Cooling Fan Problem! The only Subie left here.

[vincentwl]

Hi All, I've been visiting this forum for a very long time although this is my first thread. I've got this First Gen Legacy with 220,000km for a year, and have 235,000 km on it now. It is 2.2L NA with 5 spd MT and AWD. It is fabricated in 1995. I am not sure the original market of it, maybe Russia, Vin code tells the model is BC7. I have done some modifications to this car and the car drives well in a very long time.

Unlike most of the friends here, the Legacy and me are in China. I'm pretty sure that this legacy is the only one that still running in my city now, furthermore, one of less than ten(or even five) in the whole country. Maintaining this vehicle is quite difficult, even the dealer don't know how to repair it. Vehicles like this old Subie, are not imported officially. I feel lucky to own one.

Recently, I lost the water temp gauge on the cluster. Thus I was doing some work on the electrical fix. Till now, A 15V 83F super capacitor is added to the battery for a steady voltage, and to support sudden electrical needs for acceleration or so. It works fine, but no significant improvement there.

I got a multimeter, then I measured the voltage that send to the one wire thermistor is about only 2V. After the installation of the super capacitor voltage stabilization mod is added, The water temp gauge could point to the right position occasionally, while pointed to cold otherwise. It will point to the middle in these conditions:
a. Release the throttle and slide with the gear on.
b. Pushing the throttle in reverse gear.
c. Stop in front of the red light.

It is really buzzing me. Thus I go to the groundings last night. I cleared two ground points on the strut towers. and check the fuse box. I have this unstable idle unstable problem. And I noticed that the rev will jump slightly with the click of AC Fuse No.3. Thus I took the fuse box up to check the connections, all seem good.

After all that, this morning when I start my car, I found out that both of the fans will be on with the key turned to ON, along with hard to start. Actually this happened last night in a very short time, I just reinstalled the fuse box, and it gone.

Thus I drove the car to a factory. They checked all the wires in the engine bay, remake the connectors of the temp sensor, tested with another good temp sensor. Still, the fans are on all the time as long as the key is turned to ON.

Here is some facts:

a. After the check of the wires, the voltage to the one wire temp sensor is going to 8-9 V, Thus the temp gauge is back with wrong position.
b. The A/C switch is gone. It won't light up and no relay clicks can be heard. Compressor is not working(cycling with belt) no matter how.
c. The GE ground point is well grounded to the battery terminal. However the chassis are not, there are about 1.5V between chassis to the battery negative.
d. Take out all the relays on the fuse box in the engine bay, the fans are still running, but the rpm seems lower. relays seem fine. Also some of the relays under the cluster are tested, found on for the main fan, but it is OK too.
e. Tested several pins on several sensors, the voltage of the ECU is sending is about 5.1V.
f. there is a grounding wire between chassis in the fuse box area and the battery. Heat is noticed on that wire. Disconnect that wire, the RPM of the fan seems lower. And there are sparks when connect it to the chassis, while the fan is running.
g. all these are observed with or without the super capacitor connected. Thus I think it won't do anything to the problem.

Another fact:

It has been a while, that the unstable idle will come with the clicking sound that from the left side of the cluster. This clicking also happens in the driving. But after today's engine bay wire check, it is gone for now.
check the video: http://www.youtube.com/watch?v=wr7ClWuY ... e=youtu.be


What I am going to do is grounding the chassis as best as I can. But no hope on solving this problem.

Any suggestions will be welcomed. Thanks in advance.


P.S. Under the strict laws and regulations in China, owning and maintaining an old car is very hard. Now I have to take the legacy to the government test center twice a year to get the permission to go on the road. And if the vehicle's mileage reach 600,000 km, it will be force retired to the garbage tray. I really want this one to run longer, please help me out!

[Legacy777]

Welcome to the BBS, even though you said you've been visiting for a while.

It really sounds like you may have a grounding issue. You should be checking the resistance of the wiring from the negative terminal of the battery to the various ground points on the chassis, engine, etc. In theory it should be 0 ohms or very close to that. If you see high resistance numbers, I'd suggest removing the bolt/screw holding the cable to the chassis and see if cleaning the connectors help. If not, I'd try running a redundant wire from the negative terminal of the battery to that ground spot. It may be that just cleaning the ground locations will help, but it's good to test with a multimeter.

Your description of the fans coming on and off, and staying on is what happens when the AC or defrost buttons are depressed on the HVAC control unit. It's possible the HVAC control unit is bad and may not be sending the correct signal to the fans. Is the AC compressor still cycling on and off?

