Triumphrat

Shunternz · 11-14-2009, 03:10 AM

I have a 2002 Thunderbird. When the engine is a little hot, e.g. on motorway for a while then in slow traffic or cruising the burbs for a while, the overheating dash lamp comes on. The radiator fan does not turn on at this point..nor does it turn on during cool-down.

I disconnected the fan and applied direct power to it. It works OK. Coolant is good – level and colour.

I want to sort this out as I don’t want to have problems come summer.

Any ideas?

Thanks

bradtx · 11-14-2009, 08:10 AM

Shunternz, I don't have a T'bird, but generally a fan circuit also consists of a fuse, a relay and the temperature sensor.

Brad

Shunternz · 11-14-2009, 02:40 PM

Thanks Brad. The wiring diagram shows that the fuse and relay are shared by the shared by the indicator circuit. The indicators work fine So I am assuming that is all ok but may be wrong. Two other things in the circuit are a coolant fan switch and coolant temperature sensor and it could be one of these. Maybe someone out there has had this issue before or can tell me how to test thee things? thanks

rwoodhead · 11-14-2009, 08:15 PM

Just after I bought my '02 TB, there was a service bulletin (and posts on this board somewhere) about a faulty ground that would mis-lite the high-temp light (when the temp was A-OK). It did exactly what yours is doing. It's an easy fix, as I recall, and the bike now has 44K miles on her and still running strong. Maybe that issue wasn't fixed on yours? At any rate, these sure are great, classic bikes.
WOODY

Shunternz · 11-14-2009, 08:29 PM

Thanks Woody. I'll check that out. Agree..a great bike. I really enjoy riding it.

IrlMike · 11-14-2009, 08:40 PM

The fan switch & temp warning light are on separate circuits.

The temp warning light is triggered by a thermistor (variable resistance) sensor, top left of the cylinder head. Haynes manual gives a test reading for it of 255 to 310 ohms at 60 deg C. The sensor can be removed with little or no loss of coolant. A bolt (14mm) or plug of some kind to close the hole would be a good idea whilst the sensor's removed for testing, but as the system is sealed, there's not much chance for air to enter & allow coolant to escape. The sensor resistance is converted by an electronic module, built into the instrument sub loom, to switch the instrument warning light. The sensor or the module could be at fault. A wiring fault in the sensor wire or headlight shell could also cause the light to come on.

The fan can be tested by shorting the fan switch wires. The fan switch is supposed to operate (close) at 99 deg C +/- some unspecified tolerance. (A little high IMO). Could be tested by removing & inserting into boiling water I suppose.

Note these engines run pretty cool whilst the bikes moving, but temp rises a lot in slow/stop-go traffic situations. (Which is why I have a gauge fitted & manual overide switch for the fan.)

Shunternz · 11-15-2009, 11:57 AM

Thanks IrlMike. Very helpful. I'll do some testing and see what's going on.