I replaced safety switch then transmission stopped working

Most likely a bad belt. Contact Consumer Care at 1-800-237-7691 to order parts (detailed instructions comes in the package. To open the Belt area access panel you will need a flat medium sized screwdriver. There are two slots on the right hand side of the unit. Push the screwdriver into the lower slot and press the holding tab to lift the panel. The top tab should slide out easier but if it doesn't use the same process as the lower one. Examine the belts by rotating them all the way around (there may be two belts in your unit). I'd recommend if one belt is bad to replace both belts and keep the used one as a spare. Good luck. Hope that helped.

the problem may be either the hose or the spout[the area where connect the hose.Start the vacuum and twist the hose around especially near the end that connects to the wand.If it starts and stops it is probably the hose.....please get back to me if this doesn't help...Chris

You changed the belt that drives the brushroll, it is a flat stretch belt. The V belt also should be replaced every year or two max. It will not be stretched out like the flat belt but with normal use the side of the v will of wear off and the belt will be a little thinner which can cause it to slip on the pulley. The V belt drives the transmission. The flat belt goes from the transmission to drive the brushroll. The burning smell could come from the V belt if it's slipping real bad.

there will be a linkage that as come loose and not operating the limit switch to turn it off, try looking at 23. Idler Clamp Assembly on the link below.
http://www.vacpartswarehouse.com/Eureka-4870-Ultra-Smart-Vac-s/1928.htm

Is the PN motor not working, or just the brush not spinning. If it's the brush, a new belt is needed.
If the motor isn't working, it could be due to several things. Follow the trouble shooting steps below.
1. Check all connections from hose handle to PN for discoloration. Any parts showing discoloration or melted plastic need to be replaced.
2. Attach PN directly to the hose. If the motor works, there's a problem in the wand wiring/connections.
3. Attach the Sidekick directly to the hose. If it works, but the full sized PN doesn't, there's a problem in the PN. Problems could include: wiring, connections, bad motor, bad switch.
4. If neither Sidekick nor PN work, the problem is likely in the hose. Potential problems include: bad wiring, connections, or bad switch.
5. You can try another hose known to be good to test the PN. If it still doesn't work, the problem could be in the canister itself.

I strongly recommend taking it to an authorized Aerus Electrolux store for diagnosis and repair if needed.

http://www.aerushome.com/storelocator/

Knowing the model would help.
Possible problems:
Broken or disconnected wire in hose, connections, power nozzle.
Hose needs replaced. Check all connections for discoloration and cracked supports. Have power nozzle checked at a vacuum shop. Depending on the model, take it to an authorized Aerus Electrolux store for this.
Bad power nozzle motor Needs replaced.
Bad switch. Take the whole machine in for thorough check and repair..

Hi
The motor spindle should NOT rotate when there is nothing attached to the front. Its very dangerous. There are two square switches on the front of the machine which engage depending on wether its the main head or hose thats attached. Looks like on of them is sticking
Rob

Take it in to be serviced. It could be a dead motor to bad connection. 5yr warranty will leave you paying nothing. Best Buy or local authorized service center can do it.

I would take it into a local vacuum shop but DONT take it to a kirby shop because they will charge way more

take the cover off to get to the wiring and check the brushes - that is where the clear-insulated black & green wires terminate at the motor sides under the plastic caps