Ethernet problem after hard drive upgrade in early 08 IMac

I have a 24" early 2008 iMac 2.4ghz machine that had a hard drive failure last week. After replacement, I loaded the original leopard os, then snow leopard, and then straight to Mavericks. Loaded my Time Machine backup after that. Updated all other software last. Everything went great. But during the whole install, My ethernet would not connect. Not just with Mavericks. WiFi works great. Tested cable and router on another machine. all good. In network settings, my ethernet has no ip address. Reset all equipment with no results. Ran AHT and all hardware tested good. Any ideas?

Sounds like a hardware problem. Check System Information to see if Ethernet still recognised. Is the WIFI internal or USB Adapter.

In system info, this i what pops up. So I take that it is recognized. Also, WiFI is internal

Marvell Yukon Gigabit Adapter 88E8055 Singleport Copper SA:

Name: ethernet
Type: Ethernet Controller
Bus: PCI
Vendor ID: 0x11ab
Device ID: 0x436a
Subsystem Vendor ID: 0x11ab
Subsystem ID: 0x00ba
Revision ID: 0x0013
Link Width: x1
BSD name: en0
Kext name: AppleYukon2.kext
Location: /System/Library/Extensions/IONetworkingFamily.kext/Contents/PlugIns/AppleYukon2.kext
Version: 3.2.3b1

In your System Preferences -> Network and click the "Assist Me" -> Diagnostics and follow their prompts and any directions they supply.

You may need to actually power down your modem etc., wait 20-30 seconds and then power it back up again and any other networked devices.

Let each one get established with proper lights showing before powering up the next one, and then finally power up your Mac.

This is assuming that you're using DHCP addressing.

Powered down and rebooted in the order you suggested. No result. In the diagnostics, The ethernet fails, But I noticed it alternates from red to green, like it tries to recognize it, but seems to be pulsing. Does that make sense? Also, could I have done something when I replaced my drive? Ethernet card is internal to mother board right? So, if that is bad, I'm screwed right?

I know this may sound over-simplified, but do you have a spare ethernet cable that you can try? Ethernet cable connectors are infamous for failing. I have had them fail on me numerous times. The cheap plastic push down - up connectors on them sometimes cause the minute wire ends to slip out. Very difficult to spot. (I know you said you tested the cable on another machine.)

Do you get any solid green checks while doing the diagnostics?

i.e.:

Cable is good. Tested another cable and even put cables on a laptop to test. As for the green lights, I get red on ethernet and network settings. On the ethernet one, it actually bounces between red and green like it is pulsing. Does that make sense?

The only sense it makes is that it's saying it's not working properly!!

Did you do the HDD replacement yourself??

Were all interior cables reconnected properly and firmly???

I'd have to check were the E'net cable is on that Mac, but I'd suspect it isn't connected properly or firmly.

Bummer eh??

I might check tomorrow about the location of that cable if I remember.