Hello dwight, welcome to Fixya.
I see you posted here a couple of days ago so I`m not sure if you still need a solution, but in the event you do, this should move you to that, or closer to a solution at the least.
The "F5" error code on Asko dryers is indicating a communication fault between the moisture sensor and the control, typically caused by lint build-up on the sensor itself...that`s the best case scenario anyway.
The first step in this process is to gain access to it and clean it, and here`s how...
1) you`ll need to remove the lower panel to which you will then reveal a plastic cover over the blower housing. Located on the housing you will find the moisture sensor usually hidden under some black puddy.
2) Remove the gum type puddy and there you will find the sensor held in place via single screw, a very small torx head...#10 I think, pardon me it`s been a while.
3) Remove the sensor and clean it out best as you can. **It will resemble a thimble one would use for sewing, see below**.
Re-install the moisture sensor and give it a test. If that fails to remedy the problem you may indeed require a new sensor, but I`ll tell you how to check it first.
** Unplug the dryer from the wall or turn off the breaker **
Remove the plug of the sensor ( it`s a small board plugged into the main control board so it is a bit involved to gain access to it ) and with the aid of an ohmeter measuring accross the sensor should supply a reading of 40 - 60k ohms ( thousands ) at a temperature of 86°F - 68°F. ( 20°C - 30°C ).
Unfortunately you must do the measuring at the integrated board to which the sensor leads are soldered to. I`ve attached the image below of what to look for.
**You`ll also want to check for any wire`s which may have gotten severed from rubbing against the drum or the like. An open circuit will cause the F5 error as well, so you want to be sure it isn`t simply a wire cut or something simple such as that.**
Having said all that you may find it overwhelming and decide to call a pro. May I suggest if you do, check around for a service company familiar, or even better an authorized servicer of Asko products, they may cost more but save you more in the end.
Hope this was useful to you and thanks for choosing "fixya". Please take moment and rate the info I provided for you here today and a testimony if you are happy with the solution. Let ME
know if you are not and I`ll try to assist you further.