DUAL ELECTRIC FAN CONVERSION
by Ian Giles
Everyone with some automotive knowledge believes they can improve upon how
their car was originally manufactured, whether that is the engine HP, suspension
and handling, appearance
the list is endless. The following article outlines
the conversion of my 1989 Volvo 744TI from the stock mechanical engine cooling
fan to twin electric fans from early to mid 1980s Toyota Corollas.
The reason for this conversion was two fold but simple; 1) to reduce engine
power loss from the fan, and; 2) eliminate the noise of the stock fan which
I found very annoying and contradictory to the "performance" image
of my Volvo.
Originally the 700 turbo Volvos were equipped with a 12" electric
pusher fan to supplement the belt driven engine fan, in this conversion the
stock electric pusher fan is retained and two additional puller fans are added
in place of the mechanical unit. One of these fans runs constantly while the
engine is running with the second fan activating when the radiator temperature
reaches 180° F.. I have also included an alternate wiring diagram that will
allow one fan to run after the engine has been turned off until the radiator
temperature drops below 180 deg F. Since all Volvos use the same radiators
this conversion could be used on any year and model.
The reason for using this fan configuration is primarily cost and cooling efficiency,
total costs were less than $50.00 Canadian (that is very inexpensive in US dollars).
The fans are very easy to obtain and efficient cooling performance for varying
temperatures, which in my region vary from -40° F to +95° F..
10 inch electric fan, shroud and wire harness including modular connector from
early to mid 1980s Toyota Corolla FWD (2 required) $6.00 each from auto
wrecker. Fan shroud made at local sheet metal shop.$14.00 180° F Electro Thermo
switch from auto parts supplier $20.00 Dual 12 volt relay (not sure of price,
I had one in parts box but probably $10.00)
- 14 gauge wire
- Electrical and wire clips
- Metal for braces
- Regular automotive hand tools
- Oxy acetylene torch (not required but helpful)
- Soldering gun
- Saber saw with metal cutting blade (or hacksaw and strong arms)
Step by Step Instructions
Step 1 Remove fan and motor assembly from fan shroud,
measure and mark the circumference of the shroud with masking tape one inch
from back lip. Cut the shroud along the mark, you will end up with a narrow
circular rim with the motor mounts and braces connected. I used an electric
jig or saber saw with a metal cutting blade.
Fan mount cut out of shroud
Step 2 Have your local sheet metal shop bent two circular
hoops 2 inches wide and a diameter that snugly fits around the OUTSIDE of the
shroud cut in step 1. Have the hoops spot welded and then spot weld the two
hoops together to form an "8" (see picture #2). My local shop charged
me a total of $14.00. I used about 12 to 14 gauge non-galvanized metal to accommodate
painting and brazing.
Step 3 On a piece of paper or cardboard mark out a
rectangle the same dimensions as the radiator it will be about 17 inches high
by 18 inches wide, this will be used as a template to align the mounting brackets
and fan mounts before connecting them.
Step 4 The next step is to make the mounting brackets,
the unit is mounted the same way as the existing plastic fan shroud. The bottom
is a "U" shaped channel that slips over a ridge on the bottom of the
radiator, the top is a flat bar that connects with two screws.
I fabricated the bottom bracket out of a "V" shaped support used
for wire closet shelving. First cut off both ends that were flattened to accommodate
mounting screws and strip the paint off (I used a wire brush on my bench grinder).
Next I inserted a 1/8" piece of steel into the "V" and then compressed
it in a vice to produce a "U" shape with 1/8" between the two
The top bracket is made out of 1/8" X 1" flat steel 14" long.
Mark and drill the screw holes so they align with the existing holes on the
top of the radiator. On the paper template mark the hole locations and the location
of the lower radiator shroud mounting rib, this is approximately 16 3/8 inches
from the top to bottom. Position the metal hoops on the template along with
the top and bottom mounting brackets so they are aligned with your marks. The
fans are arranged diagonally on the radiator, one on the upper left and one
on the lower right. Carefully install the electric fan shrouds you cut in step
1 by aligning the "top" of each and inserting into the metal hoops
making sure they are snug and level.
Weld or braze the motor shrouds to the hoops first, next I reinforced the spot
welds between the two hoops by brazing the hoops together. Finally weld or braze
the top and bottom mounting brackets. If you do not have access to a welder
the electric fan shrouds could be fastened to the metal hoops with pop rivets
or solder. The mounting brackets could also be bolted or riveted using simple
"L" brackets between the hoop and the mounting brackets.
Test fit the assembly to ensure everything lines up. You may need to grind the
upper fan shroud slightly to provide clearance for the upper radiator hose,
or protect the hose as I did with a short section of 2"PVC plumbing pipe
cut in half and secured to the upper radiator hose to prevent potential rubbing.
Finally clean and paint the completed shroud assembly and install both electric
fans into the unit.
Step 5 The electrical circuit uses a dual relay and
a temperature switch to control the fans independently. I have included two
wiring diagrams, #1 where the lower fan runs any time the engine is running
and the upper fan comes on when the radiator reaches 180 degrees F., but neither
fan is operational when the ignition is turned off. And #2 which operates the
same with the exception the upper fan will operate any time the radiator temperature
is above 180 degrees F. no matter if the ignition switch is on or off. Test
run each fan prior to final connections as these fans will run backwards if
they are wired in reverse.
Use at least 14-gauge wire; solder all connections and seal with tape or heat
shrink tubing. Use wire tie wraps to secure the wiring to avoid rubbing or contact
with moving parts.
The source for ignition power is the positive terminal on the ignition coil,
the relays draw a very low current and will not effect the ignition at all.
Main switched power comes directly from the battery. I mounted the relays on
the left inner fender
This conversion has been running perfectly with no problems or surprises. I
have not noticed any differences in how the vehicle cools, the second fan (temperature
controlled) cycles on and off when driving hard or in heavy stop and go traffic,
the factory electric "pusher" fan seldom operates. This seems to indicate
sufficient cooling is being provided.
The largest improvements are in the areas of reduced noise and increased power.
These fans produce very little noise, in fact you can barely hear them with
the hood closed, this is a real change from the original fan that created enough
noise to drown out engine sounds. The biggest surprise and benefit is with power.
There is a noticeable increase in available power at higher rpms. With
my AW71 and the factory fan, power would flatten out at about 5000 5200
rpm and there would be a slight delay on upshifts. With the electric fans the
power increase is constant to the shift point with no delays.