Cooling fan still not working...

rombe3jr · Post by **rombe3jr** » 11 Jun 2007, 13:01

1995 Volvo 850 GLT sedan 150,000 miles. Hey forum! This is related to my previous post https://www.matthewsvolvosite.com/chat/p ... highlight=.

I bought a used fan relay for my radiator cooling fan, which luckily had the same part number, replaced the old one and... the fan still doesn't work. So to go over the history here: I've hooked up the battery to the fan straight and it works. Now I've replaced the fan relay and the fan still does not work on its own, causing it to overheat and coolant to spill over. I'm going through a gallon of coolant a week to keep this thing going! What should I try next? Thanks for your help!

Post by **Ozark Lee** » 11 Jun 2007, 15:08

It could be that the used relay is bad too or, even more likely, the connectors are corroded.

Have you gone after it with a voltmeter?

In your original post you indicated that you can hot wire the fan and it runs, why don't you leave it hot wired to a "key on" fuse until you can correct the real problem. It will save a lot on antifreeze and also the very real potential of blowing a head gasket.

...Lee

Trilarry · Post by **Trilarry** » 11 Jun 2007, 15:34

Try This, push the terminal out of the fan relay connector. Two cone shaped terminals should appear out of the connector. Then connect the terminals into the relay with out the connector body. If this works it's just a bad wornout connector that is causing your fan not to work. I had the same problem.

Sometimes the plastic supports in the connector body that holds the terminals in place wear out and it allows the terminals to not have a good connection.

For a quick test turn the AC on
Tri

Post by **JRL** » 11 Jun 2007, 16:19

rombe3jr wrote:1995 Volvo 850 GLT sedan 150,000 miles. Hey forum! This is related to my previous post https://www.matthewsvolvosite.com/chat/p ... highlight=.

I bought a used fan relay for my radiator cooling fan, which luckily had the same part number, replaced the old one and... the fan still doesn't work. So to go over the history here: I've hooked up the battery to the fan straight and it works. Now I've replaced the fan relay and the fan still does not work on its own, causing it to overheat and coolant to spill over. I'm going through a gallon of coolant a week to keep this thing going! What should I try next? Thanks for your help!

New coolent temp sensor

Trilarry · Post by **Trilarry** » 11 Jun 2007, 20:27

JRL wrote:
rombe3jr wrote:1995 Volvo 850 GLT sedan 150,000 miles. Hey forum! This is related to my previous post https://www.matthewsvolvosite.com/chat/p ... highlight=.

I bought a used fan relay for my radiator cooling fan, which luckily had the same part number, replaced the old one and... the fan still doesn't work. So to go over the history here: I've hooked up the battery to the fan straight and it works. Now I've replaced the fan relay and the fan still does not work on its own, causing it to overheat and coolant to spill over. I'm going through a gallon of coolant a week to keep this thing going! What should I try next? Thanks for your help!
New coolent temp sensor

The Coolant Temp sensor if was bad would cause your fan to run continuously because the fan comes on when you get a low or no signal from your temp sensor (code 116 or 117). For example if you unplug your ECT your fan would automatically come on because there is no signal. It is a default to keep your car from overheating. Any Codes? if not check your connectors as stated above. Not trying to be argumentative.
Tri

Tsquared · Post by **Tsquared** » 12 Jun 2007, 12:42

Trilarry,

The other way it could be bad is if it was a closed ckt. My understanding this is just a basic one stage thermocouple that is normally closed causing the fan to be off. When it heats up it goes open causing the fan relay to turn on the fan.

Please correct me if I am incorrect, I pulling from my memory as I don't have my manual with the circuity nearby.

T

Trilarry · Post by **Trilarry** » 12 Jun 2007, 20:50

TSquare, I would assume the same thing. But after troubleshooting why my fan ran continuously, I found that this sensor works oposite to what you would assume. Here is an excerpt from the manual. Note the 4 cylinder Volvo's ( I assume 240's) have this thermalcouple you mention but the 850's and S70's have one that works by resistance. The fan runs when there is low or no resistance. Here is the excerpt: Please correct me if I'm wrong.

Engine Coolant Temperature Sensor
Engine Coolant Temperature (ECT) sensor is a negative
temperature coefficient type, meaning its resistance lessens as
temperature increases. Four cylinder sensor unit has 2 resistors. One
resistor is connected to fuel injection ECU and the other resistor is
connected to the ignition ECU.

Buck380 · Post by **Buck380** » 12 Jun 2007, 21:55

You never said, but I assume the fan turns on when the A/C is switched on.
If not, do you have continuity from the unplugged black ground wire to the engine block?
Have you checked for codes?

Tsquared · Post by **Tsquared** » 13 Jun 2007, 15:19

Trilarry wrote:TSquare, I would assume the same thing. But after troubleshooting why my fan ran continuously, I found that this sensor works oposite to what you would assume. Here is an excerpt from the manual. Note the 4 cylinder Volvo's ( I assume 240's) have this thermalcouple you mention but the 850's and S70's have one that works by resistance. The fan runs when there is low or no resistance. Here is the excerpt: Please correct me if I'm wrong.

Engine Coolant Temperature Sensor
Engine Coolant Temperature (ECT) sensor is a negative
temperature coefficient type, meaning its resistance lessens as
temperature increases. Four cylinder sensor unit has 2 resistors. One
resistor is connected to fuel injection ECU and the other resistor is
connected to the ignition ECU.

OK, I will buy that. Does your manual list the resistance at a set temperature? It still could be braking down.

Trilarry · Post by **Trilarry** » 13 Jun 2007, 20:38

T, this is the resistance at a certan temperature. I agree it could be breaking down but he said it overheats and if it does that the resistance would be so low that the fan would come on. If the ECT broke down inside and the 2 wires crossed....maybe? I'm not that great with electronics but I guess it could happen? There is still alot of questions ROMB3jr hasn't answered. I await them. Thanks for getting me thinking.

Tri

ENGINE COOLANT TEMPERATURE SENSOR RESISTANCE TABLE
Temperature F ( C) Ohms
32 (0) .............................................. 7300
68 (20) ............................................. 2800
176 (80) ............................................. 300
212 (100) ............................................ 150