Maximeltman

iTrader: (11)

anyone experience this problem? I replaced all radiator fan relays and that didn't do anything. The car also stumbles periodically and the AFR goes very rich about 9:1, any ideas? I read the ects but that would only turn the fans on when the engine running right?

DennisMik

iTrader: (2)

Wrong. When you turn the ignition to the ON position, every system in the car has power applied to it. So if the ECU thinks the engine coolant temperature is 203º F or higher or that the a/c is on, it will turn on the radiator fans.

Maybe the ECTS (Engine Coolant Temperature Sensor) is bad. Connect an OBD code reader that can display live data and see what the ECTS is reporting to the ECU.

Maxima 97 SE

The fans only come on when the engine is off but the ignition is on when the car is leaking coolant and is overheating or when it has no or is low on coolant.

Maximeltman

iTrader: (11)

Idk. I'll start w the ects. Maxima 97 se I can't really understand you though.
The fans start when ig is 'on' position. Would this be the reason it's randomly enriching and stalling? or should I try grounding the maf sensor a little better? This whole harness isnt from my car it was salvaged at a junkyard and modified a bit to use and it hasn't had this problem till this week.

DennisMik

iTrader: (2)

If the car had been working ok with that harness for some amount of time, I would think that it was modded ok. Something has changed, i.e., gone bad. I have no idea if it is the harness or not.

FWIW, I went and tried my 2000 without starting the engine. The engine coolant temperature was 173º so the fans wouldn't run based on temperature. When I pressed the a/c on button, the fans didn't come on. So the engine does need to be running for the fans to run in regards to the a/c. If I have the time, I'll disable the fans and start the car and let the engine work its up towards overheating. Then I'll shut it off and reconnect the fans and see what happens then I turn the ignition on.

Maximeltman

iTrader: (11)

Yea thank you dennis. The harness was indeed modded, by me. It's a 98 mt harness that I had to put into a 99 mt... I had to re-route quite a few wires here and there. But as I said it just started happening recently and was fine for about a month or so.

Maxima 97 SE

I was trying to say that the only reason why you fans wont turn off when the is not running is because your car is overheating for some reason which is why your fans are still running even though the engine is not. This could be from things like low coolant, leaking coolant or even no coolant in the engine. This had happened to me and it turned out that I was leaking coolant to the point that I had barely any coolant left which made the fans still run even though the engine was off because your car was overheating. This is a warning and safe mode feature to let the driver know that there is something wrong with the car.

Maximeltman

iTrader: (11)

No the fans turn on even after waiting overnight, engine off. So on a totally cool engine they still cut on when I turn the key all the way less starting car. My coolant level is good and no loss. coolant is also clear, no oil in it.

Maxima 97 SE

Then it's a bad coolant temperature sensor or faulty wiring. I once broke my wiring harness that connects to the sensor and the wire was really brittle and it snapped and from that point on the fans would not turn off no matter what the temperature was even if the engine was cold. Every time I would put the key in the on position they would turn on and would never turn off even when driving the car. So check that. Plus I had a check engine light and a super high idle because the ecu thought that the car was still cold which made it run super rich. After I replaced the harness it was all good. But if you have never replaced your sensor it could have internally rusted and have gone bad overtime.

DennisMik

iTrader: (2)

Maybe your ECTS is wacked. When the engine is cold, either hook up an OBD reader that can display the coolant temperature or measure the resistance of the ECTS.

At 70ºF (20ºC), the resistance should be between 2.1K to 2.9K ohms.
At 200ºF (93ºC), the resistance should be between 235 to 260 ohms.

See page EC-125 of the 1996 Nissan FSM.
http://boredmder.com/FSMs/Nissan/Maxima/1996/EC.pdf

If the ECTS has a low resistance, this is telling the ECU to run the fans even though the engine isn't really overheating.

Maximeltman

iTrader: (11)

Thanks both of you guys.
I re-grounded the MAF (junkyard find due to my original one melting) and that seems to have stopped the rich AFR and stalling issue.
Maxima97se, I already checked the wiring a few days ago to the ECTS and it was good, ground to - battery was good and 4.8v with IGN on on the hot wire.
Dennis-I did the resistance check and cold it was about 1.8kohm, when hot it was about 260 ohms, so I don't think it's the sensor, but since everything else checks out I will replace it anyway just to eliminate the possibility.
Any thoughts on alternator strain from fans running all the time?

