My original ECC just burnt out at 238k. Replaced it with a used one. Everything works except auto fan position. Get the two blinking lights and code 135 in B-1 socket. That code is "no signal from engine coolant sensor". The dash temperature gauge works fine, so the sensor appears to be sending a signal. Is the problem in the replacement unit or something else. Thanks

Hi,

On many cars there are two separate sensors doing the coolant readings.
The gauge one works in a completely different instrument electronic system and is working with voltages and current to the gauges.

The fuel management one is changing is resistance that starts out a lot higher values and drops in many cases with temperature increases.
The sensors can be built the other way around so they can be specifically locked to each manufacturer fuel systems.
It’s called an ugly word “Proprietary.”
Humans make the world more complicated to some extent or different because there are more than two ways to do something, past right or wrong.
We humans come by it naturally as the whole.
No two things are exactly the same or perfect, so with that, it’s game time to keep us from getting bored.

Phil

Hi David,

Here's the info on the 850 ECT:

Volvo P/N 3545031

Temp F. / Resistance in Ohms
32F 7300
68F 2800
104F 1200
176F 300
212F 150

Measure your sensor values first.

Good luck, Bill