Radiator fan turns on after car off, drains battery

mmeisner · Post by **mmeisner** » 22 Feb 2006, 10:21

So that's the basic problem. I'm thinking it has to do with the Radiator fan switch/relay thing. I unplugged two of the three plugs directly above the fan, and the fan no longer turns on at night, nor does the battery die. Does this sound like the problem?

btw it's a 97 850 non-turbo

dpauto.com · Post by **dpauto.com** » 22 Feb 2006, 10:59

You could have a bad rad. fan relay which mounts directly on top of the fan by shroud.

Regards,
Dave

mmeisner · Post by **mmeisner** » 22 Feb 2006, 11:04

Would that cause the fan to turn on randomly? Any way to test the radiator fan relay?

dpauto.com · Post by **dpauto.com** » 22 Feb 2006, 11:55

That is a good question.

Your radiator fan relay is a two stage (speed) relay. It constantly has a 12v feed. As soon the ECU provides low or high speed ground signal to it, it will energize the fan accordingly. The ECU uses various sensors to energize the relay.

Now with your problem: Fan continuosly stays on after engine shuts off. Is it the ECU or the relay ? 95% of the time its the relay gets stuck. How to test this ... it's simple.

Allow a few minutes after you shut off the engine. While your fan is still running, disconnect the connector that has the yellow and yellow/white wires from the relay. If the fan still stays running, then you know for sure the relay is defective.

But if the fan stops running, then either the ECU is still providing the ground signal to the relay due to shorted sensors in the system OR simply because while you wiggling the connector, you unstucking the relay.

Regards,
Dave

mmeisner · Post by **mmeisner** » 22 Feb 2006, 12:30

Thanks a lot DPauto. I'll try this when I get home. One thing to note is that the fan turns on intermittently...like it would turn off when I shut the car off, but in the morning I'd go out to start it and would be running. I'm pretty sure you're right though.

Ghassan · Post by **Ghassan** » 24 Feb 2006, 11:18

I had the same problem on my S70 T5 5 years ago. I will check my reciepts and get back to you.

tdramer · Post by **tdramer** » 27 Feb 2006, 10:12

If you Google Volvo & recalls you'll find the info on the recalled fan switch. Good luck!

petershen1984 · Post by **petershen1984** » 26 Dec 2006, 07:02

You can tell you have a bad relay by shaking it and listening for "loose parts"... I wish I thought about accessing the battery or the relay when it happened to me. Now my cooling fan still works with a slightly noisy bearings!

By the way, disconnecting the FAN 1/2 connectors in the middle was NOT a smart thing to do. I have found the fan to stop spinning when I removed the pin going into FAN 1 (low speed signal). I was only intending to do a quick drive home, but I thought I was good when the fan started spinning again to cool off the coolant.

Now though, the fan was operating because (technically) it was energized by the FAN 2 signal (high speed), which I thought, hey- that's normal. However, because FAN1 had been disconnected, it didn't operate when it was supposed to, and allowed the coolant to get hot enough to activate stage 2 (which I didn't know at that time).

I was warned of this after only a few days of commuter driving. The very next time I started the car, the coolant light had illuminated to warn me of an empty reservoir tank.

I keep 4 liters (a one gallon coolant container jug) of water in the trunk in the event I needed to top off coolant and windshield wipers. I immediately popped the hood and filled the reservoir to the brim, and of course, reconnected the fan plug.

The reason water was consumed is because, without the fan running in stage 1, the radiator failed to dissipate the heat removed from the engine. As such, the coolant fluid continiously recirculates within the engine coolng path, but the radiator is not much help removing the collected heat. Thus, the heated water reenters the engine. It's a recursive process that ultimately causes the coolant to boil and evaporate. But all this time, it is the water that's still in the system maintaning the perpendicular indication on the thermostat switch, even though electronic sensors have already sensed an abnormality and activated the cooling fan at high speed.

God bless the idiot lights!

Post by **MadeInJapan** » 26 Dec 2006, 07:43

The radiator fan usually stays on due to a faulty coolant thermostat or temp. sensor or both. Temp is read too high even though it might not be.

mkanjaria · Post by **mkanjaria** » 11 Jul 2007, 16:09

hi guys ive got a similar problem with my s40 the problem is that the fan stays on even if i put the knobs on 0 fan speed and the fan doesnt turn off when the car is on but does when the car turns off.
i went to the dealership and asked them to sort it and the gave me the following list of parts to get:
level sensor
particulate filter
control-----------bought this but problem still persists
transistor
totalling