COOLING VOLVO 850 1997

MOR80 · Post by **MOR80** » 11 Jul 2026, 12:13

Hi;
My cooling fan don't work, the "IN" on relay cooling is for 12v ?

https://www.matthewsvolvosite.com/diagn ... fan-relay/

best regards

aeg · Post by **aeg** » 11 Jul 2026, 20:13

No. "30" is +12V from the battery. "IN 1" is grounded by the ECU to activate the fan at low speed. "IN 2" is grounded by the ECU to active the fan at high speed. "IN 1" and "IN 2" are both open-circuit when the fan is off. The relay supplies +12V to "OUT 1" or "OUT 2" to operate the fan according to the requested speed. Only one of "OUT 1" or "OUT 2" is active at any given time, with "IN 2" taking priority over "IN 1".

: fan-000c.jpg (29.57 KiB) Viewed 1531 times

Post by **scot850** » 11 Jul 2026, 23:11

Check the usual suspects first:

1) If it is similar to the petrol engine check coolant temperature sensor (ECT) by the thermostat. I am not familiar with the diesel 5 cylinder engine so I am not sure if it has the same layout. If it has, the coolant sensor has a poor design for the connector mounted to the rear of the power steering pump. The sensor can also fail or go out of range to activate the cooling fan.

2) Check the fan relay for corrosion on the pins and that the relay works as mention by aeg.

Good Luck!

Neil.

Post by **jreed** » 12 Jul 2026, 06:51

In addition to the above suggestions I would recommend checking the pins in the connector to the relay are in good condition in particular the insulation around the pins. My '97 had disintegrated insulation that allowed the metal pins to move away from the contacts in the relay, preventing a good connection and preventing the fan from turning on. Some photos and repair information is available here:
viewtopic.php?t=101867

MOR80 · Post by **MOR80** » 13 Jul 2026, 13:33

Thanks, i have 12V in 30A, but the cooler does not work, i'm going to change the relay...

MOR80 · Post by **MOR80** » 24 Jul 2026, 11:34

The engine keeps overheating; it's not the head gasket or the radiator.

PatternFlyer · Post by **PatternFlyer** » 25 Jul 2026, 01:28

Funny thing about Volvo. 99 V70XC has opposite color wiring on that input.

PatternFlyer · Post by **PatternFlyer** » 10 Aug 2026, 14:02

https://www.ebay.com/itm/143463175137

This is the same connector that is used for the input on the relay. (2 pin in the middle)

MOR80 · Post by **MOR80** » 21 Aug 2026, 09:39

Thanks, i buy it for test...
No more overheated now, but the cooler don't work...

Post by **jreed** » 22 Aug 2026, 05:36

MOR80, you're saying above that the cooling fan is not turning on? If so, have you tried connecting 12V directly from the battery to the fan to verify that the fan motor works when power is applied?