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Electric Fan Install and Observations


jrhone
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In a thread below I talked a bit about my install, where here is the full blown story.

My car had a strange temp problem...at 80+ MPH the temp creeped up. No matter time of day or outside temp. This started happening just a few months ago. I had a leaky radiator so I swapped that. Prior to all this I had a 71 degree Tstat in the car and it ran pretty cold. I swapped it for a 75 degree and it seemed to run better. Normal temp range was about 2/3 up, never above half. Over 80 it went to 2/3 up the gauge.

I bought Lee's Massive Spal brackets for a 12" pusher fan. I bought a relay, connectors, fuses, and wire and a Spal 195 degree (F) temp switch. I also had The Fan Man build me a pipe that allowed me to put the fan switch outside of the radiator. I wanted the system to be compatible with whatever radiator I had. I drained the fluids and started running wires and wiring the relay. I used the wiring diagram in the FAQ. VERY helpful. Once I got the radiator and out and removed the belt driven fan, I pulled out Lee's brackets and the were a thing of beauty! The fit was PERFECT. He supplied the bolts and I stuck them on the fan, then put the fan in place in the engine bay. I carefully put the radiator in and guided the bolts through the radiator and the fan mounts and tightened them down...then reattached all the hoses. Then I tightened down the temp switch. Plugged it all in and started the car...waited 5 minutes or so (wow it takes the M10 a long time to warm up!). I watched the temp gauge and when it got about 2/3 up I cut it off...hmmm...why is it not turning on? Then I it my manual override switch, still nothing....check fuses, yup the fuse I put in was blown. Replaced it and as soon as I started the car...bam blown fuse. Recheck all wiring, looks good and try a 3rd fuse...bam...instantly blows it. It was a 20 amp...I got the higher performance, higher draw 12" fan with the curved fan blades, so I thought try a 30 amp fuse. Did that and the system worked fine...switch turned the fan on. Then I let it idle until the fan came on...bam came on about 2/3 of the way up, but stayed on. The temp went all the way down to 1/3 of the way up and then lower and then finally cut off. To me thats too wide of a gap. Next day, I made the wires all pretty, mounted my switch in the car and the indicator light. Everything seemed fine, except the fan ran on longer than I wanted...then the radio fuse blew. Hmm...odd. Coincidence? Swapped it. Then again, the radio fuse blew on the way to work...even odder was when I got in the car to go ome the fan kicked on. The car was deal cold. Stopped, swapped the radio fuse again and the fan worked as it should have. I suspect this was because I was using the radio circuit for +12v for the lighted switch. It all worked fine when operation the fan from the switch. When the fan kicked in on its own the 12v came from the fan and went backwards into the switch. (Probably need a diode to make it a one way thing). I unplugged the 12v for the light and tested it out. All worked perfectly and actually, it worked quite well this evening. In a drive through the fan came on just under 2/3 up and ran until 1/3 up then stopped. I was kinda shocked it was only on for maybe 30 seconds. Nice. Then it came on again at a light, and then went off quickly. On the freeway..at 80+ mph....Temp never got above 1/3 up...now why would going to en electric fan help that! The fan was NOT on ever at that speed...so at this point all seems good. My concerns at this point are:

1. Narrowing the range the fan is on.

Right now its acceptable. It gets hotter than i'd like it to while idling...I'd like it to actually come on quicker...

2. The temp of the car normally seems too cold.

I think its running a bit cold. Maybe I need an 80 degree tstat. This will warm the operating temp up a bit to maybe 1/2 up and at that point the tstat will keep it at that temp...my thought on this though is that the fan turn off point is colder than the normal temp of the car so the tstat brings it back down to normal temp which is 176 at the exit of the radiator, and keeps the engine temps about there. The fan goes off at 175 at the entrance to the radiator, which is hotter than 176 at the exit.

Overall seems like a cool way to upgrade he cooling system...its not NEEDED...but I do like it...I'll be going to Arizona next week and the temp this week is 110...so I'll put it to the test!

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I have a few ideas to chuck around.

The stock 'mechanical' fan was mounted to the water pump and would spin all of the time. At highway speeds, the engine (unless you have a 5 speed) might be spinning around 4000rpm. This means that the engine has to work a little harder to keep the, what now is a parasitic load, spinning through the air at such a high speed.

A radiator drops the temperature of the coolant across it by a certain amount.. some are 30*, some are 50*.A good way to think about the cooling system is to look at how the radiator acts under different circumstances.

With a mechanical fan, there are two 'modes'. One while the airflow through the radiator is less than what the fan provides and one where it is more. The cooling ability of the radiator will be better in the latter.

