Electric fan on a 1974 Triumph TR6

(with wiring diagram and notes from Dan Masters)

Task: replacing the mechanical cooling fan with a sucker electric fan. I was not content with the small 12" fans marketed by the Triumph vendors, but there is a clearance problem between the radiator and the front frame rail (about 3.5"). So choice of a fan to mount behind the radiator is crucial.

After much experimenting, I found that the PermaCool 16" 'standard' fan fits perfectly. The fan is just the perfect diameter so that I could use machine screws to mount it directly to the edge of the radiator. No need to make complicated straps, it is a simple bolt-on installation. I would advise NOT to use the through-the-radiator straps. These fans are heavy, and in time, will bend the fins and the fan will sag. The fan kit is supplied with some anti-vibrations pads, and I would suggest using them.

The only mounting problem with this fan is that the radiator has to be removed to install or remove the fan. The 16" fan costs $81.99 from Jegs (800/345-4545), part #771-19126. This fan blows 2250 CFM and draws 8 amps. Yeah, its a monster, guranteed to cool the hottest TR. You can see a picture of it at http://www.jegs.com/ and then find your way to the cooling section of the products page.

Further more, the crankshaft extension has to be cut down to 1.25", and the crankshaft pulley bolt shorted to 2.5". Rethread the bolt (18 threads/inch) to fit the crankshaft end Reinstall crankshaft extension. Be sure to replace the dowels between the crankshaft pulley damper and the extension. Safety wire the bolt or use lock-tite.

I did not want to use the cheesy thermoelectric switches often sold with electric fan kits, as I have heard a lot of bad stories (grounding, etc) about them. So while the radiator was out, I took it down to the local radiator shop and had them install at the bottom of the radiator a drain tap and a mount to which I screwed in a BMW thermoelectric switch. This switch is designed to come on at 91C (195 F), and seems to switch off at 82C (180F, when my thermostat closes). The BMW part (#1VT14AA231F1384272BMW 91c V2T) is pretty expensive, but only $25 from NAPA (part #ECH-FS198). But what do you expect of BMW parts?

I followed a wiring diagram prepared by fellow Scion and Triumph List member Dan Masters (danmas at aol dot com). This was quite easy to rig up, using a small 3-position DPDT switch I found at Radio Shack. This switch is tiny, and easy to hide - no need to drill holes in the dashboard, I mounted it just beneath the steering wheel, on the small metal lip behind the dash board. I am a real klutz at wiring, but this job was easy, and afterwards, I tidied up the wiring in the engine bay with tie-wraps and those split-hoses that you can buy just for this purpose. The whole underhood installation looks very neat, and something you can be proud of.

After installation, I backflushed the cooling system for 30 minutes using one of those nifty kits from Pep-Boys that enable you to hook up a household garden hose to the heater hose that runs from the block.

I dont use anti-freeze, as it never gets that cold in San Diego. Instead, I use my own special mix of distilled water, Redline Waterwetter and PenCool (used to be NalCool). How does it work? Rags has to sit in traffic in at least 85F air temperature for 30 mins before the fan switches on. The fan switches on at the advertized 195F (the 3/4 mark on my temperature gauge), and in less that 60 seconds, the temperature drops to below 180F when the thermostat closes and the fan switchs off. Thats what I call cooling! The fan has never come on when the car is moving.

The real benefit of this mod is that under acceleration, I dont hear the mechanical fan anymore, just that meaty sounding six screaming up front, pounding through a 2" pipe to the Ansa mufflers. Ahhhh, life is good!

Notes from Dan Masters (danmas at aol dot com)

click to enlarge wiring diagram

1) the relay can be mounted any where that is convenient.  The only criteria
that is of any concern (other than protection from physical damage) is the
TOTAL length of wire from the Brown (or Brown/White) wire to the relay and
then from the relay to the fan motor.  This length should be kept short, but
as long as you use the proper size wire, it is not really important (assuming
you don't intend to mount the relay in the trunk!).  In my car, I bought a
relay with a metal mounting tab, bent the tab and mounted the relay under one
of the screws that fasten the existing relays to the bracket under the hood.

2) connect to a Brown/White wire in a car with an ammeter (this is so that the
ammeter will read correctly), or to a Brown wire in a car with a voltmeter.