DennisMik

iTrader: (2)

The alternator will be fine. When you drive with the a/c on, the fans will be on all the time. The alternator can handle everything in the car being on at the same time.

Speaking of a/c, there is a connection from the a/c triple pressure switch to the cooling fans, which would be used in case of certain malfunctions of the a/c. If this switch is shorted, the fans would run all the time. If you unplug the wire harness from this switch, that would stop the fans if the switch is causing the problem.

But this switch is in a tough spot to get to. If you look down the driver's side of the radiator, you will see some silver a/c tubing. You will see a metal cylinder maybe half the size of a beer can with wires going to it. Unplug this connector.

Should this pressure switch be the problem, you could drive the car with it unplugged, but I don't know if the a/c would work or not.

Maximeltman

iTrader: (11)

Yes. That switch was totally melted in the fire, I broke it off, exposing the pins on that ac dryer. I had the connector unplugged and plugged and that might have something to do with it I hope, but I havent played around with it enough because, as you said, it is a tough spot to get to, especially when you don't have the other half of the connector to at least guide you to the correct connection orientation.

DennisMik

iTrader: (2)

I should have mentioned this with my post about the triple pressure switch.

The radiator fans are 2 speed. So there are 2 circuits for them, one that tells them low speed and one for high speed. The electrical supply to the fans is similarly split. There is a fuse for the low speed side and another fuse for the high speed side.

The triple pressure switch will turn on the high speed side of the cooling fans. So if the pressure switch is the problem, pulling out the high speed fuse would stop the fans. The fuses are in the box by the battery.

RAD FAN 1 fuse is for the low speed side of the fans.
RAD FAN 2 fuse is for the high speed side of the fans.

If you pull the RAD FAN 2 fuse and the fans stop, you can continue with pulling the wires off of the triple pressure switch. If the fans don't stop, then we are barking up the wrong tree.

Maximeltman

iTrader: (11)

I just cannot figure this. Even after regrounding the MAF, it still occasionally bogs, stalls, gets really rich AFR.
The radiator fans still come on engine cold, IGN on.
It still has great power when it runs right, but it's a little annoying.

Maxima 97 SE

Replace your engine coolant temperature sensor with a new one. It gets rusted and breaks and also control air fuel ratio plus the fans.

DennisMik

iTrader: (2)

Did you ever pull the wires off of the triple pressure switch?

What you need to do is figure out if the fans are running on low speed or high speed. Easy to do. Start by removing both the RAD FAN 1 & RAD FAN 12 fuses. Then put in the RAD FAN 1 fuse and see what happens. Remove the RAD FAN 1 fuse and put in RAD FAN 2 fuse. The reason for starting the test with both fuses out is that if both speeds of the fan are running, you would not necessarily know that that the one speed stopped when you pulled the first fuse.

RAD FAN 1 fuse is for the low speed side of the fans.
RAD FAN 2 fuse is for the high speed side of the fans.

Based on what speed is running will allow us to do some specific wire testing/tracing.

Maximeltman

iTrader: (11)

I will take pics and show you what the switch looks like, I know the cylindrical part broke off, but I can still connect it.
I know both hi/low speeds on the fans work because I pulled the brown and blue relays and confirmed this, but where are the fuses you speak of located?

DennisMik

iTrader: (2)

The RAD FAN 1 and RAD FAN 2 fuses are in the fuse box by the battery. Wasn't it your car that the battery exploded/burned on? If so, do you have said fuse box by the battery?

Maximeltman

iTrader: (11)

Dennis, Yes.. But that fuse box was replaced along with the rest of the harness with a junkyard one, and all the fuses are good. And for a month or so after I installed the J/Y harness the fans would only cut one when at idle, engine warm. Something weird has happened. I even swapped the ecu with a diferent one and the same thing happens, so I think that it's not an ecu problem.
old:

"new":

Maximeltman

iTrader: (11)

On a cold engine the ects tested 1.8-1.9 kohm and isnt that low impedence? That's like it should be at around 140 degree farenhheit

DennisMik

iTrader: (2)

1.8K ohm is an OK reading. The chart in the FSM is hard to read, but to me, 1.8K ohm looks like it indicates maybe 80-85ºF.

