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Volvo 940 - Electric Radiator fan only works when A/C is on

ChristianFlores

ChristianFlores

New member
Joined
Mar 14, 2023
Please, help me with this. My 940 non turbo is a mess... In the last 4 months, when the engine is getting in temperature, the low speed of my electric fan doesnt work. the Electric Radiator fan only works when I turn on the A/C. Do you have any idea of what could be the problem? Should I change the entire system for a Mecanical fan clutch? I live in a very hot city, so, I'm afraid if I dont fix it, it will mess my engine seriously (if it's not already messed up). Thanks in advance for your time and help.
 
PCH said:
If the temp gauge doesn't go past the middle then you don't have any problem.
Click to expand...

If i dont turn on the A/C, the gauge tends to go way over the middle. In a couple of times, the engine overheated. If i turn on the A/C, the gauge stands in the optimal temperature, but from time to time it goes a little bit over the middle.
 
PCH said:
Run the diagnostic mode 3 to see if the ECU can activate the fan: https://www.volvoclub.org.uk/faq/EngineOBDCodes.html#FuelInjectionandIgnitionDiagnosticCodesi
If not- inspect the wiring by the fan relay.
Click to expand...
There are only 2 wires going to the fan relay to trigger it. If the AC is triggering the fan, those have to be intact. It sounds more like an ECT sensor that is out of range, or, a defective ECU. It could even have a non-fan driver ECU in it. OP, check what part number is on the ECU.
 
Is it a Regina car or Bosch ? If Regina car the radiator switch is the only thing that triggers the fan relay for none ac fan activation. The coolant temp sensor or ecm does not control the fan on Regina cars! I have proven this but following the wiring from the relay back to the car/ecm. Never even goes to ecm.
 
rwturbo said:
Is it a Regina car or Bosch ? If Regina car the radiator switch is the only thing that triggers the fan relay for none ac fan activation. The coolant temp sensor or ecm does not control the fan on Regina cars! I have proven this but following the wiring from the relay back to the car/ecm. Never even goes to ecm.
Click to expand...
What temp does the radiator switch turn on at? Just curious, might use it for my High speed circuit.
 
Indeed. My Volvo is a Regina, but apparently the last owner mixed the cables from the radiator of a 1995 Volvo , connected them to a 1 speed fan and mixed with a lot of relays in order to make it work. I'll throw it all to hell and this weekend I'm going to rewire the whole thing with a new 1995 relay and a 2 speed fan. This is the wiring diagram, wish me luck:
IMG-20240331-WA0007.jpg
rwturbo said:
Is it a Regina car or Bosch ? If Regina car the radiator switch is the only thing that triggers the fan relay for none ac fan activation. The coolant temp sensor or ecm does not control the fan on Regina cars! I have proven this but following the wiring from the relay back to the car/ecm. Never even goes to ecm.
Click to expand...
 
I don't have my 90 Regina wiring diagram with me; my 745 has a mechanical fan but I plan to retrofit the 7/9 E-fan and relay.

One thing looking at your diagram; I doubt the factory used a physical switch to actuate a standard auto relay WHICH then actuated the standard fan relay. From memory, the factory E-fan cars have a fusible link powering the large relay. In the BOSCH cars, all the fan relay needs is a ground path (via pressure switches and ECU) to fire the fan/speed. Why not do the same? I am not a fan of manual switches as it requires the driver to REMEMBER that they need to control engine temps.

One of the very first Sr. Engineers I worked with in my career taught me "Simpler is Gooder".
 
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