Here is the diagram for the temp gauge. It uses a separate coolant temp sensor that grounds through the engine, so if the engine ground is bad, that could be affecting things.

http://www.main.experiencetherave.com/s ... iagram.jpg

[vincentwl]

Welcome to the BBS, even though you said you've been visiting for a while.

It really sounds like you may have a grounding issue. You should be checking the resistance of the wiring from the negative terminal of the battery to the various ground points on the chassis, engine, etc. In theory it should be 0 ohms or very close to that. If you see high resistance numbers, I'd suggest removing the bolt/screw holding the cable to the chassis and see if cleaning the connectors help. If not, I'd try running a redundant wire from the negative terminal of the battery to that ground spot. It may be that just cleaning the ground locations will help, but it's good to test with a multimeter.

Your description of the fans coming on and off, and staying on is what happens when the AC or defrost buttons are depressed on the HVAC control unit. It's possible the HVAC control unit is bad and may not be sending the correct signal to the fans. Is the AC compressor still cycling on and off?

Here is the diagram for the temp gauge. It uses a separate coolant temp sensor that grounds through the engine, so if the engine ground is bad, that could be affecting things.

http://www.main.experiencetherave.com/s ... iagram.jpg

Thank you very much. I've cleaned all the ground points in the engine bay today, and add a redundant wire between chassis and the terminal. Thus now I test the resistor between each points is close to 0 ohm, even with the metal part in the cabin, This give me more voltage on the cigarette lighter port from 12.8 V to 13.6V while the voltage on the battery is about 14V, with engine running. I will do a grounding kit later on. But according to the multimeter result, the grounding problem is gone.

I tested the HVAC control unit, it is all good, compressor will react with AC button, AC clutch can be heard with the button pushed.

Now I still have this problem, Both of the fans running, in their fastest speed I guess, while the key is turned to ON.
It is hard to start, due to that the fans take too much energy from battery while starting. This morning, I can't start at all, thus I take out all four AC relays in the fuse box, thus the fan will run much slower then I can start. After driving for like 3 km, I pulled over and installed all the relays back in case of overheating. I can't know the exact temperature of the engine due to that the temp gauge is still not right, it will point to a much lower position.

Further more, I think the ECU is reading wrong temp because when I start the car cold, the idle will drop to 750-800 very fast like it is already warm.

I guess the temp gauge will be right after the fan problem is solved, hope so at least.

Any more thoughts please?

[vincentwl]

Welcome to the BBS, even though you said you've been visiting for a while.

It really sounds like you may have a grounding issue. You should be checking the resistance of the wiring from the negative terminal of the battery to the various ground points on the chassis, engine, etc. In theory it should be 0 ohms or very close to that. If you see high resistance numbers, I'd suggest removing the bolt/screw holding the cable to the chassis and see if cleaning the connectors help. If not, I'd try running a redundant wire from the negative terminal of the battery to that ground spot. It may be that just cleaning the ground locations will help, but it's good to test with a multimeter.

Your description of the fans coming on and off, and staying on is what happens when the AC or defrost buttons are depressed on the HVAC control unit. It's possible the HVAC control unit is bad and may not be sending the correct signal to the fans. Is the AC compressor still cycling on and off?

Here is the diagram for the temp gauge. It uses a separate coolant temp sensor that grounds through the engine, so if the engine ground is bad, that could be affecting things.

http://www.main.experiencetherave.com/s ... iagram.jpg

Legacy777, I really appreciate your work here, I've been download all kinds of documents in this forum and from your website. I want to contribute too, kindly please download this 92-94 legacy FSM maybe you could put it onto your website or so. http://pan.baidu.com/s/1hBRh8 brought it from ebay, though I downloaded the Liberty FSM from here, hope it will help the others. (I'm not sure this link will work in US, no harm to try.)

And one more question, I found the GE point on the back of the engine, however, I found only one wire that link the battery and the point, I can tell from the wire, it is a big one, But not the kind in the FSM which looks tiny, more like the ones in other ground points. I guess the engine is grounded, but this ground is not shared with the sensors, so I need to find this sensor/ecu ground line, right? If so, and if I can not find this wire, can I go some alternative route, maybe from those ground pin of the sensors(TPS, Water Temp Sensor, etc.) then connect it to the GE point with an added wire? Will that work?

