Official Electric Fan wiring thread!

[JamesE30]

Fan wont work unless I tap the relay... ??

Hey guys, need some help with a strange problem,
I have wired up my new 16" SPAL Pusher exactly as described by Klug.
I have all new wiring (12GA), a new 82* single speed fan switch, and new relay as pictured below.

With the thermo switch activated (or bypassed) The fan will only turn on if i physically TAP the relay.. with my finger..
Just a light tap does it, but if i don't touch it nothing will happen.
Here is a quick vid showing what I mean.

https://www.youtube.com/watch?v=oTann85ZvhI&feature=youtu.be

I have tried this with 2 brand new relays and they do the exact same thing. The whole system/switch/fan works perfectly, but the fan wont turn on until i tap the relay.. I'm baffled?? Any ideas?

This thread has been super helpful so far so thanks to everyone who contributed!

[Heitzke]

Just finished mine up, thread was very helpful. Spal 16" pusher on a M42 radiator.

I ended up wiring mine differently, but with the same components as everyone else. Forgive my picture of a screen (lol) but this is what I did:



I didn't end up tapping power for the rocker switch, so I just don't have a light on it. Generally, using the rocker switch and/or the temp switch to act as the ground for the circuit.

[MattPro]

Chiming in here with my modified electric fan setup.

Short story: I followed this DIY on how hook directly to the Aux fan wiring with a 80C switch. Easy to do, simple and not a lot of electrical cabling. I was running a SPAL 16'' Puller as my primary cooling fan for a few months.

This worked like a charm- except under the ONE scenario: If the temp switch kicks on the fan at 80C and starts cooling, and I was ready to park or turn off the car and the fan was still on- the fan would obviously lose power. IF I had to turn the car back on for whatever reason (maybe to move the car after you parked it) and the temp was still over 80C- the startup of the ignition I would blow the stock 30A aux fan fuse every time. I found out that this can happen when switching from the +12v of the battery (ignition ON but engine OFF) to the new +14.3v you get from turning over the engine and obtaining the power bump from running from the Alternator. By the way- I never blew the in-line fuse I added from the +12v of the fan- only the 30A fuse in the fusebox.

Also- which is a great point on why I modified it- was that say you are getting ready to pull into your destination, you might be idling a bit to find parking etc etc and the car gets up to 80C. The fan kicks on and might still be running when you turn the car off. Which is fine. But if you need to turn the car back on again, the thermo switch on the thermostat- which goes to the DME- will tell the DME that the engine coolant is too hot and don't supply fuel. So you get this hesitation when trying to start up. I can't get a definite temperature of what the thermostat DME switch reads that tells the engine that it is too hot. I only found out what resistance it reads at certain temps. If you know- I would really be interested what this threshold is.

I know this post has good intentions, but there is definitely some misinformation in here.

For starters, the DME will not "cut fuel" because the coolant is too hot when starting. The temp switch on the radiator is only used to control the high/low speed relays, not fed back to the DME. The DME reads the temp from the temp sender in the thermostat housing. If you are having hesitation during hot starts this sensor is probably bad, and the DME is reading that the engine is colder than it actually is so it is enriching the mixture to compensate for a cold start causing hesitation.

Secondly, when the engine starts cranking and the alternator starts putting out 14v this shouldn't cause you to blow a fuse. It is probably because you were trying to start the fan on high speed on the low speed circuit. When the fan first starts its current draw will spike, and if too low of a fuse is used it will blow. Maybe when your fan automatically turned on when driving it was already spinning so it didn't draw as much current, but the change to 14v definitely would not blow a fuse, otherwise everytime your fan kicked in while the car was running at 14v the fuse would blow.

[grinchxvx]

For those who have their cars on the 80/88c what would cause the high speed to not kick in? I have it wired pretty similarly but j use the snowflake button just because in the winter it gets so cold that I may not need the fan on at all but I can't tell if it's kicking onto high mode or not.


Sent from my iPhone using Tapatalk

[Mark 42]

I know it's an old question, but...

The only thing I can think of is that the trigger voltage/current is almost, but not quite enough to activate the relay.

Hey guys, need some help with a strange problem,
I have wired up my new 16" SPAL Pusher exactly as described by Klug.
I have all new wiring (12GA), a new 82* single speed fan switch, and new relay as pictured below.

With the thermo switch activated (or bypassed) The fan will only turn on if i physically TAP the relay.. with my finger..
Just a light tap does it, but if i don't touch it nothing will happen.
Here is a quick vid showing what I mean.

https://www.youtube.com/watch?v=oTann85ZvhI&feature=youtu.be

I have tried this with 2 brand new relays and they do the exact same thing. The whole system/switch/fan works perfectly, but the fan wont turn on until i tap the relay.. I'm baffled?? Any ideas?

This thread has been super helpful so far so thanks to everyone who contributed!

[jeenyus]

I tried to simplify this whole process by replacing the AUX fan with the new electric puller fan. I then wired it exactly how the AUX fan is setup, albeit removed the resistor prior to the AUX fan and replaced the 15a fuse in slot 4 with a 30a fuse.

