TOPIC:

Hi guys
have a problem with the cooling system on my A1, it has been laid up for about 6 months waiting for me to get around to working on it but when i took it off the road the system was working fine, having got it fired up yesterday it has become apparent that the fan is coming on too late[at first i didn't think it was coming on at all]it eventually comes on just before the needle goes into the hot section, before being laid up it came on just past the middle of the gauge i am thinking temp sensor but any idea why it would suddenly do this
thanks
Paul

Hey

is the sensor free of corrosion ? Just try to clean and check if the result is the same .

regards

Holger

Your fan switch is a simple mechanical switch. I would suggest the switch just failed and it just happened at the point of layup. It could also be the fan relay. Either one are susceptible to failure from age. You can test the relay by bridging the terminals in the relay coming from the cooling switch and seeing if the fan comes on.

Here's a 3 minute video on the operation/testing of a cooling fan switch.



It demonstrates a simple test. It could be that the "contacts" in the switch have arced to the point that the resistance acroos the contacts is too great. Probably time to replace the switch. you may want to take the opportunity to find a switch that closes 210F instead of the typical 200-230F switch.

Thanks for the info Kawboy could low coolant level have anything to do with this problem, also is the temp sensor the one on the front of the engine on the left side as you sit on the bike
thanks
Paul

The temp sensor is on the top of the cylinder head just left of the upper rad hose.

Page 61 of the service manual

The fan switch is on the top of the cylinder head just right of the upper rad hose with a 2 wire connector. that's the connector you want to jump to test your fan relay. When the coolant gets too hot, the fan switch is made, so you can just jumper the connector and the fan should come on.

Also on page 61 of the manual.

If the coolant is low or really low and the sensor in the thermostat is not submerged in coolant then likely the fan switch and the water temp sensor are also not submerged in coolant and all kinds of shit will happen. then the question is why is the coolant low?

Another possibility is that the Temp gauge is reading off, this can happen for a variety of reasons. If you have or can borrow an IR thermometer you can see how hot the engine is really getting.

Air can also be a problem, quite a few people on this site have had issues bleeding air out the cooling system on 1300's. If your reservoir level got low, or you opened up the radiator cap, it's possible you have an air bubble. I had one that really caused some strange problems with the cooling fan on my bike. But if the level is full and you haven't messed with it then is most likely an electrical issue.