horton fan issue

hi all, i have a problem with my horton fan not working, last week i found out that the fan was kicking in when it got a signal from the air conditioner but it was not kicking in when coolant tempt would raise, i replaced the fan sensor and it worked properly, but today the fan did not kick in again, so i tested the fan sensor and it is ok. i placed a 5/16 bolt into the horton to lock it up and was going to put another 5/16 bolt in when i got to my desternation, on arival i found that the bolt had snap off and that the fan was working again, so i left the bolts out. im thinking fan air electric soleniod?? may be on its way out?? any ideas out there??

 

Fixed the fan issue, and it was pure arse. I opened up the air valve that is near the fan soleniod and then gently taped it and the soleniod with a spanner several times, im sure some rubbish/dirt came out with the air, and now the fan is kicking in and out as normal.

Thankyou everyone for your advise, I love this forum