It's not a matter of the optical drive cable vs. the hard drive cable. It's a matter of what technology the cables use. For example, SATA II is faster than SATA I. If you've got a recent Mac, your optical drive and hard drive cables are most likely running the same speed SATA and are therefore interchangeable.
There are models of the battery that are compatible with both years. The battery we sell is one of those: MacBook Pro 13" Unibody (Mid 2009/Mid 2010/Early 2011/Late 2011/Mid 2012) Battery
When the accessory power is on or the car is running, the Remote to Ground connection should measure 12V. If there's a negligible voltage coming from the source of the remote wire, that's probably the issue - especially if the problem persists with different amps including a brand new one. Have your sister check the connection of the remote power cable.
I'm not positive, but you probably need an OBDII reader of some kind. I have one that plugs in to my iPhone and uses an app called "DashCommand" to read and clear codes and warning lights, but there are many standalone units that also will solve your problem.
iFixit sells an Optical Drive Enclosure for your MacBook Core 2 Duo. This lets you add in a second hard drive in place of the optical drive. Most of us here have that and we love it!
My initial guess is the heat sensor. It tells the dryer when to kick on the gas. However, if it's only getting warm, perhaps you have a problem with the amount of gas coming in (too little). Check that the gas valve is open all the way. If that's good, you might have blockage in the exhaust vent. Check to make sure it's clear. [Source: I've had both of these problems.]
Hi pfhannan, Thank you for your post. Unfortunately, we do not sell the parts for the Mac Mini model that you are looking for. If you have any further questions, feel free to email support@ifixit.com.