The resistance of the ECTS goes down as the coolant gets hotter. At 32ºF (freezing) it looks like the resistance should be about 4K ohms, while 212ºF (boiling) looks like it would be around 200 ohms. Since the fans are supposed to come on at 203ºF, that would make the resistance of the ECTS about 250 ohms. So I don't think the ECTS is your problem.

As another point, some people have said that the fans won't come on unless the engine is running. I don't know if this is true, but I lean towards agreeing with it, because on a similar note, on my car I have turned the ignition switch to ON without starting the engine and pressed the the a/c on button and the fans did not run.

Having an ECU to swap is a bonus. Since the problem did not go away, we can rule out the ECU.

So I'm still curious as to whether the fans are running on low or high speed or possibly both. That is what my fuse pulling post (see # 17 above) is all about.

I'm not sure I understand you when you say "would only cut one when at idle". Are you saying that one fan would stay running when the other one stopped? That could only happen with the high speed side.

Need to determine which fan speed is active so appropriate circuit can be checked.
Is the wire that energizes the relay shorted to ground?
Is something touching the bottom of the fan relay sockets, jumpering power?
Is the triple pressure switch shorted or the wires touching?

Maximeltman

iTrader: (11)

I'm saying that when at idle, the fans used to cut on normally like when engine temp gets high enough. They weren't on all the time like they are meow. This is kinda frustrating, I will make an attempt at your diagnosis later today and report back..

Maximeltman

iTrader: (11)

Dennis-The fans are running on high speed. When I pulled radiator fan fuse 2 they both completely shut down, when I pulled radiator fan fuse 1 it didn't do anything, both fuses are good. When I just had radiator fan fuse 1 installed, the fans did nothing. So it's stuck on high speed. I've known this since the beginning when I pulled the relays but I must not have read your post clear enough. Did I mention that the top part of the dryer actually melted and snapped off? I just have the switch harness connected directly to the dryer pins.

DennisMik

iTrader: (2)

Yes, you did mention the dryer connector having melted. But if you had posted about the fans running on high speed, you can tell that I missed it.

So now I know what direction to proceed.

If you were to remove either Fan Relay 2 or Fan Relay 3 and check continuity of pin 2 in the relay socket to chassis ground (with the car shut off), I think you will find continuity. This is not what what you want, because continuity equals short. Pin 2 being grounded causes the relay to energize and send power to the fan motor.

In normal operation, the ECU will energize the relays and while there is the switch on the a/c dryer, it is not part of everyday, normal operation. But it is there and can cause the fans to run on high speed. However, the continuity check on the relay does not tell you where the short is.

You could check if the ECU itself is shorted internally by removing the big connector on the ECU and doing the continuity test again. I hope you still have continuity to ground on pin 2 instead of a bad ECU.

Now you will have to get at the dryer switch. Either carefully inspect the wires to see if they are touching. You can also try unplugging what is left of the connector if that is possible or remove one of the 2 wires that are for the fans. The wires for the fan are pin 2, solid black to chassis ground and pin 3, light green to Fan Relay 2 and Fan Relay 3. These 2 wires are diagonal from each other in the connector.

So once you disconnect something, somehow from the dryer switch, do the continuity check again. I hope you do not have continuity, because further troubleshooting will be much nastier.

I don't know how the wires actually are routed, so finding a short becomes more difficult. Plus when you spliced in the 98 harness, you probably spliced the wire from the ECU. Could this splice be somehow touching something? This is why it would be difficult.

Maximeltman

iTrader: (11)

I don't have continuity to ground from pins 2 on either relays just pins 1, and Pins 2 have positive battery continuity.

I just saw that continuity exists between light green and black wires on the pressure switch. And these two wires both have continuity with relay 1 pin 5, and relays 2 & 3 pins 1 3 5 &7.
If I pull fuse 17 under the steering wheel fuse panel, the fans are disabled, and that is the green/yellow wire.
Thanks alot for ur time Dennis

DennisMik

iTrader: (2)

That is not right, at least if the FSM is correct. I have encountered errors before and this may be another one of them.

If the FSM has pin numbers 1 & 2 reversed, then what you are saying makes sense IF you also had the ignition key in the ON position.

Going by the FSM, pin 1 of the relay is connected to fuse # 17 in the dashboard fuse panel. This fuse will only have power when the ignition switch is in the on position.

