Temp guage & mystery sender?
Discussion
Coolant temp guage hasnt worked properly since the 100 amp fuse went 3 weeks ago.
When i turn the ignition key the needle moves a couple of mm but wont register any temperature. checked the obvious connections under the bonnet. Had this last year too but it came back to life - sender maybe?
ALso i have another sender without any percievable connection mounted slightly forward of the plenum near the dizzy, looks like a water temp sender but its never been connected, anyone got any ideas? It has a post type connection (not spade)
When i turn the ignition key the needle moves a couple of mm but wont register any temperature. checked the obvious connections under the bonnet. Had this last year too but it came back to life - sender maybe?
ALso i have another sender without any percievable connection mounted slightly forward of the plenum near the dizzy, looks like a water temp sender but its never been connected, anyone got any ideas? It has a post type connection (not spade)
Have you done any electrical tests? I'm sure they aren't all the same, but it seems common for the gauge to send a voltage to the sender, which earths it through a variable resistance (thermister). If your sender has got a single electrical terminal it is almost certainly this sort. If it has two terminals it may be, if one of the wires is an earth.
With this sort, with the wire disconnected at the sender, you should be able to measure a voltage on the wire when the ignition is on and you should see the gauge go to one end stop (probably cold). I would be wary of shorting the wire, but if you earth it through a low resistance such as a couple of hundred Ohms you should find the gauge goes to the other end of its travel. This shows the gauge, power supply and wiring are OK. If not, you need to start narrowing down which of these is at fault.
The other check worth doing is to measure the resistance of the sender itself. It will probably be in the region of 5kOhm cold and go down as the temperature rises.
With this sort, with the wire disconnected at the sender, you should be able to measure a voltage on the wire when the ignition is on and you should see the gauge go to one end stop (probably cold). I would be wary of shorting the wire, but if you earth it through a low resistance such as a couple of hundred Ohms you should find the gauge goes to the other end of its travel. This shows the gauge, power supply and wiring are OK. If not, you need to start narrowing down which of these is at fault.
The other check worth doing is to measure the resistance of the sender itself. It will probably be in the region of 5kOhm cold and go down as the temperature rises.
The sender unit is a spare from the engines range rover days, it can be used as a replacement but will need calibrating with a resistor preferably a variable one, if you
Do a search on this forum you will come up with some details about it, the replacement sender will work better than the original that due to its location suffers from being inaccurate in the winter due to air flow .
Phil
Do a search on this forum you will come up with some details about it, the replacement sender will work better than the original that due to its location suffers from being inaccurate in the winter due to air flow .
Phil
GreenV8S said:
If your sender has got a single electrical terminal it is almost certainly this sort. If it has two terminals it may be, if one of the wires is an earth.
Its the single terminal type (one spade) The sender itself is located forward of the 'spare one' between the plenum and dizzy, you need a small hand to get at the blighter - wheres Jeremy Beadle when you need him?
Will do a test on the wire with ignition on. Cooling all appears normal, a bit un-nerving with no guage on hot sumer days though.
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