[Lumps!] cooling fan fuses, was voltage drop and other interesting experiences

Where in the circuit did you add the new fan ? And are you blowing the
voltage supply fuse at the headlight relay box or the control-side fuse
under the dash ?

The 87A terminal is seen on a switchover relay. It is normally an output
terminal which turns “off” when the relay is energized. However, in the Jag
fan circuit (at last on the Ser III XJ cars—I can’t remember what you
have) it is not used that way.

I’m not sure what the Jag relay is rated for, or how much power the Jag fan
draws, but you may need to run an additional relay.

Did you hook your new fan up to the green/blue wires or ??

Doug Dwyer
Longview, Washington USA

I found an electric fan at
the wreckers from an 82’ Firebird that seemed to suit the dimensions.
After
a small amount of modification of the existing fan shroud the new fan fit
like a glove. After some research on the lists I was able to wire the fan
through the existing auxiliary fan relay circuit.

However, as I still have the small aux. fans, I attempted to keep
them in the loop, so to speak. Result - blown fuses. I checked the wiring
and short of a rewire I could find no problem. OK. So I decided to run a
new
10 gauge wire to the front radiator wall in the hope that the resulting
better supply would solve the problem. No change, still blowing fuses.

Q. In running the new wire what fuse would be recommended. I keep blowing
a
20 amp when I hook the aux. fans up. Is the draw to much or would this
suggest a short that I just haven’t discovered yet?

Q. What is the function of the 87a terminal on the existing relay?

// list policy dictates that messages be trimmed----- Original Message -----
From: “Steve at North Island Restoration Ltd.” NIREST@mars.ark.com

Where in the circuit did you add the new fan ? And are you blowing the
voltage supply fuse at the headlight relay box or the control-side fuse
under the dash ?

-Thanks for the reply Doug and Walt. At present I am finishing a Lumping job
started by the PO. It is Chevy 350/350 in a 1978 xj6. Originally the
mechanical fan was a large flex fan - very noisy. The auxilliary fans x2
were wired into the headlight wiring to come on only when the lights were on
??? So the fans were controlled through the headlight relay but the power
was fed from the horn relay. On the series II the horn relay is on the right
side of the rad while the headlight relay is on the left. There is a second
relay (red)in the same area as the horn relay on the same mount. I was not
sure what this was for - maybe the air conditioning, which is not there.
Anyway I wired my new fan through this relay. The control wire is fed from
the horn relay - live when ignition is on, and for power I fed a new wire
through from the battery. Everything appears fine as long as the aux. fans
are not powered. As soon as I run power to them (from the voltage feed on
the relay)I blow the 20a fuse in the power supply side. Walt also responded
to my questions and suggested that “I wasn’t thinking right”, but also the
amperage draw maybe to much. This seems to make sense as well.Auto electrics
are new to me so I’m on a sharp learning curve here. Also of interest, I
couldn’t get the fan to work when I wired the rad mounted thermal switch
through the gound wire. It needed to be in the control wire circuit. This
still doesn’t make sense to me, but it works.

The 87A terminal is seen on a switchover relay. It is normally an output
terminal which turns “off” when the relay is energized. However, in the Jag
fan circuit (at last on the Ser III XJ cars—I can’t remember what you
have) it is not used that way.

  • At present the 87a terminal is bare - nothing hooked up. Is this OK?

I’m not sure what the Jag relay is rated for, or how much power the Jag fan
draws, but you may need to run an additional relay.

Are you suggesting a seperate relay for the aux. fans only? If so, I could
run another power wire easy enough but would it be OK to use the same
control circuit.

Did you hook your new fan up to the green/blue wires or ??

Yes.

Steve Chatwin.
1978 lumped XJ6 with Chevy 350/350

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