Hey all,

I just replaced my A/C condenser on my 96 Max, and now when I turn the car on, the radiator fans are always on (and it sounds like at max!). The dashboard temp gauge is normal, and scan gauge says I am <120C at startup.

I bumped the relay box next to the accumulator/dryer a bunch while installing the condenser...so I think I screwed up one of the relays. Anyone have any similar experience on what to do? From the wiring diagram I'm looking at, there are 3 fan relays...2&3 connect to motors 1&2 respectively, and relay 1 connects to both...so is this the one I likely broke?

Thanks.

 

Isn't the fan supposed to shut off when you speed up to 40 MPH? Are you sure the fan is still on then? IIRC, the fan is always on initially when the car starts.

 

try switching the relay its the easiest and most cost effective to start with, did this occur prior to you bumping the relay or switching the condensor??

 

Is the compressor running? Can you turn it off? With the compressor off, do the fans still run? I wasn't aware of the 40 MPH thing but I do know that anytime the AC is on, those fans are on.

You maybe able to narrow the field some by pulling the relays one at a time and noting the reaction. If the first one you pull doesn't seem to affect anything then replace it and pull the next one and so on.

Assuming everything is hooked up completely and correctly, a likely problem is that one of the relays has welded shut. If something like that happens to me I would take off the relay cover and unstick the contacts and then redress them with some 320 or 400 grit sandpaper followed by a good flushing with electric motor cleaner or even brake cleaner if you have it. Of course people with plenty of money would just replace it with a new one.

 

This is with the A/C off, the whole climate control thing off too. And it didn't shut off after going to 40 mph....as I recall, it didn't used to come on until the water temp went over about 198F.

 

My cars fans stay on after i shut off the car for 2 min. or so. My friends Altima does the same thing though. But isn't that good, because I live in Miami, a.k.a hot as hell, And i had to put more powerful motors so it will keep the car and the tranny cool, pus have the ac at 68* on 100* weather.

 

Did these new fans come with a controller as well?

Stock, the fans should not run after the key has been removed. The fans only get power when the key is in the on position (or start).

 

Recall my old Honda did that too, but not the Maxima. Don't see how it will make much difference anyway as your water pump is no longer moving the water...

 

I have a 97 Max so my FSM pages may vary, but starting on on page EC 340 you will find the diagnostics for P1900 (Overheating), this is where you will find the wiring diagrams for the cooling fan system.

I didn't realise it until I found this diagram that it is a 2 speed fan system. When the AC is turned on the fans should operate at low speed I think but if the Triple Pressure Switch in the AC system is tripped, they will go to high speed.

There's about 10 pages in the section and though you don't have an overheating problem, the diagnosis is effectively the same. You first need to determine if it is running at low speed or high speed (don't guess). If it's running at low speed, pull cooling fan relay 1 and confirm that it shuts them off. If it does, then you will have to determine if the ECM is telling it to come on. If not, then the relay is welded shut. If the ECM is telling the fan to come on then that's a whole different trail to follow.

For high speed operation, it appears that one of each of the remaining 2 relays, controls it's own fan. If pulling relay 1 didn't stop the fans then it's likely running at hi speed. Leave relay 1 out to be sure and then unplug the other two and each fan should stop in turn. The odds of two relays becoming welded at the same time seem pretty remote to me and so it would be more likely that the ECM is telling the relays to close in which case you'll have to follow that diagnostic path.

 

check the wiring/connector to the engine coolant temp sensor (the larger sensor, there are two right next to each other, the small one ONLY gives info to the temp gauge on your dash, the larger one gives info to the ECU). if the wiring to the larger ECTS (the one that provides the ECU information) is broken, the fans will run all the time when the engine is on, because the ECU doesn't know what the real coolant temperature is. This happened to me a few months ago. Fixed the wiring, and the fans go off (and only come on when they are supposed to).

beyond that, I would expect that there are other fault modes which the ECU could go into for other reasons that would also keep the radiator fans on 100% of the time.

 

scan gauge says I am <120C at startup.

If I read this right your scanner is saying your at 120 with a "cold" engine. On some cars, the gauge reads from one sensor, and your ECU reads a another sensor for A/F, timing, and fans. Perhaps your ECU thinks your at operating temp?

 

Let's hope you're <120C at startup since that is almost 250F. It doesn't sound like a useful number.

 

That's running really hot if you ask me, on most domestic cars the temp guage actually says the degrees, and 260F is the highest, so I think you're running really hot, so I would hope its 120F with a cold engine rather than 120C...because that's just insane.

 

FYI - the < arrow means "less than" - it doesn't give an 'actual' temp reading.
You should follow the trouble path described before.