With an electrical fan, there are also two 'modes'; fan off and fan on. (I know that you can factor is speed and get 4 or 8 or 32 different instances, but simple is better) Again, the cooling ability of the radiator is better in the latter, but worse in the former.

What an electric fan does is improve the car's ability to cool itself when it needs it AND remove any parasitic losses for when it doesn't.

What are you using for a temperature controller / trigger?

If you get into the $100 range for temperature controllers, you can buy ones that have a variable fan speed that corresponds with the amount of cooling that is required.

Time to go to temple,

Jay

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In a thread below I talked a bit about my install, where here is the full blown story.

My car had a strange temp problem...at 80+ MPH the temp creeped up. No matter time of day or outside temp. This started happening just a few months ago. I had a leaky radiator so I swapped that. Prior to all this I had a 71 degree Tstat in the car and it ran pretty cold. I swapped it for a 75 degree and it seemed to run better. Normal temp range was about 2/3 up, never above half. Over 80 it went to 2/3 up the gauge.

What is condition/age of water pump?

I bought Lee's Massive Spal brackets for a 12" pusher fan. I bought a relay, connectors, fuses, and wire and a Spal 195 degree (F) temp switch. I also had The Fan Man build me a pipe that allowed me to put the fan switch outside of the radiator. I wanted the system to be compatible with whatever radiator I had. I drained the fluids and started running wires and wiring the relay. I used the wiring diagram in the FAQ. VERY helpful. Once I got the radiator and out and removed the belt driven fan, I pulled out Lee's brackets and the were a thing of beauty! The fit was PERFECT. He supplied the bolts and I stuck them on the fan, then put the fan in place in the engine bay. I carefully put the radiator in and guided the bolts through the radiator and the fan mounts and tightened them down...then reattached all the hoses. Then I tightened down the temp switch. Plugged it all in and started the car...waited 5 minutes or so (wow it takes the M10 a long time to warm up!). I watched the temp gauge and when it got about 2/3 up I cut it off...hmmm...why is it not turning on? Then I it my manual override switch, still nothing....check fuses, yup the fuse I put in was blown. Replaced it and as soon as I started the car...bam blown fuse. Recheck all wiring, looks good and try a 3rd fuse...bam...instantly blows it. It was a 20 amp...I got the higher performance, higher draw 12" fan with the curved fan blades, so I thought try a 30 amp fuse. Did that and the system worked fine...switch turned the fan on. Then I let it idle until the fan came on...bam came on about 2/3 of the way up, but stayed on. The temp went all the way down to 1/3 of the way up and then lower and then finally cut off. To me thats too wide of a gap. Next day, I made the wires all pretty, mounted my switch in the car and the indicator light. Everything seemed fine, except the fan ran on longer than I wanted...then the radio fuse blew. Hmm...odd. Coincidence? Swapped it. Then again, the radio fuse blew on the way to work...even odder was when I got in the car to go ome the fan kicked on. The car was deal cold. Stopped, swapped the radio fuse again and the fan worked as it should have. I suspect this was because I was using the radio circuit for +12v for the lighted switch. It all worked fine when operation the fan from the switch. When the fan kicked in on its own the 12v came from the fan and went backwards into the switch. (Probably need a diode to make it a one way thing). I unplugged the 12v for the light and tested it out. All worked perfectly and actually, it worked quite well this evening. In a drive through the fan came on just under 2/3 up and ran until 1/3 up then stopped. I was kinda shocked it was only on for maybe 30 seconds. Nice. Then it came on again at a light, and then went off quickly. On the freeway..at 80+ mph....Temp never got above 1/3 up...now why would going to en electric fan help that! The fan was NOT on ever at that speed...so at this point all seems good. My concerns at this point are:

If this is indeed your step by step, you missed Burping the system. search for process of burping.

1. Narrowing the range the fan is on.

Right now its acceptable. It gets hotter than i'd like it to while idling...I'd like it to actually come on quicker...

To nip this whole thing in the bud, Just flick the switch as needed.

2. The temp of the car normally seems too cold.

Stay with the 75tstat for your climate.

I think its running a bit cold. Maybe I need an 80 degree tstat. This will warm the operating temp up a bit to maybe 1/2 up and at that point the tstat will keep it at that temp...my thought on this though is that the fan turn off point is colder than the normal temp of the car so the tstat brings it back down to normal temp which is 176 at the exit of the radiator, and keeps the engine temps about there. The fan goes off at 175 at the entrance to the radiator, which is hotter than 176 at the exit.

i dont understand what you are saying here,

check this link for cooling operation

http://bimmers.com/02/

then faq/spec engine > cooling > operation

Overall seems like a cool way to upgrade he cooling system...its not NEEDED...but I do like it...I'll be going to Arizona next week and the temp this week is 110...so I'll put it to the test!

