CPU fan header bad?

[Benjydog]

I have a biostar a78ol3g and my cpu fan plugged into the fan header spins slowly (maybe a few hundred rpm) (4pin fan) or a 3 pin fan either “ticks”/“jitters” or won’t spin at all.  
 

plugging the 3 pin fan into the system fan header or via molex adapter direct to the PS makes it work no problem.  The system fan header only fits a 3 pin so can’t test there but it works 100% with the molex adapter. 
 

many idea if it’s a bad cpu header?  Only reason I want to investigate is for fan throttling as it runs full speed all the time. Would like to keep idle noise down when possible. 

 

thanks in advance. 

[bmx6454]

sounds like a motherboard fault. doubt it will help, but you could try clearing the cmos to rule out any weird settings issues. might also want to try reseating the cpu, seen this cause weird fan issues on older builds before.

[kb5zue]

Before you condemn the mobo to the land of recycle, maybe you should try a "new" fan first.  Fans are known to go bad in both directions, north and south.  Just try a different fan on the header first.  A fan that is known to be good.

[Benjydog]

Will try resetting the mb latter after work.  Didn’t think of that.  As for the fan suggestion that’s the same I first thought but unfortunately it’s the same result on 4 different fans (new and old)

 

either way if these don’t work, I’ll leave them powered by the ps.  My amd phenom is x4 965 black is still running strong after 10 years so no rush to replace (yet)