96 850T5 engine temp gauge intermittent problem

berk850 · Post by **berk850** » 26 Oct 2013, 15:13

Hi

I noticed today when I was driving that the temp gauge was all the way down, as is the ignition was off. After a few minutes whoops it was back on, pointing 3 o'clock as it should. The car ran fine all the time, did not seem like the engine was running rich or anything so I do not think that the engine was receiving the wrong temp. data. No check engine light either. What contacts should I check?

When this problem occurred, I had recently gotten the car back from my mechanic, who had changed the timing and the aux. belt. Could not take the car back to him as he had shut down for the weekend and I am due for a trip tomorrow. Is this a pure coincidence or do you have to disconnect some cables when you're changing the T-belt that may cause the problem with the temp. gauge?

I should also say that the temp sensor that sits by the thermostat is only two years old.

Thanks in advance.

Post by **Pauloil** » 26 Oct 2013, 16:16

unplug the contacts to temp sensor and clean with electric contact cleaner. I doubt the mech. touched this part of car. if the sensor were bad often the fan runs after you shut car off. the sensor could be going bad. how is the fluid level?

Post by **rspi** » 26 Oct 2013, 19:06

Seen this in a car 2 days ago. I also chased this problem for 3 months earlier this year. What I finally found was a bad wire at the top of my cluster plug. The wire harness has been sitting up there with weight on it for 19 years. The thin wires finally broke within the coating causing cluster reading issues. I pulled another plug from a car in the salvage yard that looked like it didn't have the pressure as mine did. I made the harness longer and spliced them together with telephone wire splices. No issues since.

On a good note, the OBD-II port still reports good temp readings. So if you have a ScanTool that can read live date, you can check it as often as you'd like with it and reduce the fear. I use a ScanGauge II all the time so things have been fine for me.

http://volvoforums.com/forum/volvo-850- ... post329194

berk850 · Post by **berk850** » 26 Oct 2013, 20:50

rspi: Do you mean the plug at the back of the instrument cluster?

Post by **rspi** » 26 Oct 2013, 20:59

The plugs are actually on top of the cluster.

difflock54 · Post by **difflock54** » 26 Oct 2013, 21:09

Yes to all the above comments but can you advise us if:

The waterpump got replaced along with the new timing belt,serpentine belt and the coolant required to be topped up ??

If the pump was done the thermostat may now be sticking in the full open position which make the engine run cooler for a longer period before the sensor may operate and show at 3 o'clock on the gauge.

berk850 · Post by **berk850** » 27 Oct 2013, 13:09

Thanks for all the replies. The coolant level is at max and as far as I know it's self bleeding so no worries there.

The problem has not come back, which is really annoying. Nothing worse that intermittent electrical problems.

The wires by the temp. sensor contact near the intake manifold look really worn, there was even a spot there where you could see the bare wire. I fixed that temporarily with some electric tape.

If the problem reappears I will loosen the drivers side of the dashboard and feel the contacts on top of the instrument cluster and see if that makes a difference and the temp gauge jumps to life when I touch the contacts. If it does I'll get another harness as rspi did and fix the issue.

Where is the other end of that harness by the way? Maybe somewhere more accessible so that I can clean those contacts just in case.

Post by **rspi** » 27 Oct 2013, 13:30

Well, The Volvo wire harness behind the dash is MASSIVE. Not sure there is a "check the other end" option. The problem I had was the wires broken at the connector. No remedy for that on the other end.