Thermo fan switch

[Bill Cleveland]

I have an electric fan with a thermo switch located in the intake manifold next to the water neck. It is rated to turn on at 185 and off at 170. However, when driving in hot weather, the fan will not come on until the temp gage reads 210. Suspecting a faulty switch, I replaced it with another rated the same, with the same result - no fan until 210 degrees indicated. The engine has never overheated - no boiling & such - and stays below an indicated 200 as long as I am moving, so I'm wondering if my gage is not reading accurately. Any ideas?

[dezolde]

Don't know where you've got sending unit to temp gauge located. One thought might be to switch the locations for fan and temp sending units and see if you get same or different results/readings.

[Bill Cleveland]

Temp gage sending unit is just across the manifold, also near the water neck. Should be reading the same water temp.
.
(In the pic below, the temp ga sending unit is on pass side of manifold,
and the fan switch is on driver side.)

6 Engine2.jpg (43.76 KiB) Viewed 1617 times

[dezolde]

Thanks for the reply. My earlier response only offered to diagnose different locations of each sending unit. Given their locations, that would not appear to be a problem. IMO, more likely, the issue might be the temp gauge itself. An possibility you might have additional/spare/extra temp gauge that you might be able to hook up and compare?

[Bill Cleveland]

IMO, more likely, the issue might be the temp gauge itself.

That's my suspicion as well; no spares available, but . . . I'll just live with it for awhile. Thanks

[mike wade]

IMO, more likely, the issue might be the temp gauge itself.

That's my suspicion as well; no spares available, but . . . I'll just live with it for awhile. Thanks

Spanky I have a manual temp gauge I will ship it to you and then you will know.....it is still wrapped up like it was when Lavelle Tunnell sent it back after they checked the electric one in their car a year or so ago.....Just let me know....

[Bill Cleveland]

Update: the problem has gone away. Best guess? Some air bubbles in cooling system. All good now

[mike wade]

Update: the problem has gone away. Best guess? Some air bubbles in cooling system. All good now