gator79

I am in the process of wiring the dual Spal fans on my Dewitts radiator. the switch came installed in the radiator tank. Seems like the radiator itself would need to be grounded. If the switch simply closes at say 195 degrees the control wire for the relay becomes connected to the radiator thru the thread connection. the control wire needs to be grounded to close the relay correct? if it is mounted in the block it goes to ground thru the engine block.

doorgunner

Rookie reply: If the switch has only one wire terminal, it seems the tank would need to be grounded to the frame........

if the switch has two terminals----one terminal would be for 12V+, and the other terminal would go to a frame ground ( or to a fan relay), depending on how the relay was wired into the fan harness.

gator79

it is a one wire switch

gkz

I ran a discrete ground from the radiator to the frame, otherwise the ground is via the tranny cooling lines.

0Tom@Dewitt

All our combinations (rad/fan) come with a ground strap attached to the bottom rail. Just for this reason

Shark Racer

Wouldn't this cause a direct short?

I would assume the switch is for closing the connection.

IE terminal 1 goes to relay, terminal 2 goes to an appropriate (read: keyed) 12V source. So the relay is energized when the switch closes.

If terminal 1 goes to ground and terminal 2 goes to 12V, as soon as the switch heats up and closes you'll be sending 12V directly to ground.

You could alternately wire it ground to ground, but if you use it for switching a 12V source then you could set it up to always energize the fan when the AC clutch switch is hot.

doorgunner

It definitely depends on how you wire the harness....

Ign. ON/12V to 2-terminal switch...then 12V out from switch to relay activation terminal.......(relay directs constant 12V from battery to the fans)

OR

Ign. ON 12V to relay activation terminal/relay ground terminal to 1-terminal switch (relay activates and supplies constant 12V from battery to the fans/radiator is grounded through supplied grounding strap to frame or through fabricated grounding strap)

It is easier to understand when viewing wiring diagrams....

HOWEVER...... since your switch is 1-wire, the easiest thing to do is run the ground wire from the RELAY to the 1-wire switch.



#30 wire......12 gage

#87 wire......12 gage

other wires...16 gage

Have someone confirm this diagram, since I am a rookie....LOL.

Shark Racer

Your new post is good - first post was a little off cuz it reads like you're connecting a 12V source straight to ground via the switch.

Wiring diagram looks excellent. 87 connects to 30 when there's a potential difference between 86 and 85 (you can flip the connections between 86 and 85 with no difference).

When there isn't a potential difference between 86 and 85, 87a and 30 are connected.

AirborneSilva

Tom, not arguing with you but I have one of your radiator/fan setups and don't remember a ground strap, do you have a picture. For what it's worth mine seems to be working just fine...

0Tom@Dewitt

I don't have any pictures but it's just a 14ga wire with eyelets on each end. We may have missed your rad but all rads with the switch in the end tank should have a ground strap somewhere. The switch uses the body as a ground and if the radiator isn't grounded, the fans will never come on.

AirborneSilva

My fans do come on and seem to work fine, I'll look at it to see if there's an obvious place I can run a ground wire...