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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 1980’s Toyota Corolla’s. 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 Volvo’s 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 Volvo’s 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..

Parts required:

10 inch electric fan, shroud and wire harness including modular connector from early to mid 1980’s 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)

Misc. supplies:

  • 14 gauge wire
  • Electrical and wire clips
  • Paint
  • Metal for braces

Tools:

  • 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.


Toyota fan

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 sides.

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.


Completed assembly

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

Results

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 rpm’s. 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.

 

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