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E28 Electric fan install

Using Race Germans spal low profile puller fan.

Learning context

Summer is here and it arrived locked and loaded with triple-digit temperatures. Heat is the second killer of old cars after electrical, and a way to combat the heat is by upgrading to an electric fan to cool the radiator down. Older cars like our E28s are equipped with a clutch fan that is connected to the water pump pulley pulling in fresh air from outside through the radiator and cooling it down. When the clutch fan is not enough the Auxilery fan (or Aux fan for short) will activate at 91C(191°F) on low, and step up to high speed when the temperature reaches 95°C(205F). The clutch/Aux fan combo has been bulletproof in the past 10 years of owning my E28 and have not had any heating issues. Until this year when I took the bronzit beauty out for a drive and the temperature was a little erratic. So I decided to take the leap and install an electric fan.

I spent some time looking at options when it came to what fan to use, how to install it, and how to wire it up to the car. I decided to get a flat blade low profile puller fan for my car, if you want to learn more about the other electric fan options and information check this post I wrote in depth.

Symptoms of a bad cooling system

  • Fluctuating temperature
  • High temp in stop-and-go traffic
  • Blown fan fuse
  • The Aux fan not turning on

Summary

  1. Drain coolant
  2. Remove the clutch fan and fan shroud
  3. Mockup E-fan to the radiator
  4. Remove radiator
  5. Install fan
  6. Create wire harness
  7. Refill coolant system
  8. Parts/Tools

Procedure

  1. Jack your car up to get access to the radiator drain plug, as well as the lower radiator hose clamp. I use the Angry ass jack pads and highly recommend them to anybody that works on these older BMWs.
Angry ass jack pads E28

2. Drain the coolant from your radiator and disconnect the lower radiator hose. I had the coolant drained beforehand as I was working on the heater control valve.

3. Remove the top two screws that hold the fan shroud onto the radiator, and leave it sitting on the radiator as you need to remove the fan clutch to get it completely off.

E28 radiator fan shroud bolts

4. Get your Angry ass clutch fan wrench and holder, when you get them in place turn the wrench clockwise. The fan clutch is reverse-treated onto the engine.

Angry ass clutch fan wrench
E28 fan clutch nut

If I did not explain myself adequately, here is a video of me removing the clutch fan.

5. After removing the fan clutch and shroud, place the top two screws mocking up the electric fan up to the radiator.

INSTALLATION TIP! Check the direction of rotation before installing the fan, don’t want to install a pusher fan as a puller or vice versa.

6. I mocked up the fan centered on the radiator, depending on space and what setup you are going with you might need to off-center the fan on.

I assumed that I would be able to install the fan while the radiator was on the car, but that was not possible and ended up removing the radiator from the car. Unfortunately, I had measured and cut one of the mounting bars, and ended up too short.

7. Disconnect both your fan switches, ATF cooling lines, two radiator bolts, and upper radiator hose to remove the radiator from the car.

8. Once the radiator is out you can lay the fan down and measure what size you need to cut the mounting brackets. I used the top two fan shroud bolt holes to bolt into and had to drill out two holes in the bottom.

8. The fourth bracket I accidentally cut short, I took some of the leftover metal from the E36 heater control valve retro to make a mounting bracket. Once all four brackets are on the radiator, take your grinder and cut the excess from the brackets.

INSTALLATION TIP! If you purchase the Electric fan with no hardware you can fabricate your mounting brackets. Take an M8 bolt and slide it into the slot on the E-fan, take some aluminum flat bar from home depot and you got yourself a bracket. Make a 90° bend to bolt the bar up to the fan, and another hole to bolt up to the radiator.

9. Reinstall the Radiator back onto the vehicle, do not hook the fan temperature switches back on. Make a note for yourself if you have an automatic to add ATF to the transmission to replenish any that was lost.

That is the end of physically installing the E-fan, now we will start on the electrical.

E-fan Wiring Procedure

  1. Before I began wiring the E-fan I spent some time looking for a location to mount the four-pin relay. This is important as you want the relay to be accessible when it comes to troubleshooting the E-fan. I chose to mount the relay below the reservoir using one of the predrilled holes.

2. The four-pin relay is confusing at first but when you look at it and how it works, you will quickly understand it. The picture below shows what each pin is wired to for the E-fan.

3. I advise that you work from the furthest part of the wire harness to get proper measurements of how much cable you need. I started with the fan switch cables, I used some fishing wire to pull the two cables through the heat shrink.

4. For best results run the cables in their permanent route, by working from the furthest part of the harness you can snake the shorter cables into the wire harness efficiently. Use zip ties to secure cables in place while adding cables to the harness.

Installation tip! I found that it is better to only cut a 1/4 slit in the shrink wrap to snake the cables in and out. This way when you heat shrink the cable it will be a better quality job than cutting the shrink wrap completely through.

5. Crimp the pins for the E-fan plug, I ordered a male plug with 14 gauge pins to hook up the E-fan without cutting the connection.

6. This was the first stage of the harness, connections have not been crimped yet and heat shrink has not been shrunken.

7. At the bench I began crimping on pins and heat-shrinking the harness. If you have not crimped pins before, crimper pliers have two crimping sections. One is for insulated pins and the other is for non-insulated, make sure to use the correct section of the crimper.

Installation Tip! if you run into an issue like I did where I did not mark which cable is the signal and which one is the ground for the fan switch signal. Take your volt meter and do a continuity test to find the correct cable. When you have continuity( the same cable) you should get a reading that is less than 1. A reading of .01-1 is what you are looking for, I also went ahead and did a continuity test on all the cables to ensure all the crimps are good.

8. Once the harness was done, I ran the harness along the OEM wiring harness from the 12v battery through the back of the grill and onto the fan switch. To secure the harness I used zip ties and tucked it well to have a clean install.

9. While the vehicle is still in the air, fill your reservoir to the max fill line, turn your temp dial to heat to open up the heater control valve, and start the car to fill the system back up.

10. As the car is running add more coolant to the reservoir and open the bleed screw located on the top of the thermostat housing. Keep an eye on the bleeder screw for when coolant starts to spill out, once that happens close the bleeder screw and keep an eye on the coolant level. Periodically open the bleeder screw to allow air out of the system. Always use BMW blue coolant, I go with a 60% coolant and 40% distilled water mix.

11. Once bubbles no longer come out of the bleeder screw and the coolant does not go below the fill line on the reservoir you have filled the coolant system and can get the vehicle back on the road.

Conclusion

Installing the electric fan was a bit of work and a lot of trial and error, I had to get my E28 back together in a rush as my daily broke down and needed her to get to work. I did not test the electric fan before heading to work, the fan switch failed and I had to hard-wire the fan to keep the car cool. I ordered a replacement fan switch and the fan kicked on, I ended up running two low-speed switches to wire the electric fan and aux fan to work in parallel with each other.

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