Pin 2 of the relay gets connected to ground by the ECU, which causes the relay to energize and connect power from the RAD FAN fuses to the fan motors.

How did you determine which pin was 1? Did you go by numbers in the relay socket or on the bottom of the relay? If you went by the bottom of the relay, that is a reversed, mirror image of the socket.

The part of finding 12 volts on the other pin is only valid when the ignition switch is in the ON position. But pin 3 of the relay does have 12 volts on it, coming from the RAD FAN fuse.

If you look on page 6 in this link, it shows the bottom of the relay and the pin numbers. Look at the 2nd one from the top that has 2M on the left side.
http://boredmder.com/FSMs/Nissan/Maxima/1999/EL.pdf

Could you double check this? This is throwing me for a loop since I can't put my hot grubby paws on it...

Maximeltman

iTrader: (11)

Went by the numbers on the relay.

2m is like the normally open brown relays (rad 2 & 3) that I also tested for functionality by applying voltage to them, I actually tested all the relays and they're all in good shape..

Does the dryer switch have a certain way of connecting? I'm wondering if since the cylider-shaped part of the switch snapped off and I just plugged the harness onto it, if that did something but all of the fuses are ok.

DennisMik

iTrader: (2)

Those are the relays I was talking about. I am not questioning the relay itself, I believe they are good. I am questioning the wiring, has a short happened/

I'm sure all the fuses are OK because the fans wouldn't be running if you had a blown fuse.

While you don't have the plastic on the dryer switch, I am assuming you plugged the wires on correctly as you did not have the problem right after you did the harness repair. The thing I wondered about is if the wires in the harness don't have any insulation on them, could the wires have come in contact with each other, and could the pins in the dryer switch be touching?

Back on 8-22 you said you pulled fuses to verify that it was the high speed side of the fans running. High speed uses the RAD FAN 1 and RAD FAN 2 relays. Since the relays are good, that tells me that both relays are energized and sending power to the fan motors. Pins 1 and 2 of the relay are the energizing coil for the relay.

According to the FSM, pin 1 will have 12 volts on it anytime the ignition switch is in the ON position. Then pin 2 gets connected to ground by the ECU when the fan is supposed to run.

So I am thinking that the pin 2 wire is shorted to ground. But then you posted that you found 12 volts on pin 2. If you have a short on pin 2 and the schematic in the FSM is correct, this cannot be. Similarly, if you had the ignition switch in the OFF position, this should not be, even on a properly working car.

So the thought has entered my mind that you may not have done what you thought you were doing. For one thing, I asked you to measure continuity and you came back and said that you had voltage on the pin. For continuity, you set the meter to ohms, which is for measuring resistance. A short is zero ohms or no resistance. When a meter is on ohms, it will not show volts.

But I also mentioned about mixing up the pin numbers, using the term mirror-image. It depends on how you hod the relay after you have unplugged it. Here is a photo of the M2 relay and its socket. The numbers in the photo are pin numbers.

Maximeltman

iTrader: (11)

OK so yes pin 2 is continuous with ground. I had them reversed. I hope you don't think I'm a complete idiot but I do make mistakes.
I had to hack the two main connections by the battery (the most part of modification) to make the 98mt 'engine room harness' harness work with the 99mt engine harness, here is a pic. I basically had to remove the two main brown/black pigtail connectors from the burned 99 engine room harness by the fusible link, and solder them to the 98. I traced all the wires the best I could to be sure they were the same wires and for the most part they are. I think that's where the short is happening, but I can't be sure.


The other pink wire as seen in this pic was an audio wire iirc:

Here's a pic of the original burned harness just for fun since I didn't know I had it was a pain to trace the wires

So I guess it would be easy to mess this up somewhere.
Where do I go from here?
Oh and I still had continuity to ground with the ecu disconnected and you said that was a good thing. I hope it is.

DennisMik

iTrader: (2)

Absolutely not. When you have been beating your head against a wall with a problem that refuses to be fixed, you get burned out and will probably make a mistake (or two) somewhere along the line. I understand that because I've been there, done that, bought the t-shirt. I'm running out of storage space for all those t-shirts.

When I saw your thread from when the battery exploded and looked at those photos, I don't know if I would have even attempted to try and fix the car. But you did attempt it and you got the car running again. Hell of a job, I'm impressed.