Stay cool!

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Man I am no expert but I have an opinion. It seems the faster you go in one of our cars the greater the wind resistance and the greater the load on the motor. Load will create much more heat at 4000 rpm than no load at 4000 rpm. These cars were originally designed to operate in more moderate temps, so place like AZ, TX, CA they are probably maxed at top ambient temp. Add that to the resistance of the wind at higher speeds. Equals getting hotter and hotter. For example, hang you hand out the window in second gear at 4000 rpm...not much resistance. Now hang you hand out the window in 4th gear at 4000 rpm and you will see what I mean.

In the end when you get hot at idle its an airflow issue, when you get hotter and you run faster it is a capacity issue....water is not staying in the radiator long enough to cool. Next summer I am looking into a pusher fan and a radiator with an additional row. Right now i run a 320i Rad. I think the Rads from the M3 will work with mods

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As someone aluded to, the sensitivity/accuracy of the temperature probe will determine how accurately the fan cycles on/off.

This is typically a 'thermister' - a resistor who's voltage varies with temperature. Once the voltage is sufficient to trigger the fan motor relay, the fan starts.

I'd be very concerned about arbitrarily adding a 30Amp fuse to the stock 30 y.o. wiring. Before I did that, I'd wire it independently using 14 ga. wire minimum. No point in having an under-hood fire if you can avoid it.

Cheers!

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You said you bought a pusher fan, What side of the rad did you put it on? Motor side or grill side?

30 amps seams like a lot of fuse for a fan, What is recommended?

Where is your temp sensor actually mounted? The radiator varies in temp from location a lot.

Still, temp creep at 80+ is not unheard ofand as long as you stay out of the red.....

John

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I don't have an electric fan, but just an FYI, I had my radiator recored with a 3 row a few years ago and my temp gauge has never gone above half way! Still running the stock fan. Food for thought.

BTW, I live in the Phoenix area and regularly see temps in excess of 110 degrees during the summer. And my car is a daily driver!

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I don't have an electric fan, but just an FYI, I had my radiator recored with a 3 row a few years ago and my temp gauge has never gone above half way! Still running the stock fan. Food for thought.

BTW, I live in the Phoenix area and regularly see temps in excess of 110 degrees during the summer. And my car is a daily driver!

Man thats perfect. All the mystery about these cars is no mystery. They are radiated for milder temps, so to compensate we need to just increase capacity some. This allows the fluid to stay in the rad longer...what did your recore run?

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I have a 12" pusher as well and it is controlled by the Megasquirt computer. The temp sensor is in the top radiator hose, close to what you have, so I set the computer to turn the fan on at 210 and off at 200. The bottom of the radiator will be around 30 degrees cooler than that so with my 80C thermostat it works great. My fan has only turned on once the entire summer, when I got stuck in some traffic. In normal traffic it never turns on.

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I don't have an electric fan, but just an FYI, I had my radiator recored with a 3 row a few years ago and my temp gauge has never gone above half way! Still running the stock fan. Food for thought.

BTW, I live in the Phoenix area and regularly see temps in excess of 110 degrees during the summer. And my car is a daily driver!

Cool! I will probably go to a 3 core radiator as well. It will be overkill but it'll never be too robust.

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I don't have an electric fan, but just an FYI, I had my radiator recored with a 3 row a few years ago and my temp gauge has never gone above half way! Still running the stock fan. Food for thought.

BTW, I live in the Phoenix area and regularly see temps in excess of 110 degrees during the summer. And my car is a daily driver!

Cool! I will probably go to a 3 core radiator as well. It will be overkill but it'll never be too robust.

Actually a 3 core is not too robust for our climates. Now, up North were it is usually in the 90's for summer...well those guys may not really need 3 cores. But us folks down south an in the deserts. Yep we need them. Someone get making nice aluminum 3 cores and I will buy one

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picture-1.jpg

This arrangement is not proper. You need some compliance in the hose to compensate for the engne back and forth movement. With the above set-up, you are literally pushing on the radiator and core support each time you brake.

If you need to fit a second sensor, I suggest using a twin branch manifold from another car. I don't remember from which car to source one, but I suggest looking at e21, Tii and M10- 318i.

As for the radiator, I suggest unsing an aluminum-core e21 radiator.

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I'll be in Laguna Beach tomorrow and Monday, on business (we have an office in Irvine, on Von Korman, across from John Wayne). If you're around, I'd like to see your setup, since as you may know from other threads, I'm redoing everything in Otis's electric and cooling system.

If you'll be around, and if you don't mind me dropping by, can you email me at david dot bowen at gt dot com? Thanks!

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