Why is it never simple? :(

[guest18]

Been using the MZ for the last couple of days and all was right with the world, bike running well, all electrics working, heated grips lovely.
Half an hour/an hour after getting home tonight I hear the fans running outside... so I nip out and they are just stopping, I check the rad/engine and it's nice and cool. Ten/twenty minutes later they're going again.. so I have pulled teh fuse until I can get time to have a look 
Why me??! 

[Richard]

Fans, on an MZ ?  What is the world coming too.  They will be using unnecessary water cooling on bike engines next !

Richard

[Richard]

1.  Check the thermostat.  Known to stick and the fans are designed to come on to cool the engine after being switched off I believe - as with most cars now.

2.  Buy a 2 stroke, air cooled MZ.

Richard

[guest18]

Fans, on an MZ ?  What is the world coming too.  They will be using unnecessary water cooling on bike engines next !

Richard

Necessary to pass the noise regs... despite the bus sitting next to you making more noise than the second coming and spewing out enough particulates to clog a dustbin 

Sticky thermostat shouldn't make the fan cut in when it's been parked for a while surely? Especially in this cold weather... it had been ridden for about 20 miles, probably 15 of that dual carriageway / motorway and seemed fine when parked up (no fans or indication of being overly hot).

I was wondering if it might be a bad connection at the temperature sender switch (for the fans) or a failure of that part  Especially with the loom having been moved around quite a lot recently... that or salty rain/road water getting into the plug. Either way, I'll have a dig and I'm sure it will prove to be simple (I hope!  )
As to suggestion 2.
No!

I have too much scrap parked around here without adding to it 

[guest146]

If your happy its not hot remove the wires from the fan swtch. If it then stops its is the control switch if not you have a wiring problem unless of course it computer controled.

Ken

[bullet350]

 if i remember about 7 years back when i had one, the thermo switch is on top of the l'h radiator.

bullet350

[guest18]

Thanks for the pointers chaps, hissing down with rain tonight so I think that will be a job for Saturday in the daylight and I'll sneak out in the car tomorrow 

[guest18]

Finally  I managed to get out and have a look at it tonight.
Findings so far:

With the bike stone cold the fans run as soon as the fuse is put in.
Conclusion- Not a physical overheating problem, must be electrical, prime suspect the temp switch

With the Switch disconnected the fans stop.
Conclusion - The switch is switching and it's not a random other short(?)

The switch has continuity across the terminals.
Conclusion - I wish I had a manual(!) No conclusion possible.

Both switch poles have continuity to ground.
Conclusion - Makes sense!

The wires to the switch from the loom have near battery voltage
Conclusion - nothing firm but leads me to suspect the temp switch should have high resistance when cold and continuity when hot.

So..... I reckon the switch is U/S and needs replacement, or am I missing something obvious? Anyone disagree?! 

[002]

I agree...Switch US !!!!


Jethro

[themoudie]

I agree...Switch US !!!!


Jethro

Concour and you have the info. 

Toodle pip, Bill

Aye Jethro, Healthy New Year 'Old Fruit'!

[002]

Ah Fruit !   Thought you said Fart !

Well correct on both counts 

And Hoping you Have a Healthy New Year too !


Jethro

[guest40]

Why is it never simple?  Cos ,thats why, cos it is!

^%$*& Honda!  fixed the radiator now it wont run! The electronics cut out a couple of seconds after ign switched on, F$#@!


OOOPS a rant...

Honest I didn't mean it, It just sorta slipped out, like by accident.

[guest18]

£39.57 for a temp switch 

I'm going for a stiff drink and a lie down lads, I may be some time...

[Mark]

£39.57 for a temp switch 

I'm going for a stiff drink and a lie down lads, I may be some time...

Can't you stick a manual switch on until you find a good used one.

[guest40]

Smudge, when I replaced the fans with a larger single unit I also wired in a manual overide switch (illuminated). Whenever the fan comes on the switch lights up. This is handy as when one is belting down the highway and frinstance there is a coolant leak, when the temp reaches "fan on" there is a visual signal much earlier than the near invisible in sunlight standard idiot light that tells you that you have just overheated and cooked the engine. The overide switch can be activated if there is a failure in the temp switch and the original idiot light comes on cos of overheating.

The Honda Scoot which got cooked due to a radiator puncture is causing me much trouble at the moment. I will be putting in a LED for the fan on the dash. One doesn't always hear the fan/fans while in motion and the early warning gives you time to assess whether it should be on and why it is on.
 All this may sound a bit anal, but with regular ambient temps of over 35 C it is important to take every advantage possible