I have an 09 Coupe and bought some Morimoto XB50 bulbs to replace the oem ones, but the oem say 35w on them. I was under the impression coupes had 55w ballasts, but can I run the XB50 on the stock ballasts without any problems or should I try to exchange and get 35s? I haven't actually driven the car yet with the new bulbs.

 

Short answer: you will be better off exchanging for 35W bulbs.

All Nissan/Infiniti OEM ballasts are rated for 35W.

Even if the ignitor had enough juice to start the arc between the electrodes (in the bulb), the ballast likely would not be able to maintain the arc for long. It may work for a while, but in time, as the electrodes in the bulb wear, the ballast would have to work even harder to keep up. Both would burn out considerably faster than a properly matched 35W setup. Plus, overall light output would be compromised as well. This also does not take into account the current draw on the battery, IPDM/er, fuses, wiring, etc.

Save yourself a ton of potential headaches, get the proper rated bulbs.

 

I was afraid of that, when I first put them in the driver's side wouldn't stay lit in accessory mode, but with the car running it was fine. Hopefully the place I bought them from will take them back., I don't want to throw $75 down the drain.

 

This is due to the battery not having enough current to maintain the ballast whereas with the engine running the alternator increases output to meet demand- to a limit.

Good luck!