Temp question

[Africatwin]

Evening all.

Newly acquired van again so just fault finding at the moment, first issue I’ve got is the temp sensor. The light comes on and goes off as normal, needle stays at the bottom when ignition is on, once the engine starts it rises really quickly then disappears,
I don’t believe it’s over heating. Coolant looks “ok” so I took a reading from the block and expansion tank. It’s ready between 90 and 95… would this potentially be a faulty sensor?

[Aidan]

temp gauge works with inverse relationship to resistance, so going hot it's finding low resistance at the switch or wiring fault between sensor and gauge

test resistance of sensor, cold should be in the 100s of ohms range, if it is low or open to ground (ie no resistance) then sensor has failed

if sensor resistance seems okay then continuity check the wiring

could be the 14 pin connection to the dash circuit board so worth taking a look at this for stability of connection and damage to board whilst doing the continuity checks

[ZsZ]

There is a topic on the US forums Thesamba about testing the gauge itself with 3 pieces of 100 ohm resistors.

There are two different temp sensors for the petrol vans (one for gauge, other for ECU) they are not interchangeable as they have different resistance values.
Your gauge might be connected to the wrong one.

E D I T:
Links:

https://www.thesamba.com/vw/forum/viewt ... p?t=464113

https://www.thesamba.com/vw/forum/viewt ... p?t=633048