Radiator Fans not working.

[brittcrowell]

I've become the mechanic for my sisters 2006 Quest.
Started out as an over heating issue the other week.
I ordered new fan assembly and replaced them.
They still didn't work even when then AC is turned on.
Checked the fuses next to the battery, they are good.
Removed the 3 relays on the power fuse block by the coolant tank and switched them around, still no luck.
Took out one relay and hooked it up to a 12v source and it worked as it should and tested it with an ohm meter.
Shorted across the terminals in the fuse/relay block and the fans ran.
I read on another forum that it could be the ECU/ECM.
Disconnected the two connectors to the ECU and didn't see any corrosion or anything, sprayed it down with contact cleaner and reseated them.
Still no fans even with the AC turned on.
So is it time to get a used ECU?
Any thing else I can check?
Which relay is the one for the AC so I could check if there is a signal coming from the ECU? (I'm guessing there is not)
I could test the other two relays, but I doubt thats the problem.
Connected generic OBDII scanner last night and watched the temp climb to or 160 degrees and the fans still didn't turn on.

Any more trouble shooting I can do before buying a ECU to put in it?

Thanks
Britt

[frapjap]

Howdy Britt, welcome to NICO!

Thats nice of you to help our your sister. I'm not all to familiar with the Quest, but some other things you might want to take a look at before biting the bullet on an ECU that may not fix the issue are:
- those other two relays. Make sure they work.
- grounds. Inspect and clean all of them.
- coolant temperature sensor. Might be dead and not sending a signal to turn the fans on.

I'd start there and see what you find.
Here at NICO we also have a plethora of Factory Service Manuals for Nissan and Infiniti vehicles available at no charge to members. You might want to take a peek at the one for your '06 Quest and see if you can trace the diagnostic steps.
http://www.nicoclub.com/archives/nissan ... nuals.html

If you still have trouble later down the road, you might want to hard wire the fans to come on with the engine, or, wire in a switch if you feel your sister can remember to turn it on and off each day.