Your model number seems to be missing the last digit.
There are KB0 to KB4 models. I sued the KB2 model.
They are probably very close if not an exact match.
Hewre are your parts.
Parts for Frigidaire FRS3HR35KB2 Refrigerator - AppliancePartsPros.com

Here is the tech sheet
http://manuals.frigidaire.com/p...f/Anderson/240389636.pdf

I also cant find the defrost timer, just the defrost therm, heater coil and the defrost switch
I do not know what the defrost switch is, could you please provide more info.

Your unit does not use a defrost timer it uses an adaptive defrost control board (item 23 in the Controls Parts section).

First remove the evaporator cover in the freezer so you can see the coils.
Do not let them de-ice.

If yes.
Manually force a defrost cycle, see the tech sheet When the fans and compressor turn off, you are in a defrost cycle.

Now check the defrost heater to see if it is on.
Be careful you do not want to burn your fingers.
If the heater is on then the timer needs replacing, as it is never getting into a defrost cycle.

If not on.
Unplug the unit.
Remove the wire for one side of the heating element (Item 14 in System Parts Section ) from the wiring and measure it for continuity, usually around 20 ohms or so.

If the heater is OK
Remove one wire to the defrost thermostat (Item 21 in System Parts Section ) and measure it, should be 0 ohms when frozen. Note that it opens just above freezing so must be frozen to check it. Also inspect it, if it is bulged at all replace it even if it measures OK.

If both the above are OK then odds are the defrost board is toast.

If you do not own a meter, I would suggest you purchase a one. You can get a decent digital multimeter for under $20.00. You do not need fancy though it is nice if the leads are a couple feet long.
If it saves ordering one unnecessary part it has paid for itself and you end up owning a useful tool.
Most places will not let you return electrical parts so if you order it, you own it.
A couple things to watch when measuring ohms and continuity
1. Always remove power from the machine otherwise you could blow your meter.
2. Always disconnect at least one side of any device you are checking. This eliminates the possibility of measuring an alternate/parallel circuit path.
3. When checking for closed contacts and continuity use the lowest scale (Usually 200 ohms). Then try higher scales. This scale is 0 to 200 ohms so if the device you are measuring is 300 ohms this scale would show an open circuit which it is not, you are just measuring outside the scale's dynamic range.
4. When you start always short the meter leads together. This will tell you that the meter is working and if there is any 0 offset.

There is a good STICKY at the start of this forum about it's use.

Ok i said i would let you know when i was finished. I know i am not the first for this to happen to but i am probably one of the first to admit it. After reading the post i got to work on trouble shooting the system thanks to the reply i got.. So i let the freezer build up a little ice then i clicked the light switch to turn on the defrost.. The heating element never got hot... So downstairs i went for my multimeter and back upstairs to the fridge... Putting a towel on the floor because i am old and i needed the padding for my knees i knelt down and proceeded to unhook the negative wire from the heating element then to the positive side... I barely touched it and it disconnected pretty much by itself..... Yep, in my hast to fix the fridge and be the hero in my house i never checked the wires to make sure they were solidly connected... After reconnecting the wire... As if the element touched the Sun it heated up like no ones business.... My cold box is fixed.... Moral of the story.. Check the wires to make sure all are connected!