Mikeyk9

What's up guys.... So I have a 5th gen 5spd that I've owned for almost 2 years and 40k miles. Every time I do research this forum pops up and I like what I see so I joined it. I've done a fair amount of work to my baby and most of it myself.... She's flat black with dual exhaust with cherry bomb glass packs.... She sounds great! So my problem is this..... I recently had a starting problem due to a damaged front CPS replaced it and fixed that problem but the next day my starter burned out from the extra strain prior to the CPS being replaced so I put a starter in.... So now as I sit in the hot sun waiting for someone I turned on my A/C only to find that the compressor wasn't kicking on. I've had a small coolant leak from the radiator for a while but the A/C always cranked since putting in a new compressor so what I saw when I open the hood was that my cooling fans weren't kicking on anymore and I was starting to overheat. I've checked the fuses, made sure all the wires are plugged in properly and I'm assuming that I would have had to have all 3 relays crap out at the same time for neither fan to kick on on low or high speed. I've also checked the CTS and that is also functional..... Any ideas? While I did have to move the main wiring harness out of the way of my starter I did not have to put any serious pressure on it. I also did not disconnect the battery right away and got a quick tiny spark but I'm figuring if I fried the computer there would be many more problems if the car would even start in the first place.....

Thrillho

If it's too hot then your low side pressure might get too high for the AC compressor to kick in, in which case I'd getting a screwdriver and bleeding off a bit of pressure until the compressor kicks in.

If your fans are not kicking in then you'd feel the heat from the firewall. I was messing with the car earlier and I didn't push in a connector in properly and went for a ride, it felt like I had the heat on at full blast + the steering wheel got hot. Couldn't blame that on the weather because it was night and very mild out. If you felt that then I'd suggest checking the connectors, especially up front near the air intake.

If you changed your starter then you should probably do the alt as well. Check your voltmeter to see if you lose any voltage. Should be at 12.2-12.5 under no load. Anything less than that and your alt sucks.

Mikeyk9

So I didn't have an a/c problem till the fans quit on me. Today I tested them by wiring them directly to the battery and the both work. I checked one of the 3 relays and it was working properly. I left the fans wired up and on and went for a ride. It took a while, about 30 or 40 miles on back roads but it eventually overheated and started stalling at stop signs so I stopped and let it cool down before topping off the water. The reservoir was still full but the radiator was quite low. I'll try replacing the thermostat tomorrow and the radiator Wednesday but that still won't fix my fan issue.....

DennisMik

iTrader: (2)

Do the fans turn on for normal driving? The way you explain the problem has me a little confused, but your second post seems to say the fans don't run at all.

Each radiator fan has its own fuse. They are under the hood by the battery. The cover labels them RAD FAN 1 and RAD FAN 2. RAD FAN 1 is the fan motor closest to the battery. It would be very unusual to have good fan motors and blow these fuses.

Inside the car in the fuse panel is a 20 amp fuse that powers all 3 fan relays. It is fuse # 20, labeled ENGINE CONTROL. It is the middle column, top fuse. It supplies power to more than just the radiator fans, but swap it out. I said swap it out because these little fuses can still look good when they are bad.

This has nothing to do with the radiator fans - There is a 10 amp fuse for the a/c compressor clutch coil. It is under the hood and is labeled AIR CON.

If you can't find a bad fuse, we're going to have to break out the voltmeter and start checking things. At that point, I will need to know what year the car is.

Mikeyk9

I swapped out the 10a eng control fuse in the car. Still nothing. That is correct that neither fan is kicking on at all. I checked all the fuses and relays and all seem to be in good working order. I did go buy a multi meter but I'm no pro at electrical things LOL..... It's a 2000 SE 5 spd. I've temporarily wired the fans directly to the battery and they are functional. I'm still overheating but I also still have a leak in the radiator and lose water quickly so I think that is most likely the issue for that. Hopefully replacing the radiator today.

User1

Replace radiator and ECTS. Everything will return to normal.

DennisMik

iTrader: (2)

Definitely get that water leak fixed. Aluminium engines don't fare well to overheating.

For the cooling fans, check the ECTS (engine coolant temperature sensor). This sensor tells the ECU what the coolant temperature is. If the ECTS is bad, it may not be telling the ECU that the water is hot and the ECU doesn't turn the fans on.

To check the ECTS with the voltmeter, locate the ECTS. follow the upper radiator hose back to where it connects to the engine. Several inches after the radiator hose you will see 2 sensors in the metal pipe. The 2nd one back that has 2 wires on it is the ECTS. When the engine is hot (engine does not have to be running for this) unplug the wires from the ECTS. Take the voltmeter and set it to the OHMs scale. Place the 2 meter probes on the ECTS contacts where the wires plug on to. An engine at operating temperature will have a reading of about 240 ohms (or .240 K - depends on how your meter displays) for water temperature around 200º F. A higher ohms reading of perhaps 600, 1K or higher says that the engine coolant is not at operating temperature.

Mikeyk9

I replaced the radiator today and it's maintaining a normal temperature according to the guage in the car and I get a reading of .274 ohms. I have the fans wired to my fuse panel on an ignition fuse so they are on with the key on and off with it off so this fine for a temporary fix but I paid a lot to fix my a/c and without the fans registering as on my compressor doesn't kick on so I would definitely like to find the root of the problem....

Amave

It IS possible you fried the ECU on the radiator fan circuit?

I've seen ECU's be bad inside on the circuit board on the specific circuit. When it sparked , it doesn't take very long to short a circuit. And just so you know the ECU isn't fused except for the several fuses that power it.

This is why bad motor mounts, IACV valves will fry the ecu. No it doesn't fry the whole thing, normally just the circuit that failed .

With your specific problem you are going to have to find out if the ECU is sending the output signal to turn on the radiator fans.

On a normally working vehicle when you start the engine, and the ECU sends and receives signals it monitors the ECT ( Engine coolant temp sensor ) and when the coolant temp is below a specified thereshold, it stays in " open loop " , it ignores all sensor signals except the ECT, MAF ( not sure exactly how Nissan ECU logic is but thats how it is with Honda ) until it reaches a certain temp, usually 100+ degrees ( again not sure about Nissan ECU logic but with Honda it is around 100-120 degrees ) then it goes into " closed loop " , where the ECU monitors all input signals from the sensors ( CKP,CMP,O2 etc. ) , once the thermostat opens and the temperature reaches to 212 degrees ( again not sure what Nissan ECU logic is but with Honda my guess is it's similar ) , the ECU sends out a signal to turn the radiator fans on , if the ECU " sees " the input from the ECT as higher than 212 ( again a guess , see previous disclaimers ) it will not allow the compressor to turn on to keep the loads down , the over flow in the radiator neck releases the added pressure and blows coolant out .


So with your car you have to see if the ECU is sending out the radiator fan signal on command . My guess is Nissan and Honda are the same when it comes to ECU logic so you have to check at the ECU connector for output power to the radiator fans, to do this you will need a DMOV and the electrical portion of the FSM ( you can DL it from NICOCLUB )


Once you find the answer to the specific circuit you will know if the ECU is no good, the wiring harness is no good or if the problem is after the fusebox.


If i had to guess judging by what you posted you probably " opened " the circuit inside the ECU by not disconnecting your battery when you replaced your starter .