[Legacy777]

Thank you very much. I've cleaned all the ground points in the engine bay today, and add a redundant wire between chassis and the terminal. Thus now I test the resistor between each points is close to 0 ohm, even with the metal part in the cabin, This give me more voltage on the cigarette lighter port from 12.8 V to 13.6V while the voltage on the battery is about 14V, with engine running. I will do a grounding kit later on. But according to the multimeter result, the grounding problem is gone.

I tested the HVAC control unit, it is all good, compressor will react with AC button, AC clutch can be heard with the button pushed.

Glad to hear cleaning the grounds appears to have helped.

Now I still have this problem, Both of the fans running, in their fastest speed I guess, while the key is turned to ON.
It is hard to start, due to that the fans take too much energy from battery while starting. This morning, I can't start at all, thus I take out all four AC relays in the fuse box, thus the fan will run much slower then I can start. After driving for like 3 km, I pulled over and installed all the relays back in case of overheating. I can't know the exact temperature of the engine due to that the temp gauge is still not right, it will point to a much lower position.

Further more, I think the ECU is reading wrong temp because when I start the car cold, the idle will drop to 750-800 very fast like it is already warm.

I guess the temp gauge will be right after the fan problem is solved, hope so at least.

Any more thoughts please?

In case you didn't know, there are two coolant temp sensors on these cars. One is for the ECU and one is for the dash gauge. The two-wire coolant temp sensor goes to the ECU, while the single wire temp sensor goes to the dash. The ECU coolant temp sensor can cause the fans to be running when they shouldn't be. So this symptom along with low idle may indicate that the ECU coolant temp sensor should be replaced.

Here's another thing to try with the cooling fans. The way the cooling fan circuit is setup is that the fans will run on high when pressure in the AC system gets above a certain point. The pressure switch for the AC system is in the receiver drier (aluminum cylinder looking thing on the left strut tower when looking at the engine from in front of the car). With the HVAC system off, key in the ON position and fans running, try disconnecting the electrical connector from the pressure switch on the receiver drier. If the fans stop the pressure in the AC system may be too high or the pressure switch may be bad.

If disconnecting the AC pressure switch connector doesn't do anything for fans, then I'd definitely suggest replacing the ECU coolant temp sensor.

[Legacy777]

Legacy777, I really appreciate your work here, I've been download all kinds of documents in this forum and from your website. I want to contribute too, kindly please download this 92-94 legacy FSM maybe you could put it onto your website or so. http://pan.baidu.com/s/1hBRh8 brought it from ebay, though I downloaded the Liberty FSM from here, hope it will help the others. (I'm not sure this link will work in US, no harm to try.)

And one more question, I found the GE point on the back of the engine, however, I found only one wire that link the battery and the point, I can tell from the wire, it is a big one, But not the kind in the FSM which looks tiny, more like the ones in other ground points. I guess the engine is grounded, but this ground is not shared with the sensors, so I need to find this sensor/ecu ground line, right? If so, and if I can not find this wire, can I go some alternative route, maybe from those ground pin of the sensors(TPS, Water Temp Sensor, etc.) then connect it to the GE point with an added wire? Will that work?

You're welcome for the help and thanks for the link to the FSM. I've started downloading it, it timed out, but I'll try again.

You've found, in my opinion one of the weak links in the grounding system. The ECU and all the sensors ground through that point on the back of the intake manifold. The engine and transmission ground through large wire that comes from the battery to the starter. While this should provide adequate grounding, if bolts or main ground wire become corroded then it could cause a lot of issues.

Did you check the resistance of this main ground wire?

What I would recommend is checking the resistance of the main ground wire from the battery to the starter. If this checks out ok, then I would suggest just running an additional ground lead from the negative terminal of the battery to the ECU & sensor ground point on the back of the intake manifold.

I ended up doing that very thing on my car and also ran an additional ground lead to the starter and to the chassis to ensure those main connections were good.

[vincentwl]

Legacy777, I really appreciate your work here, I've been download all kinds of documents in this forum and from your website. I want to contribute too, kindly please download this 92-94 legacy FSM maybe you could put it onto your website or so. http://pan.baidu.com/s/1hBRh8 brought it from ebay, though I downloaded the Liberty FSM from here, hope it will help the others. (I'm not sure this link will work in US, no harm to try.)

And one more question, I found the GE point on the back of the engine, however, I found only one wire that link the battery and the point, I can tell from the wire, it is a big one, But not the kind in the FSM which looks tiny, more like the ones in other ground points. I guess the engine is grounded, but this ground is not shared with the sensors, so I need to find this sensor/ecu ground line, right? If so, and if I can not find this wire, can I go some alternative route, maybe from those ground pin of the sensors(TPS, Water Temp Sensor, etc.) then connect it to the GE point with an added wire? Will that work?

