I had a problem with my 2004 G35 sedan with about 65k miles, and I finally got it figured out and I wanted to share what happened with the community so it is searchable if anyone has similar problems. I gather from doing some internet searches that the fans are a common problem area with these cars so it's not surprising mine went out.

The initial problem I noticed was that when I would get in the car on a hot day, the air conditioning wouldn't work at all until you got up over 30 mph or so. Once you got going 30 mph or so the air conditioning would work no problem whether you were stopped or not. These symptoms didn't happen all the time, but seemed to get more common as time went on.

I had assumed that the expansion valve was acting up so I had ordered parts to fix it. Luckily, before I ripped the dash off and started doing major surgery on the A/C system, I was sitting at a drive thru and noticed the temperature gauge was getting hot. As I pulled around the building I shut the car off and right as I lifted the hood up to have a look, the overflow bottle was starting to fill up and boil over. Once it cooled, I started the car and noticed that the fans didn't come on and I realized that was the root cause of my A/C problems as well.

I pulled the fans and shroud out of the car and bench tested them with some jumper wires and a spare battery and they turned when I applied voltage to them. Sometimes when I would apply voltage they wouldn't turn. It was like there was a dead spot where if the fan was stopped in a certain position, they wouldn't start up, but in most positions they would.

I finally reasoned out what was going on....... There were dead spots where the fan wouldn't start up, but once they were turning, the momentum of the fan would make it skip over these dead spots and the fans would work fine, but if the fan happened to stop on a dead spot, it wouldn't start up with voltage alone. When this would happen and I would start driving, once I got over a certain speed, the airflow from driving would windmill the fans off the dead spot and they would start turning electrically again which explains why they wouldn't work from a cold start, but would work even at a standstill once you got over a certain speed. Replacement fans from Rock Auto fixed the problem.

I wanted to put this up because the fact that they tested good on the bench the first few times was confusing and made me think I might have another electrical problem which would have been a dead end to try and troubleshoot as the rest of the system was fine. Hopefully if someone searches for these symptoms this will point them in the right direction. Cheers!

 

This is a huge issue with all the G35/350z fans - it's the reason my original engine overheated and blew the head gaskets.

I "fixed" mine by opening the motors, removing the built up brush debris, oiling the brushes, stretching the springs and sanding the brushes down so they don't get stuck again. This helped and I haven't had any overheating issues since. But I have caught them not spinning once after not using the car for a couple weeks.

Basically, the problem is a combination of the motor brushes being "too snug" in the part that holds them, the springs being too weak to force the brushes out and - over time - the buildup of brush dust and other debris making the brushes stick.

We had a 2005 350z with just 27000 miles that was having this issue. It was after a long time of sitting. Also in England it rarely got hot enough that the fans were needed, so when the time came to needing the extra cooling power, the fans motor brushes were already seized.

 

Thanks for the additional info. It never occurred to me to crack open the motors and try to fix them, but good for you for figuring out the root cause of the problem!

 

My "fix" was only really temporary. Even though I use the car pretty much every day one of the fan motors has suddenly started to fail more frequently.

I don't want to mess with over heating so I'm just going to replace both with new units.
Which did you go with and how much were they?

 

Fan motors can be found at rockauto.com for less than $40 each. Example here: https://www.rockauto.com/en/moreinfo...431975&jsn=314

 

I put the TYC 620980 fans from rock auto and they were $87.79 before shipping. They've been in for a few months now and they haven't missed a beat! This part number is the entire fan assembly with the shroud/motors/fans, etc all ready to go. I priced out the motors individually and it was only like $10 cheaper than replacing the whole assembly with a new one so I elected to replace the whole thing. I was concerned that it might not fit, but figured I could always swap the new motors out with my old ones, but it fit just fine and has worked perfectly. I hope that helps!

 

I contemplated swapping out the whole thing as the price difference is negligible.
However I found a pair of fan motors for $65 posted (https://www.1aauto.com/infiniti-g35-...r/i/1arfk00018) and bought these.

The price difference helped sway my decision but also I didn't want to have to drain my coolant to get the top hose off to get the whole fan unit out. From memory I think I can swap the motors out without taking the whole fan assembly off.

 

Good finds gentlemen, looks like the fans only are currently out of stock. I should probably replace them before I sell Amanda. Just don't really want to shell out more money.

 

Wow, surprised they sold out now. I think I bought the second to last one.
I think it's totally worth replacing them. My commute to university is normally pretty brisk with no traffic. But on a hot day in 9am/5pm traffic....watching the temp needle go up is scary.

 

I took the whole fan unit out and while I did take the top radiator hose off the radiator, I only spilled like a cup of coolant which I caught in a small bucket placed under the hose before I removed it. I kind of folded the hose out of the way while I took the fan unit out. It wasn't bad at all and I just topped up the coolant when I was done. There's no need to completely drain the coolant just to take the top hose off.

 

Same parts for a 04 coupe?

 

I think so but not positive. Click on the link and backtrack to enter the coupe info.

 

Thanks man. It does work for both models. Pic for reference.

 

Mine is currently having the dead spot issues very weird.

Overheated yesterday when pulling into the parking garage.

Can we just talk about that high quality coolant overflow? It's literally just an open spot in the overflow tank. I had hot coolant shooting at the headlights. Good thing they were sealed up well.

I'm going to order the TYC and some Nissan OEM coolant. Thanks for posting this thread helped me come to my fix.

 

I replaced the whole assembly on my 06 a couple weeks ago. My fans only ran at the low setting or one would not spin at all. It was just under 100 bucks for the whole assembly, i went that route instead of just doing the motors. I only drained a small amount of coolant out, so i could get the top hose out. Had to loosen the ac lines to help slide it out and it took less than am hour.