Temp problem?

Hi all.
My 2003 ST1300A is reading 3 bars on the temp readout all the time.
Even when the engine is cold.
After riding for about an hour it rises to 4 then 5 then flashes 6.
The fans come on and off as normal.
It doesn't seem to be overheating.
The thermostat was replaced awhile ago. Would a wire off the sensor in the thermostat housing cause this?
Is there a different thermostat to bring on the fans?
Any help is welcomed
Thanks
Mark Ireland
:bow1:

Hello Mark, and Welcome!

This sounds familiar ... I'll bet that if you replace the temp sensor, the symptoms will disappear. I was seeing weird light shows on the temp display, and replacing the sensor rectified the problem.

Good luck, and please let us know what you find.

Cheers!
Bill

Hi Bill thanks for your reply,
the item you speak of, is this the part that is located in the thermostat housing or something else?
thanks

OK, wow, this'll be a little tough to explain methinks ...

Page 1-38 of the Honda ST1300 shop manual shows an overhead view of the airbox/throttle body area under the tank. With the tank, airbox, and throttle body array removed, it looks like the ECT (engine coolant temperature) sensor is located on the upper left, front of the engine block.

As I've not actually seen the gizmo myself, I have to say that it appears to be a cylinder-shaped devise, with a hex-head.

Can someone supply a scan of this page, or perhaps a real-life digi-image? I lack the capabilities for both of these right now .....

I hope this info can at least get you pointed down the correct path. Good luck, and please keep in touch; I'll prolly need this info myself some time in the future.

Cheers!
Bill

The ECT sensor is item #22 on this diagram. It bolts into the back of the thermostat housing and if you've ever had the thermostat out, you can see the nose of it poking into the back of the coolant passage.

Checkout procedure (from the service manual):

Turn the ignition off, disconnect the cable from the sensor.

Measure the resistance between the terminals on the sensor that go the the pink and green/orange wires on the connector. Nominal resistance at 68F/20C should be 2.3-2.6 KΩ. I suspect yours is probably showing less than 1 KΩ, which is the range for higher temperatures.

Turn the ignition on and measure the voltage between the pink wire and ground. Nominal voltage should be 4.75-5.25V. If not, look for faulty contacts on the two connectors that connect the wiring harness to the ECM.

Measure the voltage between the pink wire and the green/orange wire. Results should be the same as the last step, check the ECM connectors if not.

HTH.

--Mark

excellent help thanks,
I had my baby apart and suspect it's the sensor.
I have a new one ordered and will keep you posted.
Thanks,
Mark
:

update;
I replace the temp sender unit and took the beast out for a good spin in stop go traffic.
I'm happy to report the reading never once went above 3 bars but was my legs hot lol
Thank you all for replying,
Mark