From your description of the cooling fan running all the time it sounds like you have a WFCO as the fan is amperage controlled. You can replace it with a Progressive Dynamics which is a 4 stage and you will probably never hear the fan as it is temperature controlled. Your batteries will thank you.
Your converter will sense a low battery and increase the charge as needed. If the fan is running constantly it may be sensing low batteries and perhaps the batteries are due for replacement.
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