940 Celebration temp gauge

[940volvoman]

Hi,

As stated above,the temperature gauge on my 940 Celebration,has packed up.

Where should I start looking,at the sender,perhaps?I don't know where it is though,and whether it can be tested.

No doubt I'm not the first to have this problem,so I'm hoping for some guidance.

TIA.

[360beast]

The sender is under the inlet manifold threaded in to the cylinder head. It is under port #2 of the inlet manifold and has a D shape plug, you can test it with a multimeter on the ohm/resistance setting, put one probe on a sensor pin and one on the alternator body and see what the resistance value is, do the same for the other pin and let us know the values.

I'm sure unused the alternator body last time as the earth but you may need to use the block or somewhere else.

[Forrest]

If you unplug the cable from the sender and short the two wires together in the plug the gauge should shoot to maximum when you turn the ignition to position 2. A kinder way to test it is to use a suitable resistor to mimic a correctly functioning sender. Either way, this should prove or disprove the wiring and instrument.

If the above points towards the sender it might be worth checking the thermostat before you try replacing the sender. The sender is difficult to get out and if it is tight you have to break off the electrical connection in order to get a socket over it. If the thermostat has failed open it can prevent the coolant reaching normal temperature and hence the gauge could in fact still be working.

[940volvoman]

Thanks,so far.What I have noticed is that when I turn the key to start the key,the gauge 'twitches',but thats it.


Anyway,I'll try what's been suggested and report back.

[Laird Scooby]

Originally Posted by 940volvoman

Thanks,so far.What I have noticed is that when I turn the key to start the key,the gauge 'twitches',but thats it.


Anyway,I'll try what's been suggested and report back.

That suggests the PCB on the back of the instrument cluster. Try the tests as described above and see what you've got first though.

[940volvoman]

There are two senders,side by side.I expect the temp gauge sender is the one nearest the firewall,not the one at the front of the engine.
Can someone confirm this?

Thanks

[Laird Scooby]

Originally Posted by 940volvoman

There are two senders,side by side.I expect the temp gauge sender is the one nearest the firewall,not the one at the front of the engine.
Can someone confirm this?

Thanks

No, because it's not! Look :

Originally Posted by 360beast

The sender is under the inlet manifold threaded in to the cylinder head. It is under port #2 of the inlet manifold and has a D shape plug,

The fuel ECU uses the one under #3 inlet tract and is closer to the bulkhead. Use a 100 Ohm resistor to protect the guage, push it into the connector with one wire per pin and switch the ignition on. The temp guage snsor is a 2-wire animal with neither connected to earth, unlike the CTS (Coolant Temperature Sensor) which is also a 2-wire animal but both sensors internally are linked to earth via the body of the sensor. The CTS has a connector similar to the fuel injectors so you should be able to differentiate between the two fairly easily.

[940volvoman]

Thanks,Dave.
I just had another look,and you are,of course right.It is the front D shaped connector.
The problem I will have for testing is the lack of the 100ohm resistor.(or any resistor for that matter.

I'll order one in go from there..

Thanks again....

[Laird Scooby]

Originally Posted by 940volvoman

Thanks,Dave.
I just had another look,and you are,of course right.It is the front D shaped connector.
The problem I will have for testing is the lack of the 100ohm resistor.(or any resistor for that matter.

I'll order one in go from there..

Thanks again....

You could use a paper clip or similar short length of wire and flick the ignition on and as soon as you see the guage move or not, switch off again but you'd need to be quick.

[940volvoman]

Since posting my temp gauge problem I haven't had time to follow up.
However it doesn't mean I haven't been thinking about it. I've come up with an idea which may help trace the fault(to the gauge, at least. I have a 12 volt adjustable transformer, which I thought would gradually increase the voltage to the gauge,with the view to protecting the gauge and any other sensitive electronics on the dash.
What do you think?