Broke my radiator fan switch taking off passenger side exhaust manifold of my 85 TA 305 tpi. Mine is the 5/16 unit but RockAuto and other places also list a 9/16 unit (diameter of sensor end that goes into the head) As far as I can tell they'll both thread in. Wondering what the difference is between the 2 sizes because to replace my 5/16 unit is $40... but the 9/16 unit is only $10.

 

Should be 3/8 npt sizing

 

yes i know that.. I'm asking the difference between the 2 sizes of the sensor end of the unit

 

Are you referring to the button head size on the switch?

 

here's a pic of the 2 sizes.. just want to know what the difference is.. why are there 2 sizes? can I use either?

 

If the only difference is the tip of the switch diameter and both are 3/8 npt and same button head either should work. Might opt for best quality or get a wells sw555 or equivalent. A single wire spade from summit racing at lower on/off temp is a option as well

 

Looks to me like the difference is either the height or the size of the part that goes into the water jacket.

The difference is YYYYYYYYYUUUUUUUUUUUUUUJJJJJJJJJJJJE.

5/16" = .3125"
9/16" = .5625"

The tip of both is obviously the same diameter anyway. They use the same connector. The # isn't the dia of that.

Looks to me like you could use either one. The shorter would probably be a better fit, at least would be more out of the way of everything else around it. But it probably doesn't matter in the slightest.

 

I'd opt for the 5/16 which is what the stock switch looks like....... the 9/16 might impede coolant flow.