Author Topic: Overheat light on, fan not starting  (Read 836 times)

Offline Laitch

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Re: Overheat light on, fan not starting
« Reply #25 on: October 29, 2024, 05:30:28 PM »
I am not the biggest brick fan fan.
Eat more chocolate, bananas, pizza, and sausage; drink more beer and exercise less. Keep at it and you'll get there eventually—maybe the biggest fan fan ever!  112350  You'll need to upgrade to stronger suspension springs front and rear.
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Offline Mavebrick

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Re: Overheat light on, fan not starting
« Reply #26 on: October 30, 2024, 01:29:05 AM »
Thank you folks. Will keep y’all posted on my progress (or lack of) periodically.
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  • 1986 BMW K75C

Offline Kaos

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Re: Overheat light on, fan not starting
« Reply #27 on: October 30, 2024, 02:12:23 AM »
Eat more chocolate, bananas, pizza, and sausage; drink more beer and exercise less. Keep at it and you'll get there eventually—maybe the biggest fan fan ever!  112350  You'll need to upgrade to stronger suspension springs front and rear.

 :laughing4-giggles:
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Offline Mavebrick

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Re: Overheat light on, fan not starting
« Reply #28 on: November 04, 2024, 10:58:20 AM »
I bought an aftermarket 12V, 80 watt fan. Seems like it pulls 6ish amps. Is that going to be a problem connected to the line the factory fan was on or is it better suited for a separate
Line connected to the battery directly with a switch and fuse?
  • Houston Texas
  • 1986 BMW K75C

Offline Laitch

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Re: Overheat light on, fan not starting
« Reply #29 on: November 04, 2024, 01:00:13 PM »
Hopefully your choice of fan doesn't consume excessive current to start up. The problem could more likely be with the rate of air per minute moved by the fan. The output of the Spal 6.5" puller replacement fan is 350 cubic feet per minute. It seems to be a successful replacement. I haven't found the cfm rate of the original equipment fan. Which fan did you buy; can you post a photo of it?

The fan needs to be wired into the temperature sensing switch circuit to run the engine optimally. A battery switch option can lead to overheating from not operating the fan enough, to poor engine performance from operating the fan too much. The engine can be forgiving of inept operation but not indefinitely tolerant.  :laughing4-giggles:
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline Mavebrick

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Re: Overheat light on, fan not starting
« Reply #30 on: November 04, 2024, 01:39:59 PM »
Hi Laitch i got a generic radiator fan that fits. Being in Hellton i mean Houston texas i was leaning towards the overkill fan option to keep things cool in summer which is 8months a year. Might have overdone it? Seems like this fan does 1000cfm with 6.67amp draw. I got no clue about the startup draw.
  • Houston Texas
  • 1986 BMW K75C

Offline frankenduck

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Re: Overheat light on, fan not starting
« Reply #31 on: November 04, 2024, 02:05:11 PM »
If you're worried about putting too much current through the thermo relay then you could power your uber fan with a relay triggered by the VIO/YEL wire that usually powers the fan.

Relay wiring:

85 - Ground
86 - VIO/YEL wire to original fan
30 - In-line fuse to battery
87 - Power out to new fan
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Offline Laitch

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Re: Overheat light on, fan not starting
« Reply #32 on: November 04, 2024, 02:21:50 PM »
As I indicated, your choice of fan is likely to be ok; don't sweat it— :laughing4-giggles: — but frankenduck often has valid workarounds that can help calm the waters concerning outcomes.

The fan will start and stop as necessary—no problem. Don't let that bother you either, that usually means the system is either working appropriately, or there's isn't enough coolant in the system. The main thing is to have clean radiator fins with relatively fresh coolant in the radiator and expansion tank, and refill the system according to BMW's instructions. I change coolant every couple of years but long life coolant is promoted to last around five years.

