I installed a SLP fan switch this weekend and was wondering if it would cause a problem if the fans ever switch got switched "on" while the fans were already operating on their own.

 

unlikely

 

ive never had any issues doing so

 

There is no problem about doing this. I have done it several time and this manual switch had been a great help when i had overheating problems.

The only problem is that the fan will still operate if you turn the engine off while the switch still on and there is even not a single light to warn you about it.

Pierre