old man roger

so on my bike i took the two wires off the tempeture sending unit and put a switch in between them so i hit the switch and the fan comes on....

if i were to hook the two wires back up to the sending unit but leave the switch also hooked up would that let my fan come on if i forgot to throw the switch ?

sounds good if i understand this correctly

any one know for sure if this will work?

Mr. Hooligan

If you got the switch wired so it is used like the temp. unit it will. I mean the wires still go the way cowi. put them but you add the switch in the path so its just extra.(tap into each wire not cut and terminate) If you you hit the switch it complets the ground if you dont it waits for the temp switch to do it.(Think T-splice conector on each wire) I've done this on a few of my cars that I switched to a electric fan and it works good.


Roger I know you know how to do it I just put in the tec. stuff to help others who don't

old man roger

well i thought it would work but i never tried it, but im gonna....

thanks for the reply

Scott-

how do i do this mod on my f4i and what kind of togo do i need ? i was lookin at pepboys and they had a **** load of togo's.

MikeM

if your switch is in parallel with the factory switch, it will be an "or" situation

old man roger

and on an f4i i think you just put a 12v toggle switch between the sending unit and ground

MikeM

there is a black wire that goes between the fan motor and the thermostat. When you ground that wire, the fan comes on, so tap into it and run it to a switch. You need a 'single pull single throw' switch

Street Warrior

I think you put the toggle switch between the fan and ground, since all the sending unit does is complete the circuit between the fan and ground. So if the switch is off and the thermo's hooked up it'll complete the circuit and your fan'll turn on when it gets hot. only way to wire it is parallel, the switch in series wouldn't do anything except prevent it from turning on when it got hot. btw it's 'single pole, single throw' :

old man roger

if the sending unit completes the circuit then a wire from the sending unit to the switch and from the switch to ground should work then on an f4i

Street Warrior

no because the sending unit would still need to hit it's temp before the circuit would be complete, and the switch would need to be on also, and the only thing the toggle could do is prevent the sending unit from working

EDIT: well actually it depends what side of the sending unit you're talkin about, if you're coming off the side that's conected to the fan then yeah, that's parallel. if ou're putting the switch between the sending unit and ground, no, that's series.

old man roger

i thought an f4i sending unit only had one wire.......ground that wire and the fan comes on

Mr. Hooligan

ok here it is on the one wire bikes find the wire that go's to the temp switch and T into it with another wire and your switch then put the other side of your new switch to ground . you will have full control and still have the temp. unit for back-up If you forget to turn on the fan.

Street Warrior

I don't know about the F4i specifically, but how could anything work with only one wire? It might have only one wire from the fan going to it, but it has to be grounded somewhere else.

As long as the switch you put in is coming off the wire between the fan and the sending unit, to ground, it'll work. Just also leave the wire hooked up to the sending unit and that'll work too when it gets hot.

old man roger

thats what i said ....i think ...lol

old man roger

the sending unit must ground to the radiator when the temp gets high enough

Street Warrior

what r6-hooligan said, you need to T it before the sending unit, that way either the switch can put power to ground, or the sending unit can. If you just took the wire off the sending unit and put it on a switch, obviously it wouldn't work when it got hot and you forgot to turn the switch on...

Mr. Hooligan

Just went and red your posts and ya you did say that

Oh well some need to hear it from more than one source before its correct

old man roger

basicly what i said

old man roger

hahaha we posted at the same time

Street Warrior

that's how it is on the 900 too