99TAVert

Went to start wiring this guy last night and it seems like I have a lot more wires than the Metra 70-1858 has on it.

Will it even work with the amp or am I better off bypassing?

looking at the wiring diagram on AllData it looks like the factory amp is more of a booster than an amp as I see splices in every speaker lead versus a traditional line level input.

Also the factory harness has the bare drain wire, right and left audio signal wires etc and the Metra is blank on these spots.

VIP1

There are 2 connectors on the factory radio. One is for the speakers and amp. The other is for the CD Changer. The Metra Harness if only for the speakers and amp.

WhiteBird00

iTrader: (4)

Certainly the Metra adapter harness will work with the Monsoon amp. In fact, the Monsoon system is one of the easiest factory amplified systems to upgrade head units.

As VIP1 has mentioned, there are multiple connectors at the radio head unit. The factory configuration has three connectors but aftermarket harness adapters such as the Metra combine the two main 10-pin connectors into a single 20-pin connector. Then there is an additional 9-pin connector for the optional remote CD changer. All Monsoon systems have that extra harness and connector even if the CD changer is not there (it is the one with the bare drain wire). You cannot use that connector with an aftermarket head unit since no currently available aftermarket HU supports the GM changer. Just leave it unplugged and you will be fine.

Yes, in effect the Monsoon amp is a booster in that it takes speaker level input but it does a lot more than that because it has eight channels of output with signal filtering specific to the types of speakers used in the doors, sail panels, and hatch area. Bypassing the Monsoon amp would be a silly thing to do. Why give up the added power if you don't have to?

Please have a look at the Monsoon FAQ sticky. It answers all of these questions and a lot more.