Howdy Krew


My fan used to come on all the time. 

A few months ago I completely flushed the cooling system several time using a cleaning product. 

I also fitted a nice 3 bar radiator.

Ever since then the fan has not come on. At first I assumed it was a result of the cooling system working a lot better. But it wont turn on even when the bike is left to idle for 10-15 mins.

- The fan will come on fine when I jump the appropriate wire in the relay socket.
- the temp warning light comes on when the appropriate wires are jumped in the relay socket.
- the fan does not come on when the temp sensor wires are jumped
- There is continuity between the temp sensor and the FI computer and the relay socket
- it will not start when I ground the E wire in the relay socket (with the temp sensor unplugged)
- It will not start when I ground the temp sensor wire
- checked resistance at relay socket when hot and cold and got expected readings 

So based on all that, the fan is fine, the wiring is fine, the temp sensor is fine....which leaves the relay. I should have 2 spares but can not find them anywhere. A new one is $160 AUD (F%$k!!!)

Is it possible to test the relay? it looks fine on the inside and the contacts are not fused shut.

Am I missing anything else?¿?¿

Try to ground "E" with the relay present in the socket, if the fan don't start you need a new relay.
I'm assuming that you have checked that you have power on 9 and ground on 31.

Is there a coil that closes the fan contacts?  Is there continuity through the coil, or is it opened?  I am not familiar with that relay, but those are the first questions that come to my mind having read what has been checked so far.

Thanks Inge.

No go. looks like ill need a new relay

Anyone got one?

You've got nothing to loose by opening the relay and carefully examining the circuit card.  What you are looking for is cracked or cold solder joints.  I had the same problem as you one time on my K100.  I found a cracked joint on the circuit card and, using my soldering iron, I reheated the joint to re-melt the solder.  It brought the relay back to life.  If I remember correctly, the cracked joint was on one of the contact tabs.  Use a powerful light and magnifying glass to be certain you have looked over everything carefully.

get smithys Floyd

then send me yours for examination ????

Thanks Robmac

Examined in the sun with a 30x mag. glass and my untrained eyes cant see anything out of the ordinary.



Cheers Charlie, Ill PM smithy and post you my unit

bugger. double bugger in fact.....

It seems that both my relay and temp sensor are buggered. 

smithy was kind enough to post me a known working relay.....

The idle test with the new relay installed resulted in nothing....no fan

I then performed the following test:
_________________________________________________________________________________
earth the wire on pin E as you know. but you need the sensor and relay all connected and place a bridging wire on pin E to earth. Then you need to start the engine, when you press the start button you should here the fan come on.
If fan comes on the problem is with the sensor.
If no fan, the problem is with the relay.
This test needs to be done with the engine running, not just ignition on, or you wont get a result.
_________________________________________________________________________________

with the E pin earthed and the engine running, the fan came on. (It did not come on with the old relay installed, confirming the old one was buggered)

So, the new relay is fine....but my temp sensor is shite.

This is weird because it gives the correct ohm readings at the female relay socket when the engine is hot and cold......

floyd wrote:So, the new relay is fine....but my temp sensor is shite.

This is weird because it gives the correct ohm readings at the female relay socket when the engine is hot and cold......

This doesn't quite make sense, have you let the engine idle long enough?
The fan should start at ~175 ohm......

What Clymer suggests is far out, what you then do is connecting the fan
relay and Jetronic unit together.
I would guess this have been written a Monday morning, and they have
mistaken the temp sensor for a thermo switch.

Floyd if you earth the wire from the sensor that goes to pin E of the relay with the engine running the fan should start, and does as you've mentioned. So that discounts the relay as the problem.
The sensor could be shagged, or may not be making a good earth.
Make sure you get the bike up to operating temperature, then let it idle for a while to see if the fan comes on.
If fan still doesn't come on I would suggest that the sensor is rooted.

I remember that Charlie did have bad ground connection on his sensor some
time back......this will also affect engine running.
But as you say that you read normal values when the engine is hot and cold
is confirming that the ground connection is OK.

sounds very confusing Floyd

just as a query ...does the light in the dash - instruments come on when the fan is working ?  if not ..could this be a clue ?


the second thing to check is that the body of the temp sensor  to the main earth point  does not read high ...or anything more than an ohm ....at anytime

third and last thing to ask ...is your thermostat in the radiator working properly ....do you see it cease rising in normal conditions at about 90 odd degrees c ...( talking about the additional instruments temp gauge ) apologies if you don't have one and I forgot .

cheers and good luck

Inge...you are bloody right....as usual!


Earlier, I let it idle for 15 mins - no fan. I didnt want to let it sit idling for longer then that....based on all reports it normally comes on after about 10mins....

simthy suggested I go for a decent ride first to get it up to temp, so I went for a rather spirited ride up and down the Galstone gorge

Yum Yum! (Google Map)

Then let it idle in the shed....and what do ya know? on comes the fan...

Thanks all!

woohooo !!!

Another happy K rider!

Good result Floyd.

good on you Floyd , top result.
nice spot down there on the Berowra waterfront. Did you stop for a coffee or were you pumped to get back and check the sensor.
you should be fine for the Eden ride now.

groverK wrote:good on you Floyd , top result.
nice spot down there on the Berowra waterfront. Did you stop for a coffee or were you pumped to get back and check the sensor.
you should be fine for the Eden ride now.

Nah the Galstone gorge road is just a bit south of the Berowra waters one. Both stunning though, and the Berowra one has the added adventure of the ferry crossing at the bottom and a cafe or 2, as you say

Its a great loop from where im staying to head east through the Galstone gorge and then come back via Berowra waters. 

Big advantage of the place im 'crashing' at the moment (Dural). There are some great roads right on my door step. The 2 mentioned above, the Old Pacific Hwy, Wisemans Ferry etc etc.

Looking forward to Eden. Have been loving life on the road, and these solid walls and ceiling are starting to give me claustrophobia

Back to the fan though....Great to know its working again....but wow the difference in cooling since I cleaned the system and also fitted the 3 core radiator is remarkable. Earlier, the fan would come on very regularly. Now it seems it takes a lot longer. Although not much testing so far, so we'll see. 

I wonder what killed my relay, as it was working fine, and internally it looks ok to me. Ill send it to Charlie the electro guru kuru for his investigation.