3) the fuse in the lead to the Brown (or Brown/White) wire MUST be placed as
close to the connection to the Brown (or Brown/White) wire as possible.  If
you do this, the remainder of the wire will be protected, and routing becomes
less critical. HINT:  If you detest un-necessary splices as much as I do, you
might try this trick.  I buy heavy duty in-line fuse holders from the auto
parts store and modify them to suit my purpose.  I cut the leads off to about
an inch and strip off all the insulation.  Next, I remove the fuse contacts,
and the wire, from the holder.  I place the contacts in a vise and spread the
wire strands out in a fan shape.  Using a pair of needle nose pliers, I pull
the center strand out of the crimp on the contact.  After a few of the center
strands are removed, the rest come out easily.  Once all the wires are
removed, I spread the crimp just a little, and insert the end of the wire I
wish to use and recrimp, followed by soldering.  This way, I get an in-line
fuse holder with the correct color coded wires, and each wire long enough to
reach the rest of the circuit without splices.

4) The wires used from the Brown (or Brown/White) wire to the relay and from
the relay to the fan should be sized to carry the rated current of the fan
with a little margin.  I would use 12 guage -- good for 20 amps -- unless you
are using a real horse of a fan.

5) the fuse MUST BE NO LARGER than the current rating of the wires used in 4).

6) if you wish to use the optional indicating light, you will have to use the
same size wire for the light as you use for the fan motor to ensure that it is
properly fused (or add a second fuse in the wire to the light, sized to suit
the wire gauge.  This fuse will have to be sized not larger than the current
rating of the wire, and placed as close to the relay as possible).  If you
prefer, you could connect the indicating lamp to terminal 85, along with the
other two wires.  Thgis way, no special precations are required, other than
listed in 8) below.  Wired this way, the light will tell you that the fan is
"supposed" to be on, but not that it is actually running.  The fuse could be
blown and you would still get an ON indication, even though the fan is not

7) When you connect to the Green and the Purple wires, you can use ANY Green
or ANY Purple wire you find, whichever of these wires is most convenient for
you to connect to.  Same for the Brown (or Brown/White) wire.

8) use at least 14 guage wire for the connections to the Green and Purple
wires, and you won't need to use a fuse in these leads, as the Green and
Purple wires are already fused.

9) You must use a DPDT switch; otherwise, if you have the switch in the ON
position and the thermostat switch comes on, the effect is the same as having
the ignition key on.  In this instance, power would be backfed from the purple
wire through the two switches and then back to the Green wire.  Since the
green wire is connected to the ignition switch, all the loads fed from the
ignition switch via the Green wires would be powered.  By using a DPDT switch,
wired as shown, the green wire is disconnected from the thermostat switch when
the DPDT switch is in the ON position.

10) there is a problem with the labeling of terminals on relays.  They are not
consistant in how the 87 terminals are labeled.  If you buy a relay with four
terminals, there is no problem, but if you buy one with five terminals, the
"center" terminal may be labeled 87, or 87a or 87b, depending on who makes it.
Sometimes the center terminal, regardless of its label, is a "normally closed"
or NC, contact ie, connected to terminal 30 when the relay is OFF, and
disconnected when the relay is ON.  The only way to be sure is to look at the
diagram on the side of the relay case to see that both the center and the
other 87 (or 87a or 87b) terminal are closed only when the relay is energized.
Luckily, it is very rare to find a relay with the center terminal as a NC in
an auto parts store (I have to special order them, and about half the time, I
get the wrong ones!).

11) if you buy a relay with four terminals, and still wish to use the optional
indicating light, just connect the wire to the light to the same terminal (87)
as the fan motor.  The same requirments in 6) still apply.

12) the physical configuration of the DPDT switch as shown in the connection
diagram is not important -- only that it looks like that shown when the wiring
is completed.  Wired one way, the fan will be ON with the switch handle in the
down position: wired the other way, the fan will be ON with the switch handle
in the up position.

13) if you wish to eliminate the ON-AUTO switch, just connect the thermostat
switch to the green wire, and eliminate the other wire to the relay terminal

14) if you buy the ON-AUTO switch at an auto parts store, it will almost
certainly have three positions - ON-OFF-AUTO.  If the third position is
undesirable, you will have to go to an electronics store, such as Radio Shack.
The only problem with this is that their switches usually don't suit an
automobile very well, from an asthetics standpoint.  You might want to hide it
under the dash somewhere.

This is all I can think of right now.  If you have any questions, let me know.

Back to my Triumph TR6 page

Last update: 11 September 1998.