Radiator Fan Questions ~ SOLVED

[Questy]

TLDR:
1985 1.9 Westy Factory A/C.
Van overheated this weekend -boiling coolant! -- radiator fan didn't come on when it should have.
I Tested at the sensor plug at radiator ala Ken Wilford (https://www.vanagain.com/troubleshoot-your-radiator-fan/). NO Power, NO fan!
Here's the wierdness: Van has factory AC and FAN COMES ON WHEN I TURN ON THE AC so clearly the fan and circuit work!

Details:
So we drove up a very big hill this weekend (Sea Level to 5K Feet over 17 miles). Hottest day of the year, biggest climb ever tried to highest altitude...super steep road--coolant boiled over and the fan never came on...but comes on when I turn on the A/C.


I'd love some ideas on where to start trouble shooting this....thanks in advance

SOLUTION: it was suggested by Ken Wilford I check the #7 fuse--which was fine. This lead me to checking the wiring on the backside of the panel, where the #7 post was disconnected. Once I reconnected it: Shazam!!! All good.

Required eye candy of van in a cool place:

[davevickery]

The AC bipasses the fan switch in the radiator, so that points to a bad switch most likely or an obstruction, possibly crud in the radiator or less likely partially stuck closed thermostat.

But you tested the fan directly by putting a piece of jumper wire into the plug like in that vanagain post? Maybe explain better what you did and what you saw, or just pull that plug and try the jumper thing again. If you can get the fan to come on both speeds with the jumper, then you either have an obstruction in the radiator that is preventing the switch from seeing hot coolant, or the switch is bad.

[shagginwagon83]

http://www.gowesty.com/product-details.php?v=&id=3651

Radiator Fan Temp Switch. I'd look at this bad boy. This is what was wrong with my system. I have the 83.5 with factory AC. I think I need to replace my radiator also because it sometimes takes it awhile to kick on.

[Steve M.]

disconnect the radiator fan switch and jumper the connections.
If the radiator turns on it is the switch.

Like this:

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[Questy]

Thanks for the replies.

So I've tried jumping the plug...no fan. So I put a multimeter on it, no Volts. But 0/53/35 Ohms resistance.

Because of the overheat-boiling lost coolant, I topped/bled the cooling system.

[Questy]

SOLUTION: it was suggested by Ken Wilford I check the #7 fuse--which was fine. This lead me to checking the wiring on the backside of the panel, where the #7 post was disconnected. Once I reconnected it: Shazam!!! All good.

[Wildthings]

[Wildthings]