Negative cable on V8 radiator fans question.

[andyblackman777]

Hi,

I’ve fitted new fans onto my V8 rad. There is a separate positive and negative. wire to each fan motor .The negative wire also connects to each fan housing, it’s just a splice from the motor connector.   The wiring diagram shows the fan motor negative wires going back to an earth post and also the second negative also connects to an earth post. The odd thing is that the radiator is housed in a grp  tray, so no earth connection??

Do I need this second negative?

Cheers

[LotuStuart]

Theoretically no.

Perhaps the fan housing is also used by another item (the horns??) as an earth.

I'd connect it up anyway-no harm done.

[Chillidoggy]

What does the wiring diagram show?

[sailorbob]

On the wiring diagram I have there is a single -ve wire going from a single -ve post to 'rad fan splice B'. From the splice a further three -ve wires go to each fan where each -ve wire is connected to both the 2 pin connector and fan housing.

[andyblackman777]

Derek yes thats whats confusing me. I don't understand why the -ve wire goes from the fan motor to the fan housing. Maybe a requirement of the old fans?? Or maybe thats the way all of the earths are joined, the splice is the fan shroud?

V8 fan wiring diagram. From the workshop manual.

 

[sailorbob]

If your new fans are plastic bodied then do not bother with the -ve to the housing, just tape it up out of the way. The -ve wire to the metal bodied fan is probably just there for the purpose of reducing electrical interference.

[snowrx]

Perhaps they were thinking of reducing any galvanic potential between dissimilar metals that might corrode the radiator?

[Chillidoggy]

I have a sneaking suspicion that the S4s wiring was the same, and if so I was probably scratching my head wondering why at the time, but it’s a while since I did the rad pack and I’d have to look at the wiring diagram.

[Chillidoggy]

Found it.

And no, I don't know, either.

[andyblackman777]

Thanks for all the replies. I think Derek might be onto something.

Anyway I effectively connected the extra earths together by bolting them to the new Spal fan securing bolts, which go through the radiator frame. So it’s basically the same as before.

lets hope they work......🤔