Mont 4RT Burning out cooling fan motors ? Why

[JustinC]

Hello All,

2011 4RT 4 months into my ownership had burnt out a fan motor (and in the process melting the central boss of the plastic fan itself).

I got a new fan motor (and plastic fan blade) fit them both (spinning freely and running as it should seemingly) but after approx 15 hours riding later the new fan motor has... burnt out melting the fan centre again!

Surely this cant just be bad luck can it?

Why might that happen twice ? Its not catching - so I doubt thats the problem. So far as I could tell the fan would run perhaps 5 mins after a cold start and would run and stop periodically as needed.

Might it be a relay or voltage regulator thing.

Any thoughts gratefully received before I order new motor and fan ...again!

thanks

[misscrabstick]

Too many volts are frying it to death, get a voltmeter connect between two wires that feed fan, check with engine running, anymore than 13.5 maybe 14 volts will kill the fan, my money is on a faulty voltage regulator unit, which is a very Honda thing to happen.

 

[JustinC]

Thanks a lot Miss !

at the moment have the rad off. To check volts to fan, I guess I’d need to run it until hot enough for the temp sensor to power the fan supply (which I can do- would have to let it get hot with no rad on) or would the whole bike voltage be the same - and hence would there be an easier Vorlage supply to check whilst it’s running ?

it doesn’t have lights BTW (just thinking about other easy to get to electrics)

 

[jonnyc21]

You should be able to bypass the temp sensor to cause the fan circuit to engage and test... There is a good chance that your regulator is not working correctly and you are getting high voltage to everything. 

Edited February 26, 2021 by jonnyc21

[jimmyl]

Is the fan free when the radiator gets warm ?

Does  the fan sound to be running fast or varying with engine speed 

[JustinC]

Thanks all three.

the fan was running steadily and was free to turn (I would occasionally do so by hand to check it) even when engine warm. I had it noticed it varying with engine speed.

basically on one ride today it failed and the engine overheated - I hadn’t noticed the fan wasn’t running today so the first I knew was the coolant boiled over (and of course I stopped it to let it cool).

but until today, it ran normally.

jonny, where is the temp sensor and how do I override it? If that’s tricky, maybe it’s easier to check voltage on the downside of the regulator somewhere?

[jonnyc21]

3 hours ago, JustinC said:

Thanks all three.

the fan was running steadily and was free to turn (I would occasionally do so by hand to check it) even when engine warm. I had it noticed it varying with engine speed.

basically on one ride today it failed and the engine overheated - I hadn’t noticed the fan wasn’t running today so the first I knew was the coolant boiled over (and of course I stopped it to let it cool).

but until today, it ran normally.

jonny, where is the temp sensor and how do I override it? If that’s tricky, maybe it’s easier to check voltage on the downside of the regulator somewhere?

Should be on the side of the radiator on the shifter side of the bike if I am remembering correctly.  if you do a continuity check on it I want to say you will find an open circuit if that is the case then to by pass it and check voltage all you have to do would be to pull the wire off the plug and put a jumper between the connectors. and then check the voltage at the fan wires. 

Also, yes you can check down line closer to the regulator and should be able to tell if your having an issue there.  If voltage is fine you might just have a bad fan motor? 

[JustinC]

Thanks a lot. I’ll give it a go today.

[jimmyl]

I seem to recall that the temp sender is not just a switch but one that gives varying output as the temp rises - the ecu decides when the fan comes on. I think the Ecu uses the temp info for fuel setting and limo home modes etc

could be wrong but sure I read it it somewhere 

Maybe need to check before just linking out 

[sportsawyer]

6 hours ago, jimmyl said:

I seem to recall that the temp sender is not just a switch but one that gives varying output as the temp rises - the ecu decides when the fan comes on. I think the Ecu uses the temp info for fuel setting and limp home modes etc ...

Jimmyl is correct. It's a thermistor that has room temperature resistance of 2.3 – 2.6 kΩ. And it's used by the ECU for FI adjustments as well as telling the fan relay to start. I can't see blocking it out. And if the ECU sees the resistance is out-of-range it may put the bike in limp mode. I know if it's simply disconnected, the bike will go into limp mode.

I'd suspect your problem is due to a stopped fan blade. It's happened to me once when a pebble got into the fan housing and jammed the blade. The fan motor kept trying and melted the fan blade around its metal hub.

Another time I had the fan stopped because the "purse lock" (what it's called in the parts manual, see Frame F-21 Reference #11) that holds the wire / vent gas hose bundle together a couple inches above the ignition coil had rotated so it stopped the fan blade. I found that soon enough that nothing was damaged. This could be intermittent.

These problems were probably seen by others because the fan housing was changed in 2016 to open it up in the bottom (where I had a trapped pebble) to reduce chance of a jam there, and raise the height on the sides so the "purse lock" or wires can't move into the fan blade sweep.

If a previous owner took the gas vent hose out of the bundle, and your bike has the "purse lock", it may fit loosely and can rotate into the fan sweep, then rotate out of the way later. Check that first.

[JustinC]

Well, I temporarily installed (without fan fitted) and filled the rad with water so the temp sensor sensing, unpackaged the voltage regulator bundle, ran the bike, removed the fan relay, bypassed it and measured voltage at the fan supply to find it reading 6.6v.

 What does that mean?

[JustinC]

The fan motor is toasted - more or less siezed. When connect it to the running bike (with relay bypassed) the bike idle dips under the load and wires get hot (I pulled the bypass wire out and it burnt my little pinkies  )

[oz thumper]

HI Justin, I have not had this problem running 4RT's since 2005 so I can't speak from experience. However high current draw is usually what burns out electrical appliances. This occurs from excessive load on the unit,or LOW voltage.

Low feed voltage increases the current draw (amps) . High voltage does not. Really high voltage can arc through the insulation or cause damage to electronics but not burn out wiring or motor windings.

So don't agree that 14V will cause the fan motor to melt.

Good luck

 

[JustinC]

I’m measuring 6 volts at the fan motor supply with engine at idle. (I expected it to be high but it’s low voltage).

Presumably a regulator problem ?

are there any other likely causes of low system volts (BTW - earth contacts cleaned)

I didnt realise Oz thumper that low voltage supply might burn the fan motor out as well as high voltage. thanks for that

Edited February 28, 2021 by JustinC
didnt make sense

[JustinC]

I ran through the electrics check as per back of the Maintenance mannual.

The resistances all seem to check out OK (Primary coil, Temp sensor, ground checks etc  all ‘above and below’ the wiring harness (ie the harness checks are satis).

The only real ‘finding’ is that the manual spec for the resistance checks between the three yellow stator wires (each against the others) and in fact the impulse generator  wires (red and green) are 0.5-1 Ohm (at 20deg C) whilst when I checked them I was getting 1.5 Ohm approx (all of them consistent) but the day temp is perhaps 8 degrees. Not sure if the temp would explain the difference.

Im hoping the explaination is (as Miss said!) a faulty regulator so Ill fit a new one (along with fan motor and fan) and see what volts I get. If still too low - perhaps call the stator into question.