1994 940 cooling fan never comes on

[Free940]

I have a thread in the Showroom telling my adventures of getting this car running. It had been sitting for about 7 years. It now runs decent, but the cooling fan never comes on. I replaced the two speed fan relay and can now get both speeds if I short either of the two pin connectors to ground. But again, the fan never comes on when the engine gets hot. It wants to boil over so I shut it down. What would you recommend my next step be? Replacing the ECT sensor? I noticed their are other sensors related to the electric fan that are tied in to the air conditioner system (front lower condenser, right hand side, three pressure sensors). My AC does not work and appears to need recharging. Would the AC not working affect the electric fan not working? I have searched other threads and have not found a solution. I would appreciate your help.. the wife is no longer sharing my enthusiasm on getting this fine automobile road worthy.

[mocambique-amazone]

This model of a 940 runs really very hot.
Only with the grey cap of the cooling system it will work. The AC won't affect the tuning of the fan in a bad way.
The ECT will fail at age. Only use BOSCH, nothing else will work properly. I've tested a lot of brands, nothing will match the Bosch ones. Important at 95+ cars.
It's the ECT sensor under the runner cyl 4. The same that gives he information to the ECU and the EZK. The one in front.

The fan is controlled by the ECU and by the ACC.
Good luck, Kay

[Free940]

Thanks for the info. I will Trace my wiring and try to determine which of the many cooling circuits available for the 940 that I have.

[Jebus]

Do you have the diag flashy box thing on the left side suspension tower you can do this

copy and pasted from the tech section on the main site.

Turn the ignition ON to KPII and install the cable into socket 2 for fuel-injection-related tests.
Press the button three times for one second each time (waiting between >1 and <3 seconds before pressing again)
The diagnostic unit then sequentially tests the following components: engine coolant fan (if equipped), fuel injectors, idle air control solenoid valve, carbon filter solenoid valve (if equipped), cold start valve, radio suppression relay and fuel pump. No code is produced: you have to listen or feel each in turn to make sure it is operating.
Exit by switching off the ignition.

[Free940]

I located three sensors under the intake manifold.

The first two were near the #2 intake. From what I have read, the one on the top is the temp gauge sensor. The one below is the knock (detonation) sensor:



The connector fell off of the temp gauge plug leaving just the pins.



To the right of those two sensors (circled in yellow), near the #3 intake is what I believe to be the ECT sensor:



The brass connector contacts for the first two sensor were green.. It almost looks like they are made that way, but it might be corrosion. I was unable to reach the ECT sensor to remove the connector.

Maybe it's just a matter of cleaning the contacts?


I was unable to find any sensors on the radiator. There was a plastic plug at the top right though. Maybe a place for a temp sensor in another application?

So from what I see, the two pins, high and low speed, located on the dual speed fan relay module go to the same module that the ECT sensor wires go to and that module controls the fan?? I haven't looked, but I read that this module is located on the passenger side kick plate. Does this sound right? Please be patient with my assumptions, I am only guessing at this point. Figuring out this fan system is quite confusing to me. I am unable to find a complete wiring diagram that links all these sensors and modules up, although I have been shown some partial diagrams by forum members.

[Free940]

Originally Posted by Jebus

Do you have the diag flashy box thing on the left side suspension tower you can do this

copy and pasted from the tech section on the main site.

Turn the ignition ON to KPII and install the cable into socket 2 for fuel-injection-related tests.
Press the button three times for one second each time (waiting between >1 and <3 seconds before pressing again)
The diagnostic unit then sequentially tests the following components: engine coolant fan (if equipped), fuel injectors, idle air control solenoid valve, carbon filter solenoid valve (if equipped), cold start valve, radio suppression relay and fuel pump. No code is produced: you have to listen or feel each in turn to make sure it is operating.
Exit by switching off the ignition.

You were posting at the same time I was!

Not sure I have what you are talking about. Sounds like a diagnostic tool that I would have to buy?

[Free940]

Originally Posted by Jebus

Do you have the diag flashy box thing on the left side suspension tower you can do this

copy and pasted from the tech section on the main site.

Turn the ignition ON to KPII and install the cable into socket 2 for fuel-injection-related tests.
Press the button three times for one second each time (waiting between >1 and <3 seconds before pressing again)
The diagnostic unit then sequentially tests the following components: engine coolant fan (if equipped), fuel injectors, idle air control solenoid valve, carbon filter solenoid valve (if equipped), cold start valve, radio suppression relay and fuel pump. No code is produced: you have to listen or feel each in turn to make sure it is operating.
Exit by switching off the ignition.

Oh.. this must be what you are talking about. Pretty neat!

I will have to read up on how it works.

[Jebus]

its a built in little box that some models had, looks like this should be bolted to the suspension turret in the engine bay



haha as i was typing...

[Jebus]

The tech section on here goes though how to use it, can flash codes, clear code and run some self tests on the car,

Clicky to tech section

[Free940]

Originally Posted by Jebus

The tech section on here goes though how to use it, can flash codes, clear code and run some self tests on the car,

Clicky to tech section

The link didn't work, but I will find it. Thanks!