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Online Art

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Radiator fan not coming on
« on: 17 March, 2020, 06:17:01 PM »
Radiator fan failed to come on, cooling system over heats, thermostat housing cap venting steam and de-pressurising the cooling system, steam bellowing out from under the fuel tank.

Fuse tested OK
Fan spins up on jump leads
Fan relay tested OK
Thermostat housing cap tested OK
All connections and wiring are clean and good

Let's try that again. Fired it up and there she blows, five minutes or so of idling and the fans doing nothing, the thermostat cap pops and steam bellowing out from under the fuel tank. When this happens in the confines of the garage it looks far worse than when out on the city streets. This needs to be sorted here we go...

ECT sensor removed and tested OK
Thermostat removed and tested OK
Water pump impeller checked OK
System flushed no blockages

Re-filled with fresh coolant, it was due anyway, left it ticking over for around five minutes and just as the radiator top hose becomes too hot to the touch the fan kicks. It can only be something I touched, prime suspect being a loose connection, I'd just like to know what. Not sure why I was testing the thermostat or checking the water pump but there it is a definitive listing of how to troubleshoot a failed radiator fan and then some without a conclusion.

Gremlins  :087:



Offline ToonCBF

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Re: Radiator fan not coming on
« Reply #1 on: 18 March, 2020, 09:50:13 AM »
I had the very same problem on my Biffer, turned out to be a fractured wire that sometimes gave a connection and sometimes didn't.

Honda dealer replaced thermostat, sensor, housing, and just about everything they could, tested it and it was fine, on my first ride in town it boiled up and dumped its coolant! I took it back to Honda and they went through it all again and found a slight fracture in the positive feed. Not had an issue since!!

HATE BLOODY WIRING!!!!!

Toon
I have the body of an 18 year old...... I keep it in the freezer!!!! (Spike Milligan)

Online Art

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Re: Radiator fan not coming on
« Reply #2 on: 18 March, 2020, 12:25:22 PM »
Interesting. In testing the fan, its relay and the ECT sensor I disturbed a few wires. Been out and about this morning and it seems fine no over heating but no sitting idling either so I guess there was no need for the fan to come on, time will tell.

If it fails again I now have a prime suspect, thank you.

In the meantime I've been toying with the idea of fitting a water temperature gauge in the engine hose leading up into the thermostat housing (and a voltmeter to keep an eye on the 14.2v at 5,000 RPM stator output) these look interesting.

https://www.ebay.co.uk/itm/Car-Radiator-26-40mm-Water-Temp-Temperature-Joint-Pipe-Sensor-Gauge-Hose-Adapter/153790051951?var=453820797791

https://www.ebay.co.uk/itm/Universal-Motorcycle-Digital-Thermometer-Water-Temp-Temperature-Gauge-Red-LED-UK/303362398668?hash=item46a1ced9cc:g:NFgAAOSwEC9dzS9F

https://www.ebay.co.uk/itm/Battery-Monitor-12V-DC-LED-Digital-VoltMeter-Gauge-Voltage-Marine-Caravan-Car-UK/333538081978

Offline phild

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Re: Radiator fan not coming on
« Reply #3 on: 18 March, 2020, 03:17:51 PM »
I had the same problem on my wife’s CBF600SA.

Sometimes the fan kicked in, but most of the time it didn’t. Back to the dealers a few times, Sod’s law worked every time. Boiled over in Dijon and Bordeaux.

After going out of warranty, spent over £200 on coolant change, thermostat change etc, finally got told it’s going to cost a load to change the fan etc.

I said, ‘What about the relay’?.......’They never go wrong’.........ordered one myself (£12 I think) 20 minute job, 4 years problem free.

Intermittent fault in the relay.

Offline jm2

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Re: Radiator fan not coming on
« Reply #4 on: 18 March, 2020, 04:31:26 PM »
I was going say; sound like a sticky relay (well, contacts more than armature).

- First use for a while ??  could be a symptom of relay trouble.  Swap it for the main beam ahead of another scolding.

Has "someone" swapped a relay to prove another, in the past ?
Only do it right - no bodging please.   Keeper of the failed stator list.   John.

Online Art

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Re: Radiator fan not coming on
« Reply #5 on: 18 March, 2020, 06:21:24 PM »
Struth, I spent most of Saturday leisurely inspecting, testing and checking this, that and the other. I shudder to think what spares a dealer would have palmed me off with. I think they replace parts willy nilly because its the lesser of the two evils parts costs vs labour costs.

The bikes been in regular use, 5,000+ miles over winter, yet there may be something in the sticky relay theory because I rarely ride in city motor traffic. Therefore the engine rarely gets a chance to reach a temperature where the fan would come on.

When I tested the relay I gave it several jolts of 12v across the coil and it was working fine and gave a strong buzz every time, maybe that gave a sticky relay a new lease of life?

Two prime suspects now, a dodgy wire and/or a dodgy relay.

Well so far and so good we're back on Happy Days.
« Last Edit: 18 March, 2020, 06:23:51 PM by Art »

Offline iNCORRIGIBLE

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Re: Radiator fan not coming on
« Reply #6 on: 18 March, 2020, 06:42:50 PM »
Hi,Art.Found from experience that an impressive click within that relay does not always mean reliable & useable continuity at the contacts supplying the cooling fan! I test by energising the relay while observing the contact resistance at the closed contacts;can often be variable & intermittent to say the best.Tends to improve the more you pulse it just to lead you astray( they all have a soul you know & can be very devious). Sub a like relay in for comparison or splash out 12 Sovs!.Ed :125:

Online Art

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Re: Radiator fan not coming on
« Reply #7 on: 19 March, 2020, 09:39:42 AM »
I wish I had now Ed. When testing the relay I simple jumped it with 12v and tested the continuity with a multimeter buzzer. When phild posted with the intermittent relay fault theory it occurred to me testing the resistance would have been a better idea. Equally with ToonCBF's damaged wiring theory testing for voltage drop may have been better too.

Thanks all your ideas have been noted in the servicing schedule for future reference.

 


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