Coolant temperature always reads warm

marklawder · Post by **marklawder** » 13 Feb 2016, 18:43

So about a week ago I noticed the coolant temp was reading warm (3 oclock position) right away on a cold engine. I can let the car sit overnight and as soon as I put the key in, it runs right up to normal running temp without starting the engine. Thought this was the ECT sensor and I had a leaky radiator, so I didn't worry about it at the time. Just replaced the radiator today and swapped the ECT sensor and thermostat at the same time. Still having the same problem with the gauge. I tested both sensors for resistance and they both tested good based on the service manual resistance/temp chart. So I'm stumped. Got fresh coolant, new ECT sensor, new thermostat and problem was there with new/old radiators. Any ideas where to go next? What's weird is that most people say a bad ECT drives the gauge to full hot and mine is only halfway where it normally would be at temp.

Post by **dosbricks** » 13 Feb 2016, 19:03

What condition was the connector on the car where you plugged in the new ECT wires? The plastic is old and fragile and the brass connections can push backward in the connector and not onto the connector terminals on the new ECT. It may not be readily evident because that side of the connection faces downward.

Also did you replace with a genuine Volvo ECT?

marklawder · Post by **marklawder** » 13 Feb 2016, 19:37

Connections looked brand new on both ends, but I cleaned it out with some alcohol and qtips while I had the sensor off. Both sensors are OEM volvo.

Post by **jreed** » 14 Feb 2016, 05:29

One test that might help is to disconnect the ECT from the connector and then see if the temperature gauge still reads at 3 o'clock. If it does, then there may be a problem with the wiring from the connector to the gauge or the gauge itself.

marklawder · Post by **marklawder** » 14 Feb 2016, 07:20

Yep goes right to 3 o clock with the sensor unplugged. Sounds like I need to pull the cluster and start checking wires, fun

Post by **erikv11** » 14 Feb 2016, 08:46

Just curious: turbo or non-turbo? Mileage?

marklawder · Post by **marklawder** » 14 Feb 2016, 10:50

95 850 NA, about 200k miles

marklawder · Post by **marklawder** » 15 Feb 2016, 19:24

Hooked up a scangauge and it's showing proper operating temperature from the ECT, reads from cold and warms up to the thermostat opening at 190F, so the sensor looks like its reporting OK to the ECU. Seems to be a connection issue behind the cluster, see video. Still not sure why the gauge shows 3 oclock when off and cold, but I don't really understand how it works really either.

https://www.youtube.com/watch?v=a-18gNf ... e=youtu.be

Cees Klumper · Post by **Cees Klumper** » 16 Feb 2016, 11:47

Maybe it's the gauge that is broken ...

Post by **misha** » 16 Feb 2016, 13:27

With vol-fcr or at a dealer you can read codes from instrument cluster.