But now this fan problem has popped up. Don't give up now. If it is related to having fixed the battery fire, consider the repair 99.999% done. Just one last little detail to go.

It is good from the wallet's perspective because you don't have to replace or send the ECU out for repair. I have this thing about replacing the ECU. From the point of fixing the fan problem, it would have been an easy labor resolution.

With a short in the wiring somewhere, there is no written information that will allow you to pinpoint the trouble spot. Finding and fixing a short requires patience and logical thinking so that you can come up with a best guess as to where to look. And I do mean guess. But the logical thinking means that you will get lucky and guess correctly.

I'm still thinking of two areas to check for starters. The a/c dryer switch and the harness splices.

On the a/c dryer, I think you have said that the wire harness connector got replaced with the 98 harness. So probably the wire harness is OK. But the switch on the dryer has a melted connector. Maybe the switch itself is shorted internally. Unplugging the wires from it will prove or rule out this possibility.

Now for the nasty part - the wire harness splices. This will be time consuming. How did you insulate the solder connections? If you used electrical tape, it could have come undone and even slipped off. So all these wire splices need to be examined. The only thing that makes it somewhat easier is that you are looking for a light green wire.

You might want to consider buying a test light if you don't have one. It makes this kind of a job a little easier. As the name implies, there is a light in the unit. If you touch one end to the battery positive and the other end to ground, the light inside will light up. In your situation, you would connect one end to the battery positive and the other end to pin 2 of either RAD FAN 2 or RAD FAN 3 relay. It doesn't matter which one.

Right now there is a short on the light green wire that connects to pin 2, so the test light will light up. As you work, all you have to do is look at the light. You don't have to stop to read the ohmmeter after you have done something. If the light is still on, you have to keep working. When the light goes off, you have hit the jackpot.

You can get test lights at any auto parts store, many hardware stores, Harbor Freight, Sears, etc. Prices will vary of course, but I wouldn't pay more than $10. All a test light is, is a light bulb with 2 wires on it. You could even make your own. Some do have a battery in them. These let you use them in spots where the car battery is too inconvenient to get to and on other devices besides a car that don't have a battery. You could use this if you wanted to, you just don't connect it to the battery.

Maximeltman

iTrader: (11)

Thank you Dennis are you a nissan mechanic or something you been like a big steel life raft in a sea of great white sharks.

I'll be working at this from here on out and try to make, if not buy a test light for the task at hand

On a side note, I noticed that my white/red wire on the TPS sensor was broken, looked like a clean cut, so I soldered that back together and the stalling, rich/lean afr seems to have disappeared for now. So I'm pretty stoked about that! As long as that issue is resolved, that rules out anything to do with the fans always on, but I'm still going to attempt to get that fixed I already ordered a trip pressure switch from ebay for 10 shipped it's not calsonic but it's better than what's on there now.

DennisMik

iTrader: (2)

You are welcome and thanks for the kind words.

I'm not a mechanic. I was at one time. I tried it but I didn't like the grease part of being a grease monkey. It people would keep the engines clean, I might have stuck with it. But cars gave me an introduction to electronics and I ended up being an electronics tech.

Fixing something mechanical and fixing something electrical take the same mindset. The difference is that with mechanical repairs, you can see and touch things that move and line up, where in electronics, you have to visualize things in your head. Diagnosing a problem is the same. You have to know what is supposed to be happening and then figure out why it isn't.

What you have to do now is the tedious, boring, unglamorous and time consuming part of electronics. Just stick with it and you will get it done.

Maximeltman

iTrader: (11)

Dennis I found out the problem! It was a short in the fusible link junction when I pull it towards the driver side fender, the fans shut off, when I release it, they come back on, so I wedged an allen wrench by the battery to force it towards the fender and I watched the fans with engine running, and the fans cut on and off like normal. So I took the fusible link apart and unwrapped the wires, re-wrapped them more loosely, and it works now. I haven't put the other lower half of the fusible link casing back on yet but it should be good without it.

DennisMik

iTrader: (2)

EXCELLENT! Go treat yourself to a nice cold beverage of your choice. Or two or three...

That casing as you call it is there to protect the wires from the elements, rain and whatever. I believe you should put it on, but it may not really matter.

Your perseverance paid off and you ficed it. EXCELLENT. Good job.