94 850 cooling fan will not turn on,RESOLVED bad ECT Topic is solved

jline · Post by **jline** » 25 Aug 2010, 17:10

My coolant began boiling out every so often and then realized my cooling fan wasn't turning on. I then replaced the relay and the fan although both original parts were fine and still worked after I bought replacement parts. And still now after replacing both the fan and the relay still no working cooling fan. I'm thinking about trying to rig a wire from the fan straight to the battery but thought I would see if anyone had a solution. I'm assuming now that it has to do with the other wires connected to the fan or some hidden fuse I don't know about. Any ideas?

Post by **Ozark Lee** » 25 Aug 2010, 20:20

The only fuse in the cooling fan is a "Fusible Link" which is a lump on the red wire going to the relay.

It is not uncommon for the fan to not come on if the air conditioning isn't on unless you are in heavy traffic. That said you seem to be overheating.

How is the temp gauge behaving?

...Lee

jline · Post by **jline** » 25 Aug 2010, 23:25

I also replaced the themostat before replacing the other stuff but the temp gauge doesn't really register anything and stays at the bottom unless Im driving around the city with a lot of stop and go. Then it starts to get up to where it should normally be in the middle? then the coolant might begin to boil. Perhaps it will kick in when ive been driving around but i really doubt thats going to happen and not sure whats my next move...

grapson · Post by **grapson** » 26 Aug 2010, 05:10

Hi jline

I had the same problem with mine - the temp gauge showed a lower temp all the time till one day it boiled over. What I didn't realise was that having my aircon on most of the time was saving me (because it ensured that the fan was on permanently. It turned out that the temperature sender (sensor) immediately under the thermostat housing was the culprit - it was all gunked-up with dried coolant. Anyway, had it replaced and temp guage returned to its normal position and no more boiling.

grapson · Post by **grapson** » 26 Aug 2010, 05:29

Hi again, jline

Just checked my invoice from the Volvo dealer regarding the above problem. It said "checked for fault codes - found 1.2.3. ECT sender. Checked ECU - 5V okay. Checked temp sensor - out of tolerance. Supply and fit new ECT sensor. Erased fault codes. Road tested - all okay. Checked fan operation - okay". I'm no mechanic, so thought I'd give it straight from the horse's mouth just in case I got the location of the sensor wrong. Good luck!

Post by **LamboSE5** » 26 Aug 2010, 10:53

Hey Jline,

When I bought my 98 S70 it had problems 'overheating' and on our test drive the coolant boiled out over the closed cap after we stopped and parked the car.

The problems were:

The cooling fan motor (only the motor was not working). So I took out the shroud and fan, and replaced the motor.
The cooling fan fuse, it was blown - no question about it. A 60amp fuse in the main fuse box. Don't know if its the same on an 850 - I mean if it has a cooling fan fuse. But you may want to check it out

These two things solved my overheating problem.

Have a good day everyone.

Post by **jblackburn** » 26 Aug 2010, 11:41

l replaced the themostat before replacing the other stuff but the temp gauge doesn't really register anything and stays at the bottom unless Im driving around the city with a lot of stop and go

It sounds like you are in need of a new coolant temp sensor...that one isn't giving you a correct reading. This time of year, a stuck-open thermostat would still let the car warm up quicker than that.

While you are in there, do a visual inspection and make sure your current thermostat is actually closing.

jline · Post by **jline** » 26 Aug 2010, 12:44

sounds like ill be replacing the coolant temp sensor and hopefully it shall work thanks for all the help

jline · Post by **jline** » 27 Aug 2010, 19:20

I replaced the coolant temp sensor and the old one looked like it needed to be replaced anyway and now my temp gauge seems to be working normal again but I still have yet to see my fan turn on but my car does seem to be running better and no coolant has boiled out yet so im off to a good start. Ill chalk up the other parts I bought to preventive maintance thanks for all the help hopefully this is it

Reys · Post by **Reys** » 09 Aug 2013, 23:11

I drive a 96 850 turbo, anyone know if the cooling fan is supposed to stay on after you shut the car down? it turns off with everything when I shut the car off. There isn't any overheating happening from what I know...except the headgasket went and had to be replaced a short while ago, temp gauge never went past normal reading. new parts from rebuild include: ect,thermostat, water pump, volvo coolant (used prestone premix before & headgasket went...possible culprit??) i do hear the fan on occasion, temp gauge stays a hair above center, what do you guys think, everything seem good?