Just picked up a 97 OBW w/ 180K the issue was overheating. Before I confirm the HG issue I did a visual and noticed the fans on the radiator are not spinning at all even at temp. What test can I do to see if they come on manually. Thanks

Turn on the AC!

 

If they don't come on, check the relays in the engine compartment fuse/relay box. If you jump the power contact with the relay pulled you should power up the fan, one relay for each fan.

When I turn on the AC the fans do not come on. The AC is not working as well just warm air and I do not see the AC clutch turn on. Sounds like a relay. Not sure how to jumper though

1) I replaced every relay in the engine compartment fuse box from my work subaru, the fans will still not come on.

2) Checked all the fuses

3) to make sur ethe box was gettig power I pulled the fuse for the hazards while they were on and they went off.

4) I jumpered the fans straight to the battery, they work

 

Why won't my fans come on......

Looking at my data it shows that the relays are controlled by grounding the relay coils through the ECU. If I remember correctly the ECU depends on the coolant temp sensor to show when to turn the fans on. They should have turned on with the AC I think. To see if the fan circuits are ok you could try grounding pins 73 (grn/red) and then 74 (red/blu) on the ECU to see if the fans work then. If that checks out then you may want to check the coolant sensor next to see if that is working as it should be. The ECU may also have a internal problem causing this trouble.

Where are these pins?

The pins are on the ECU, which should be under the right side of the dash if my info is correct.

Ok, so do I strip the wire going into the ECU and touch it to the frame. Or can I pull it from the plastic connector?

You should be able to stick a probe tip or wire end in the connector while it is still connected to the ECU. Then touch the other end to ground. If the fan works you know that part of the circuit is ok. I wouldn't damage the insulation of the wire if you can help it.

OK, which connecter. I took a pick. The factory manual says its a blue connector. Is the ECU connector or that one in the upper right.

The pins should be in the blue connector connected to the ECU which is shown on the left side of the picture. You may have to add the pin numbers of other connectors to get the right pin number or the numbers may be marked on the connectors. Look for the wire colors I listed earlier.

Here is my deal now. The pins from the diagram are not lining up with the colors noted by your entry and other entrys in the service manual. hmmmm what to do. I looked everywhere for numbers, nothing

Let me make sure I have my facts right. The car you have is a '97 OBW, with a 2.5 liter engine?

Correct. There are soooo many wires

Well after comparing the 2.2 and 2.5 liter drawings it appears the wiring is the same for the fans at least.

 

Since you can't locate the wires we need to get on at the ECU, lets try at the relay. The main fan relay is in the power panel and is at the front of 4 fan relays in a row. Can you locate that and tell me what the wire colors are going to the bottom side of that relay slot.

OK, I opened up the fuse relay box under the hood and located the AC Main Fan Relay 1. There are 4 wires. R/Blue Y/G W/Blue and White. I tried to locate them in the ECU bundle of wires with no luck.

You stated that one of the wires is red/blue and that matches one of the wires my data showed that goes to the ECU. You should be able to tie that wire to ground and the main fan should turn on if the rest of the circuit for it is ok.

Looking at my data it shows that the relays are controlled by grounding the relay coils through the ECU. If I remember correctly the ECU depends on the coolant temp sensor to show when to turn the fans on. They should have turned on with the AC I think. To see if the fan circuits are ok you could try grounding pins 73 (grn/red) and then 74 (red/blu) on the ECU to see if the fans work then. If that checks out then you may want to check the coolant sensor next to see if that is working as it should be. The ECU may also have a internal problem causing this trouble.

 

I was lookeing at the ECU backwards. I grounded those pins and the fans do come on. Whats Next

So now you know the fan circuits are good. The real problem is due to either the coolant temp sensor for the ECU isn't working as it should be or the ECU circuit for the fans is bad. The first step is to see if the sensor is the correct resistance when the engine is at normal operating temperature. One thing to check is make sure the connection to sensor is clean and tight. Sometimes that is the trouble.

 

I don't have access to my service data right now so I can't tell you much more info on it. I will be home on Wednesday if you don't get more help on this.

 

OB99W- Hellllp!

Since I have the same working OBW,

1) I switched the ECU out, no change.

2) pulled the connection off the temp sensor, I checked the voltage on the wire. I am seeing 10 volts on the wire

Having 10 volts there sounds about right. Since you have another vehicle to compare with, check what the resistace of the sensor is on the good vehicle when the engine is warm and the wire connector removed. Then measure the other sensor the same way. See if they compare the same. If the resistances are within around 10 ohms of each other then the sensor is probably ok. Another way of doing this is to compare the voltage at the sensors with everything hooked up correctly.

 

I am guessing that the resistance of the coolant sensor may be around 30 ohms when the fans are supposed to turn on. You could place a resistor across the sensor leads to see if that turns on the fans.

What I thought was the coolant sensor was actually the engine temp sensor. Went to the dealer and they showed me the coorect part. Where is the coolant sensor

BREAK THROUGH --- I unplug the coolant temp sensor and when I trun the AC on the fans now turn on. Would this confirm a busted temp sensor...

Nope, I had another connector off as well and I then plugged in the old coolant temp sensor. When the middle engine harness connector is off the fans turn on, I also then hear the 1st Relay click to turn the fans on. I must have a short somewhere

I doubt there is a short causing this trouble but there could be a bad connection somewhere. Did you try measuring the resistances of the sensors and compare them to each other?