Author Topic: Cooling Fan Activation Time Interval (Read 26211 times)

kris · « **on:** March 31, 2015, 07:56:46 AM »

From a cold start at 32 degrees F/ 0 C how long would one reasonably expect to wait for the cooling fan to activate (at idle)? It is my final concern after re-assembly of the bike. The rad flows perfectly, the thermostat activates properly, the fan was bench tested and was fine. So, from what I've read, there is a temp sensor that can go bad and the relay in the fuse box. All connections are fine and have been treated with Deoxit. I'm amazed at the fine condition of the 29 year old connections.

Any thoughts?

Thanks!

The Mighty Gryphon · « **Reply #1 on:** March 31, 2015, 08:20:10 AM »

I never timed it, but I would guess between 5 and 10 minutes.

Do you have temp gauge on your bike? That would let you keep an eye on things.

kris · « **Reply #2 on:** March 31, 2015, 08:25:12 AM »

Hey Jim,
I wish I had a gauge. I guess it was the era of "idiot lights" when they built this one. She has run for 15 minutes, at least, and no fan. No temp warning light either....so it has me a little concerned.

Thank you

Elipten · « **Reply #3 on:** March 31, 2015, 08:26:02 AM »

Maybe more, mine take a bit of time even in 80F temps. Never timed it.

The Mighty Gryphon · « **Reply #4 on:** March 31, 2015, 08:35:42 AM »

That does sound a little long even considering how cold our garages are right now. Can't help you with this as I've never had to go into that part of the bike. I am thinking you need to find the connector for the sensor and do some resistance checks to see if it is responding to the rising temperature. Then, there is a temperature relay in the electrical box that turns on the fan and the idiot light.

Now that you read the above you know everything I know.

kris · « **Reply #5 on:** March 31, 2015, 08:53:34 AM »

Thanks Jim. I'll re-visit the connections, jiggle 'em a bit and say a prayer. It's worked so far!!

RobP · « **Reply #6 on:** March 31, 2015, 09:59:47 PM »

I need to test this, too. The Haynes manual says the only way to test the temp sensor is to swap it out.

In the box 'o parts I received from the PO there was some sort of cheap aftermarket fan and a spare temp sensor relay. I surmise he might've had issues here, too.

kris · « **Reply #7 on:** March 31, 2015, 10:17:07 PM »

Thanks RobP. I'd be curious to know if it is a common problem with this cooling system. If not I may be worrying about nothing simply since the fan didn't activate and I, clearly, don't want to do any damage to this fine machine. I will let it run a little longer and see how it goes. I have read other threads about fans that malfunctioned and people riding them without a problem so long as the bike was moving and had reasonable airflow through the radiator.

The Mighty Gryphon · « **Reply #8 on:** March 31, 2015, 10:48:26 PM »

Kris, can you reach in and spin the fan blades freely? Did you check the motor and brushes when you had things apart? Does your bike have a temperature gauge?

Over the winter I installed a temperature gauge and a manual fan override switch on both K's. I plan on using them to keep things cool in the summer rather than waiting for the engine to go to the melting point to turn on the fan.

Have you tried another fan test at idle? You might want to put a fan on the exhaust headers and the cylinder head before running for any extended time in the garage. On my bikes those guys get pretty hot without any airflow over them.

kris · « **Reply #9 on:** March 31, 2015, 10:49:59 PM »

Robert, you're amazing. Thank you. Pardon my ignorance but how exactly do I run these tests? How am I grounding/ jumping these circuits?

The Mighty Gryphon · « **Reply #10 on:** March 31, 2015, 10:52:20 PM »

Quote from: rbm on March 31, 2015, 10:42:59 PM

Cooling circuit:

If you want an override switch to turn on the fan when you desire, wire up a SPST switch to Pin E and ground the other side of the switch. When riding, flip the switch and the fan will start. Overtemp light on the dash indicates the override is in use.

That's what I did on my bike. Works nicely.

Ground pin E will simulate overheating to the temp relay. The fan should start and the overtemp light illuminate. Proves the temperature relay is functional.

Jumper A2 to 45 will bypass the temp relay and the fan should start. Proves the fan works.

Jumper A3 to ground and the overtemp light should illuminate. Proves the warning light functions.

If you want an override switch to turn on the fan when you desire, wire up a SPST switch to Pin E and ground the other side of the switch. When riding, flip the switch and the fan will start. Overtemp light on the dash indicates the override is in use.

rbm · « **Reply #11 on:** March 31, 2015, 10:58:15 PM »

Identify the temperature relay in the relay box:

The relay socket is normally held in with one screw, that when removed, allows the relay to be extracted from the relay box. Hold it upside down and probe with the jumpers on the exposed connectors. Power up the bike and make sure the kill switch is in the middle. Be certain about the pin markings as the diagram shows the orientation from above.

kris · « **Reply #12 on:** March 31, 2015, 11:02:01 PM »

Cheers!

kris · « **Reply #13 on:** April 02, 2015, 10:28:33 PM »

Robert,
I got the temp light to illuminate but could not get the fan to go. I blew two fuses in the attempt. Not sure I was doing it correctly. Am I simply running a grounded wire to the contacts on the relay? And you mention hitting the 45 but my relay looks like your b/w photo...it says 15 and 31 so I'm not sure how I would go about jumping all of that.

In any event I ran the bike for 20 minutes at idle speed plus a few throttle twists. The exterior temperature was about 45 to 50 degrees F. I don't get a good feeling about the fan not coming on after that period of time. What do you think?

