Air trapped in the system could cause this problem, especially if the person working on the bike was not real familiar with intruders. there is a bleed hole in the frame- you have to remove the bolt from that hole when you change the fluid or air is trapped in the system. the bolt is on the right downtube, even with the top of the valve cover right at the bottom of the neck cover.
oh, and for what it is worth, I've owned three intruders- a 86 I sold after only 10,000 miles; a 1996 I put 135,000 miles on, and a used 1993 I bought with 7000 miles that now has 64,000 on it. The temp light never came on with any of them, and none of them overheated or ran hot, even in 107 degree temps in Texas.