I understand your concern. You have already received some good information. From the information listed, it would appear the defrost timer # 482493 will need to be replaced, to correct the defrost problem.
Now, if the fans are running slow, the lights dim and the unit is not cooling, I suspect the compressor is not running. If the compressor is trying to start but can't, it will draw the current down and can cause the motors to run slow and the light to dim but this will only happen momentarily until the compressor overload opens. Then it will happen again, each time the compressor tries to start. If this is taking place the problem could be with the starting device on the compressor or the compressor could be locked (stuck). A technician will need to make this check.
Another possibility could be a poor wire connection. The voltage will also need to be checked where the power cord connects to the refrigerator and at the wall outlet. These checks need to be made with the refrigerator still connected. I recommend having a technician make these checks. I'm listing a site you can access, to have a tech come out. Here is a link for the website:
Sears Home Services
. If the problem is at the wall outlet, an electrician will be needed. If you would like more assistance, any additional details will be helpful and I will be glad to assist you further.
: Be sure to disconnect the appliance before performing any troubleshooting procedures. If you are not comfortable with doing any voltage checks or repairs that might be recommended, please contact a local service provider for repairs. Be aware that there could be sharp edges inside the appliance that could cause cuts or other injuries to yourself or others.