940 separate temperature gauge

[jpliddy]

Dave I've only just changed the thermostat fitted another genuine one

[Laird Scooby]

Originally Posted by jpliddy

But is there more complex things ive got to do to fix my problem

First you need to find out if the engine is actually getting up to temperature Jim, as i described with the infra red thermometer above.
If it's not, the gauge may in fact be working most of the time when it doesn't read zero.

[jpliddy]

The cabin gets hot dave so the heating is good any help there

[Laird Scooby]

Originally Posted by jpliddy

The cabin gets hot dave so the heating is good any help there

Absolutely no help at all Jim. You need to know what temperature the engine is reaching. Volvo heaters are generally pretty efficient and even with an engine temperature of 40C (way too cold for efficient running) you'll get a warm cabin.

[baggy798]

Originally Posted by jpliddy

Thanks for your thoughts everybody hi baggy your gauge looks good did you have a faulty gauge im thinking its not the gauge itself as I've changed it. But is there more complex things ive got to do to fix my problem

Nah, I changed it because the stock one isn't very accurate and heavily compensated, meaning it could be running 20° hotter or colder and you would never notice!

I would check the wiring for continuity between the cluster and sensor next. The two wires that go to the sensor (7/7) from the cluster are A12 (yellow-black) and A14 (yellow-white).

D24 wiring might be slightly different!

[jpliddy]

thanks to all of you .hi baggy i understand some of what you say im a carpenter so bit difficult i see A12 and A14 on the multi plug. where do i put my multi meter do i have the ignition on when testing the electrics .?

[Laird Scooby]

Jim, there's an easier way - unplug the sensor and fit a small value resistor (50-100 ohms) in the contacts in the connector plug, switch the ignition on and observe the gauge. Depending on the resistor value, it should go to about 1/2 - 3/4 of the way up. If you're in doubt about which resistor to buy, PM me your address and i'll send you one.

That will test the gauge and the wiring, if it doesn't move then there's another fault which we can deal with after. If the gauge moves then it's either the sensor or the thermostat.

[James_EG_940]

I have a very similar problem. My temp gauge hasn't worked right for a long while and I'm pretty certain it's not the gauge or the instrument cluster.

Almost certainly the cabling on mine as the resistance across the sensor checks out ok and the dial sometimes jumps into life with jolts of the engine (indicating a dodgy connection in a cable).

Another way to measure the continuity of a long pair of wires is to short one set of ends together and then measure across the other end. It should be very low resistance (ie below 5 ohms). If not you know there is a problem and can investigate further in that direction.

I plan to sort mine out once I stop the coolant leaking out onto my feet!

[jpliddy]

hi james is the coolant leek at the heater control valve just above your left foot
i replaced mine when they where available from volvo but there are other fixes on this forum somewhere

[Laird Scooby]

Originally Posted by jpliddy

hi james is the coolant leek at the heater control valve just above your left foot
i replaced mine when they where available from volvo but there are other fixes on this forum somewhere

Sent you an email last night Jim.