Thanks,
Chris

rbm · « **Reply #14 on:** April 02, 2015, 10:49:08 PM »

Pin 45 and 15 represent the same pin but different designations obviously. Pin 31 is ground. From the schematic, jump 15 to A2 with a wire. That will apply +12V dorectly to the fan. If the fan fails to spin up, it needs servicing and most likely replacement.

kris · « **Reply #15 on:** April 03, 2015, 07:31:46 AM »

Thanks Robert

rbm · « **Reply #16 on:** April 03, 2015, 08:42:18 AM »

If you want to perform JUST that one test (jumpering 15 to A2), remove the relay from the socket and jumper the exposed connectors. It's easier to perform and saves the relay from potential harm.

Oh, I didn't read deep enough into your other post. You may have been doing the second test wrong, causing the blown fuses. You're not supposed to ground the relay contacts 15 or A2. Just take a wire and temporarily join those two contacts. That second test simulates the overtemperature contacts closing, sending current to the fan.

beemrdon · « **Reply #17 on:** April 03, 2015, 04:43:37 PM »

Hi Kris,
Why not find/buy a temp guage and install in place of the idiot light?

good luck with it.

kris · « **Reply #18 on:** April 04, 2015, 06:15:31 AM »

Thanks Don. I would like to keep the machine stock and I can be a stickler for repairing/ making sure that the original system is operating as it should. A gauge is always a good idea and it's a little surprising that BMW, given the expense and loftiness of these bikes, didn't throw a gauge into the mix. This bike doesn't have a fuel gauge either. Old school, I guess. I appreciate your note. I'll soldier on and get it done! Most important thing is to get her on the road and, as Johnny would say, whack 'er!

The Mighty Gryphon · « **Reply #19 on:** April 04, 2015, 08:47:57 AM »

You should install a manual fan switch, especially if you will be getting caught in any traffic in the summer. It's a pretty easy job.

Get a used hazard flasher switch or any standard spst switch and wire so that it connects pin E of the temperature relay to ground.

Easiest way is to use a posi tap on the purple and green wire that connects to the relay for one wire to the switch. The other wire will go to the ground point on the frame backbone under the tank. The switch can go into one of the open spots on the switch pad under the instrument cluster.

You don't really need a temperature gauge around here as long as you have a fan switch and turn it on when you hit heavy traffic. BMW cleverly designed their engine so that it is difficult to use anything other than their highly overpriced gauge and sending unit. I know it can be done, and maybe someone here can explain how. Otherwise, figure on $100+ to install a used temperature gauge.

Snowman · « **Reply #20 on:** April 04, 2015, 12:08:16 PM »

+1 on the manual switch. It was 28F in my garage this morning and I timed my bike at 17 minutes until the fan came on. My temp guage was at 2/3 towards the red. I know when it was colder my fan would take much longer to kick in when just idling, I would have to give it some throttle for a few minutes before the fan came on.

TimTyler · « **Reply #21 on:** April 04, 2015, 01:11:52 PM »

At 32F I wouldn't be surprised if the fan didn't come on at idle.

Turn the fast idle / choke switch to "high" and let the bike idle at 2krpm. The fan should come on within ten minutes or so.

rbm · « **Reply #22 on:** April 04, 2015, 03:16:53 PM »

Quote from: The Mighty Gryphon on April 04, 2015, 08:47:57 AM

... BMW cleverly designed their engine so that it is difficult to use anything other than their highly overpriced gauge and sending unit. I know it can be done, and maybe someone here can explain how. Otherwise, figure on $100+ to install a used temperature gauge.

BMW cleverly designed their highly overpriced gauge to work with their highly overpriced sender. It should be possible to find matched aftermarket sensor / gauge sets that can be adapted to the K-bike. The important part is the sensor - to make sure that it has the correct M10 x 1,0 thread size to replace the drain plug on the oil/water pump. The gauge can be anything, digital or analogue, that can be made to fit on the dash (52mm). I believe the BMW gauge has a specially designed scale that is expanded for the range of interest. An analogue aftermarket gauge may not have this feature.

The Mighty Gryphon · « **Reply #23 on:** April 04, 2015, 10:14:08 PM »

They also designed the water pump so that only their cleverly designed sender would work. The OEM sender is very short having no extension beyond the threaded portion. Every aftermarket gauge has a sender with an extension that will obstruct flow from the pump and probably bottom on the opposite wall of the water passage.

Because of the goofy transfer function of the OEM sender you can't use it with an aftermarket gauge. Unless you want to find another location for the sender, you are stuck with the cleverly designed and stupidly expensive gauge.

I have considered tapping the hole for 1/8" NPT female thread and putting in a close nipple and coupling to accept the extra length of a standard sender. Decided not to take a chance on something that wasn't easily reversed. Also didn't like having the sender sticking out another 3/4" down there.

kris · « **Reply #24 on:** April 04, 2015, 11:05:59 PM »

Enlightening as always, gentlemen. Thank you. Tim, your comment is interesting. She sat at 1,000 rpm idling away very evenly. Sounded great. As I mentioned earlier it could be that I'm chasing a ghost. I have no reason to believe any component is faulty. I just find it odd that after 20 minutes the cooling fan didn't come on. My Concours (much smaller rad and, perhaps, much smaller engine mass, would probably come on in under 10 minutes.

Jim, the price of the sensor does seem brutal. Try it in Canadian dollars these days...plus 28 per cent. Ouch.

Would anyone be able to hazard a guess as to the point, length of time-wise, at which I am starting to cook the engine? Or will she give me an audible warning first?

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Author Topic: Cooling Fan Activation Time Interval (Read 26211 times)