940 & 960 Overheating help - electric coolant fan not working. Looking for relays

Overheating help - electric coolant fan not working. Have changed coolant sensor under the third injector. Changed temperature sender/sensor. Changed new radiator. New thermostat.

Two relays operate the fan. Where can I source new relays locally (Vic - traralgon). Or possibly loan spares?Wondering about anyone local who could loan me two electric fan relays to try? Also, is this circuit fused on the fuse board behind the ash tray?

Any info would be much appreciated.




  • Check to see if the relay can be repaired (pull it apart)

    Check fuses too

  • fan is not triggered until 105-107c for low and ~115C high as measured via the head based sensor

    Ac will trigger fan based on AC pressures, just starting the compressor does NOT trigger the fan

    You running 50/50 coolant mix? Anything less will not have a high enough boiling temp and will put the system under excessive pressure

    Fan is triggered by the ECU... so easy enough to put a 12v led onto the pins (you have a wiring diagram handy?) To see if the ecu is triggering the fan at all

    Relay failure on these is highly uncommon

  • ...I am trying to loan the two relays that control the fan to check their not the prob....connected the fan direct to battery works ok maybe a local volvo owner has spare relays...I will attempt to get a wiring diagram. Any clues where the ecu is?

    Will get new glycocole coolant tomorrow .

    See what happens air con has not worked for years possible regas..

    Thanks for assistance will keep you posted..

  • Is it a 940 or 960? What year?

    I can pull the wiring diagram for you easily

  • It's a 940..checking the wiring I don't where coolant fan fuses ecu equipment are positioned. Unsure.

    Plan 14b is to drive to melb..I'll take the thermostat out... and get a volvo mechanic to check...thanks for your info I'll keep you posted when I have solved...Have a great 2022👍

  • I wouldnt take the thermostat out personally you might find it will overheat even worse. The thermo relays are located near the battery tray (N/A models).

    Pins 10&11 on the jetronic ecu (located in the inner kick panel) control thermos. If you earth either of those pins the thermofans should kick on. May be able to rig it up to a switch temporarily.

  • This is from the 940 YM 94 wiring diagram. Colour codes may be different on other year models.

    2/11 = fan relay

    4/23 is the ECU

    7/38 is the low speed pressure sensor

    7/40 is the high speed pressure sender

    ECU is on the RH side below the 'A' pillar, between the accelerator pedal and door opening on RHD cars

  • I'm back...today..another attempt disconnected both coolant fan relays removed the outer cover..both relays checked out electrically ok ..physically no burnt windings and contacts are all clean..slightly adjusted relay contacts possible contacts weren't making... advice by my big bro. disconnected sender plug shorted the sender plug to earth...1 high 1 low..surprise the fan worked on high/low..

    All reconnected fan does not work.

    When the engine is running as the temp gauge rises slowly..when it's appears hot on the gauge...turn the indicators on or touch the brake pedal the temp gauge.flick flick toward hot..possible ecu is freaked out wondering again..

    Thanks...for your input

  • Just confirming it is pins 10 & 11 on the lh 2.4 ecu

    Simplest fix is to add a T piece into the lower hose with a 82C switch, so if and only if water entering the engine is above 82c then it turns on the fan on low until the water temp leaving the radiator is under 77c

  • Thanks again !!!!!!

  • Further to overheating ...drove to Berry's Volvo Mitcham on Wednesday...problem was loose radiator resevore hose clamp...and temp gauge sensor was wired incorrectly

    local mechanic assured me it was correct...

    plus installed new temp and fan sensors..all fixed temp gauge stopped flicking..

    Thanks for all your helpful info...

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