The fan works only when i push the snowflake, but i was really hoping it would turn on when the car reached 80C, like the new AUX switch i purchased. Any idea why it wouldn't kick on automatically when it reaches temp?

Thanks.

[rustneversleeps]

well reading all this gives me a little insight on how about getting the fan to work thanks god for the Bentley manual it should be pretty easy to trouble shoot..need to be sticky thread..

for the above comment check relay K6 which is the high speed..

[rustneversleeps]

Ok got my low speed Bosch resistor but it's the wrong one..
The one that i have in the car is the hard wire one Magna would it be ok to use the the Bosch resistor instead of the Magna...

[bradmer]

Back to the first page bump

Because it's not stickied, yet.
This thread is great, can confirm it comes on a tick below half. Had originally run a toggle switch for manual operation and opted for this instead. Below quoted from OP, thank you Dave.

1: Install fan in car. To Preface a GOOD WORKING factory fan will out cool most aftermarket ones. I run stock fans in almost all the swap cars i do here as they move ALOT of air.
- I should have gotten the the radiator and pusher from the donor car for the swap, it would have been cheaper, factory and less mental anguish.

2: Find stock fan wiring on drivers side under drivers headlight - (BEFORE the plug)

chassis BK/Blue to black on fan

chassis brown to blue on fan

BK/Green did not use.

- Sorry to beat a dead horse man, but when it comes to auto electric I need to be lead straight to it. Noobs. :)

[phenryiv1]

My 2.7i swap came with the mechanical fan deleted so I went with an electric fan. I had it running off of a thermostatic controller (temp probe in radiator) with a relay. Unfortunately, the controllers have a reputation for failing, which is what happened to me. The circuit board had continuity issues and the board kept losing power but I never knew if it did or did not have power because hearing the fan run with the engine running was impossible.

So last week I realized that the controller had shit the bed…mostly because I saw the temps shoot into the red and the car pissed coolant from a blown coolant passage. Fortunately the head gasket did not go- the gasket at the TB heater failed first (thank God).

Now I am trying to build a new fan controller based on the 61-31-1-364-272-82 switch in the A/C fan port in the body of the radiator. Plan is to use either one or two 5-pin relays. I can either use a 2-relay system that has an override switch in parallel with the thermostat switch on a single-relay setup OR I can run 2 totally separate parallel relays – one thermostatically controlled and one manually controlled. A single will be easier to wire up but a double relay system has the benefit of redundancy.



Obviously the 30/51 will be fed with a fused 12V+ signal and terminal 85 will be grounded. Terminal 87 will feed the fan when triggered. The assistance comes in two areas: The use of the 87a terminal and setting up “indicator” or “status” lights associated with 87 & 87a.

So the new setup will use an 80*C switch trigger that goes into the A/C port in the radiator. It will supply the trigger to the 86 terminal on the relay. I can also run a simple toggle switch in parallel to the terminal 86 or I can run the second relay. Which would you recommend- two relays with discrete triggers or dual triggers run in parallel to a single relay?

Second question focuses on an indicator or status light. I would like to have a light that remains on when the relay is powered but not triggered by wiring the status light into the 87a terminal and then having it change color or illuminate when the relay is triggered and the 87 terminal fires. Ideally the “triggered” light would be tied across the coils of the fan but that would be too hard to wire up so this is a good (enough) indicator solution. I found something like these:

http://www.alliedelec.com/sloanled-255-12-r-g/70015146/

http://www.dialight.com/Product/Details/557_led_panel_mount_indicators_PMI/5571432203F

If I tie one color into the 87a to show power to the relay and the other color into the 87 terminal to show that the relay has been triggered, that should at least give me an idea of the status of the relay (though obviously not the actual fan), correct? And would that small LED require any sort of diode or resistor? It would be the only thing on the 87a terminal when the relay is not triggered but when wired in parallel with the high-draw accessory fan will it cause issues?

While this all makes sense to me in theory I just don’t understand circuits well enough to have full confidence in the schematic that I drew up in my head.

[mjweimer]

phenryiv1 - I like where you are heading with this and will be watching for updates. I would like to wire up my swap with this same scheme.

Please update this thread when you sort it out!


MJ

[She loved E]

Can anyone who used Klug's method help me out? I'm trying to figure out the best place to hook into +12 (always on) and acc in the engine bay. Klug said to hook into the accessory fuse box (little black box next to main fuse box), BUT, I don't have one of those. :( My car is an 89 325is but its been modified pretty heavily by previous owners. Will be poring over wiring diagrams to see if those wires are still under the hood but in the meantime would appreciate any tips.

[She loved E]

Cancel that, figured it out yesterday. On my car +12 is red, acc is green. My small fuse box is missing but those two wires were there. All hooked up & tested. Fan works great! Thanks to everyone who contributed to this thread - esp Klug for the detailed parts list & diagram.

[TimeMachinE30]

What are factory fan options for an M30 swap if not using a Spal?

[digger]

What's the best way to get the stock aux fan to run on high with A/C button pressed?
I want the low and high to work as per normal when a/c is not on albeit with 80/88 switch