Bongo Fury

Sorry sorry sorry I've searched and remain confused (not unusual). Driving up mountains in North Wales last weekend the dash temperature gauge (Mason alarmed) almost reached the danger zone, so I shut down facing the wind in a lay by. All hoses were hot. None of the fans had come on, so we wired one of them direct to the battery to get home (I have learnt to carry lots of tools and odds and sods in this car....
At home, I've run some radflush through the system for about an hour until the coolant was quite hot, about one o clock; drained the coolant from rear and front heaters and rad (pretty clear, no sludge); once it has cooled I flushed it through from each til I got clear water. Removed the 2 pin temperature sensor from the side of the block and propped it up in a can of water on the hob: as temperature rises the resistance alters.
Has anyone got the inclination to tell me what to check next?

Thanks for this suggestion. I can't see a relay in the lush projects diagram http://lushprojects.com/bongopartsmk2/c ... o=.html#10 , but the fans each have 4 connectors so something is going on. A mate of mine will look at the wiring with me soon...

It'll be one of these http://lushprojects.com/bongopartsmk2/c ... mgno=.html relays then... I'll have to look very closely!

These are links to drawings of the sensors and relays but no real identifiers to which relays do what, and also to two schematic diagrams, but they aren't like any I've ever seen before!

http://lushprojects.com/bongopartsmk2/c ... 1of03.html

http://lushprojects.com/bongopartsmk2/c ... mgno=.html

http://lushprojects.com/bongopartsmk2/c ... 2of03.html

http://lushprojects.com/bongopartsmk2/c ... 3of03.html

Be careful, Bongo cooling fan system is a lot more complex its dual speed and controlled directly by the ECU diagram aas always on-line as below;

Thanks very much, that could help.
I found a lot of verdigris in both pins of the connection block which is almost central at the top of the radiator, perhaps that was the problem? Testing will have to wait til my mate has helped me bleed the system now.
Does anyone know what resistance I should get at the sensor when cold and at operating (?) Temperature?

Yes its in the manual, which is at home, where I won't be for a while longer! It might be here on the forum but a search for "thermistor resistance" didn't come up with the actual resistance range as such. Ah ha found it viewtopic.php?p=613280#p613280

Thank you very much Geoff! Could save me a lot of time getting scalded and re-bleeding.

I measured a new genuine temp sensor and got the following readings
Temp Resistance
18.8 2500
21.5 2380
23.4 2240
27.4 2080
30 1880
32.4 1710
37 1480
41.1 1300
44.3 1190
47.6 1063
51.5 945
54.8 836
59.5 732
63.4 655
67.8 545
76.2 481
80.3 413
87.4 338
88.9 304
91.6 280
96.5 247
98.2 232
99.8 210
100.5 195

Very many thanks both. This device works as it should. The plastic was so loose in the base that I expected it to be shot, sealed it with araldite and then ordered another one anyway! Ah well, it's a spare...

The fans come on very last minute, i.e. at a buttock clenching high temperature.
I tested mine by removing the plug from the two wire temp sensor and inserting a variable resistor to pick up the trigger point for the fans coming on. These were my results - please treat as approx.

Open circuit: Both fans high speed (fail safe mode?)
330 ohms: No fan (did not test for the boundary between open circuit and high resistance)
around 177 ohms - both fans normal speed
around 149 ohms - both fans high speed

Scarily, but perhaps predictably, the temp at which the fans come on is off the temp/resistance scale posted above which as the test could not go above 100 deg C.
Perhaps somebody could do the temp/resistance test using jam or something that can be raised above 100C