiring diagrams in the handbook, the only thing it could be is the thermal cutout for the top unit.
F.Y.I. The top oven switch controls both the grill and the oven elements. In other words, in its OFF position, the Grill works and the Oven doesn't and in its ON setting the Oven works and the Grill doesn't. However, I can't see this failing as you specify, but worth checking if you take the oven to bits. The Grill will only work if the oven door is down.
If you need to replace the cooling fan, you will have to take the whole unit out of the kitchen cupboard to gain access to the top and rear oven panels, which have to be removed to gain access to the cooling fan and wiring. If you do replace it, ensure all the vents for air circulation are free from dirt and grease before you put it all back.
Try espares for STOVES spares. If the item is not listed you can ask them for a quote.
Be aware that the cooling fan is controlled by a timer circuit board and an in-line resistor on the fan terminal block. Either or both of these two and or the fan could have failed if the fan is not running! Any competent electrician should be able to work out what has failed.
All the diagrams are in the Handbook. If you need a copy, supply an email address and I will send you a pdf copy.
If you do ask for a quote, I suggest you ask for prices for all the parts mentioned above, so once you have checked what has failed, you will have enough info on pricing and availability as to whether to proceed or not.

First things first. The oven element is totally separate to the grill element. The clock has to have a time set for either the top or bottom oven to work, whereas the grill will work without the clock being set.
The control knob for the top oven is the ONLY control that will turn the top oven lights on, the grill does not turn the lights on. ( If you want to watch your toast, you have to turn the top oven switch on to the first setting as well as operating the grill control).
To prevent the grill being operated with the door shut, there is a micro-switch on the door hinge that allows the grill to operate ONLY when the door is down. The grill control also does not illuminate unless the door is down. There are two options on the grill control - right or left. One way is the inner element only and the other is both inner and outer ones.

Hi,Everything operates normally, but the oven shuts off after varying amounts of time. This could be a faulty magnetron, bad cooling fan (or just built up dust and grime block ventilation grilles), bad thermal protector, faulty controller, some other intermittent component, or bad connections.

• If resetting it allows cooking to resume immediately, if even for a few seconds, I would not suspect the magnetron or thermal problem as no cool down time is required. It could be bad connections in the controller or elsewhere, a marginal door interlock switch, or a controller problem. Jiggle the door to see if this will cause it to shut off.
  
• If the magnetron was overheating, you would not be able to resume cooking until it cooled and the thermal protector reset. If it just stopped working (i.e., the filament opened), everything would appear normal but there would be no heating. If the magnetron were shorting, there would likely be a loud hum associated with the periods where there was no heat.
  
• If it is not possible to resume cooking for a few minutes indicating that something needs time to cool off, then the magnetron could be faulty but check for the obvious cooling problems first: blocked or dirty ventilation grill. Determine if the magnetron cooling fan is operating by listening for its sound or looking through the ventilation opening in the back of the oven. If it is not, there could be a broken or weak belt, gummed up or lack of lubrication, other mechanical problems, a bad motor, or bad connections.
  
• Extremely high power line voltage may also result in overheating on a poorly designed or oven where the components are marginal.
  
• Make sure the stirrer fan is turning normally. Should it gets stuck, some models may sense this and shut down/restart.

Hope it helped..
Thanks for using fixya....

grill switch will not turn on grill

check your manual if you don't have one check the internet for your model and download and then print it out.

Is the cooling fan running in the oven? Does it also continue to run when the oven controls are turned off to let the oven cool down?
There are ventilation grills below each door on the oven. You can see these when the doors are fully open, just look under each door to see if they are clear and not blocked up.

if your oven is fairly old, dust might be the enemy. FIRTS Turn off the breaker on your house electrical panel that feeds power to the oven before doing anything. Do not electrocute yourself!!

Remove the control console bezel where the control panel for your oven is..it's probably held on by a few screws. You'll see the fan is there somewhere inside the enclosre, it's purpose is to keep the circuit board cool but the fan grill is probably clogged with dust...remove the fan from the enclosure...try using a vacuum to get the dust out...you might need to use a small brush to loosen the dust film, clean the fan blades while you're at it. Reassemble and turn on the power ...you'll probably find the fan runs much quiter...good luck