You're welcome for the help and thanks for the link to the FSM. I've started downloading it, it timed out, but I'll try again.

You've found, in my opinion one of the weak links in the grounding system. The ECU and all the sensors ground through that point on the back of the intake manifold. The engine and transmission ground through large wire that comes from the battery to the starter. While this should provide adequate grounding, if bolts or main ground wire become corroded then it could cause a lot of issues.

Did you check the resistance of this main ground wire?

What I would recommend is checking the resistance of the main ground wire from the battery to the starter. If this checks out ok, then I would suggest just running an additional ground lead from the negative terminal of the battery to the ECU & sensor ground point on the back of the intake manifold.

I ended up doing that very thing on my car and also ran an additional ground lead to the starter and to the chassis to ensure those main connections were good.

Thank you very much. The problem has been solved.

Today, I check the AC High Pressure Switch you mentioned and no change. But I noticed that the car's idle drop to 750-800 in the beginning thus I think the ECU is reading a wrong water temperature. I went to the factory and then pull out the ECU and then checked the wire of the fan, the fan run with the pin is grounded. Then the two pins link the temp sensor is checked, it seems that the wire is open. Thus all the wires between the temp sensor(E10) and the ECU(B106) has been checked with a multimeter, then found out that the B46 connector is the source of the problem. Now everything is good. The temp gauge is back as well!

I will do a grounding mod anyway. Then I will fix the fuel gauge and the empty lamp. After that I will have all the gauge in the cluster working fine! Yeah!

Though now I have two problems in driving, I am not sure where they come from:

a. sometimes the car hesitates when the rev come to 2000-2200 maybe. I've changed spark plug, plug wire, and coil pack not long ago(10k before.). Plus the grounding is fixed. Then I was guessing the injector. However I have used several types of cleaner that adds into the gas, the problem is still there.

b. The noise that comes from left front wire side, when I turn right(even very little turn) in a speed faster than 60km/h or when it comes to 60km/h and 80-85km/h when driving in straight. In a long left turning road, driving in 80km/h will have significantly small noise, the noise will come back when the bending road ends(I will go straight or turn right.) It also happens when I overtaking from the left lane, the noise will be very loud when I turn right to steady the car in the left lane. I am guessing the bear? or the CV joint?

[Legacy777]

Glad to hear that issue was fixed.

Have you reset the ECU? I would suggest doing that now that you've fixed the wiring/gauge issue. You can either disconnect the negative terminal of the battery for about an hour or remove fuse 14 (back up power supply for the ECU & TCU) for about an hour.

Regarding the noise, can you start a new thread in the appropriate forum. Any chance you could take a video or a sound clip for us to hear?

[vincentwl]

Glad to hear that issue was fixed.

Have you reset the ECU? I would suggest doing that now that you've fixed the wiring/gauge issue. You can either disconnect the negative terminal of the battery for about an hour or remove fuse 14 (back up power supply for the ECU & TCU) for about an hour.

Regarding the noise, can you start a new thread in the appropriate forum. Any chance you could take a video or a sound clip for us to hear?

Thank you. I will repost the axle problem on another forum if the factory can't figure it out.

After reading your reply, I went to check that fuse #14, and found out the fuse is broken, not sure for how long time. What will it affect the ECU if the fuse is open all the time?

[Legacy777]

With fuse 14 blown the ECU & TCU memory will be reset each time you turn the car off. It shouldn't have any negative affects, but with time the ECU learns and can improve performance/drivability.

Have you tried putting a new fuse in? If so, does it blow again?

[vincentwl]

With fuse 14 blown the ECU & TCU memory will be reset each time you turn the car off. It shouldn't have any negative affects, but with time the ECU learns and can improve performance/drivability.

Have you tried putting a new fuse in? If so, does it blow again?

Thank you very much. The car was idling in 1k rpm before I installed the new fuse in. Idle dropped to 750 as soon as the fuse is plugged in. For several hours till now, the fuse is fine.

However I won't say that the car is driving better with the fuse in, maybe more time will be needed to see effects. I'm thinking that is because I don't have an O2 sensor on the car. There should be one, but the catalyst had broken before, and the previous owner put on a catalyst from another car, thus the port of the O2 sensor is gone. I'm not sure how this will effect the drivability of the car. Any thoughts please?

[Legacy777]

Glad to hear the fuse helped the idle.

Yes, you need to have the O2 sensor in there to help fine tune the air fuel mixture and improve drivability.