The fuel tank can get hot to the touch. You can always add a fuel cooler that could decrease the fuel temperature a little. There are a few threads here concerning that. Verify you have insulation under the floor of the tank—stuff like Reflectix that can be purchased at Home Depot. There is a document concerning heat management on the site and even more threads concerning insulation to mitigate temperature swings. MartinW, a member here that lives in a paradisical hell below the equator—has taken several successful steps to cool things down.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline Kaos

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Re: Overheat light on, fan not starting
« Reply #33 on: November 04, 2024, 03:34:10 PM »
I bought an aftermarket 12V, 80 watt fan. Seems like it pulls 6ish amps. Is that going to be a problem connected to the line the factory fan was on or is it better suited for a separate
Line connected to the battery directly with a switch and fuse?

That should be the same as THE OEM fan, and about 6.6amps. With a 7.5 amp fuse in place you should be solid if it doesnt abnormally drain when starting up.
Looks like a solid replacement. You could directly connect it to the OEM connector with these specs without having the joy of messing with the relay.

If you havent filled up the coolant yet you could still test it with the sensor in hot water and see if it starts and when it starts, it doesnt pop your fuse.
if i remember correctly it should be starting up at 90 celcius (194F )

I do strongly recommend testing it.
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Offline Mavebrick

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Re: Overheat light on, fan not starting
« Reply #34 on: November 05, 2024, 09:22:34 PM »
Okay just opened my eyes more and looked and am discovering more potential gremlins. What are these disconnected electrical connectors? I have no idea what they do and why there were disconnected by one of the many previous owners. Please advise, thank you. Mainly am thinking it is going to affect the fan functionality via temperature sensor.
  • Houston Texas
  • 1986 BMW K75C

Offline frankenduck

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Re: Overheat light on, fan not starting
« Reply #35 on: November 05, 2024, 09:25:34 PM »
The second one looks like the hazard switch connector. Non-issue.

If you identify the wire colors to each connector it makes it much easier for us to help you.
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Offline Mavebrick

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Re: Overheat light on, fan not starting
« Reply #36 on: November 05, 2024, 10:34:55 PM »
Apologize for the poor lighting. First picture is brown and green wire. Second picture is blue/white, yellow/purple and brown wires.
  • Houston Texas
  • 1986 BMW K75C

Offline Laitch

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Re: Overheat light on, fan not starting
« Reply #37 on: November 05, 2024, 11:59:12 PM »
  • Along the Ridley in Vermont.
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Offline Mavebrick

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Re: Overheat light on, fan not starting
« Reply #38 on: November 06, 2024, 01:15:15 AM »
Thanks Laitch that helps a lot. Looks like i can wire the fan with a switch to the heated grip connector for a manual switch. Will that work? Put the positive of the fan to the green/black with a switch in between and the negative of fan to the brown wire which I am assuming is ground? Seems like fuse 1 is 7.5amp so it could work? I don’t see a specific heated handlebar switch in instrument cluster. Am i missing something?
  • Houston Texas
  • 1986 BMW K75C

Offline Laitch

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Re: Overheat light on, fan not starting
« Reply #39 on: November 06, 2024, 07:46:30 AM »
The method depicted in this post and the ones after it seems to be the most accepted way to wire up a fan switch. If I wanted a switch, I'd follow a successful method rather than sweat it.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline Laitch

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Re: Overheat light on, fan not starting
« Reply #40 on: November 06, 2024, 08:28:16 AM »
I don’t see a specific heated handlebar switch in instrument cluster. Am i missing something?
You're missing heated handlebar grips; they're an option at extra cost. No switch is supplied because your Brick apparently didn't have heated grips at original purchase.
  • Along the Ridley in Vermont.
  • 1995 K75 89,000 miles

Offline Mavebrick

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Re: Overheat light on, fan not starting
« Reply #41 on: November 06, 2024, 09:59:18 AM »
Thank you for the link Laitch. I think I am going to wire the manual switch and fan directly to the battery with an inline fuse. Seems like the easiest thing for me to do.
  • Houston Texas
  • 1986 BMW K75C