Answer: The G320 ground. How is this you say? Right where the L/H hatch drain hole is drilled...... Yep! The ABS harness runs up to the L/H halo for routing and its ground. When I drilled the hatch drain the drill severed BOTH grounds for the ABS relay module and pump/controller! Just missed getting the whole ABS bundle!

What luck! I need to go to Reno for Hot August Nights and hit the Casinos this weekend.

So in retrospect; I checked the DIC for good bulbs then followed the service manual troubleshooting guide. The first check was measuring power across the four points of the relay module. This where the missing ground was discovered.

Why, oh why, didn't the MAD drain kit discuss the harness routing?
Why did GM put the fuse for the rear hatch behind the DIC?

Why does it always seem to take 12 hours to do a one hour job?

Thanks for everyones help.
Coming up next, bias spring report.

-JRC-

With as much wiring as C4s have, if you start drilling holes in them you're bound to hit something!

Yeah, I thought it stupid to put ANY fuses behind the DIC...guess they figured they'd put the THEFT there, because no one would look there to disable the factory alarm.

Glad you found the problem

Cool! It sucks when you have mind-bending problems like yours, but when you figure them out it makes you feel good!

Yeah, when I tried to install my hatch drains, the first hole I drilled was at the wrong angle and I ended up hitting a metal body panel mounting support. Got the hole through the first layer of fiberglass in the channel, then couldn't get the drill bit through the second layer (because unbeknownst to me, it was hardened steel). So I said "Screw it", stopped right there, and had one big hole in the side of my car. Well, the next couple of days it rained, and my car sits outside so it got rained on. I come out one morning to open the passenger door and get something out of the car when I notice that the gray carpet looks very dark in the footwell. The carpet was soaked from the footwell all the way to behind the seat. Turns out that because I had a hole in the top of the fiberglass and no drain hole underneath (well, I had the pilot hole), when the water started flowing through there at a rate faster than it could drain back out, it decided to make it's way between the layers of fiberglass and dump out into the interior, down the sloped panel behind the seat. So basically I now had a gentle waterfall behind my passenger seat. I was not pleased. Right now I have an Admiral Blue piece of electrical tape (not really, but a close match nonetheless) over the hole and it has managed to keep the water out. Eventually I'll get some silicone and fill the hole, then paint the top with touch-up paint.

So the hatch drain kit gets a big thumbs down from me.

Hammerdown your experience sounds much worse than mine. The kit install required a bit more planning and work than the instructions called for. I am sending MAD an email requesting they add a note to thier instrution pack. With luck, another Vette owner will not have to suffer our fates. BTW I hit the edge of the steel plate you refer to as well. Will post or write up the proceedure for a Tech Tip soon.

-JRC-

Note to self: Do not drill on my C4. WOW, that was some picture. One thing about trouble shooting, you tend to know the system better than when you started.

A friend once told me he tried to install some speakers in an MG. Found a good spot behind the seat, started drilling, and noticed gasoline coming out the hole. He then did some system diagnosis and found out exactly where the fuel tank was located. Not sure if he sold his new speakers. Had to buy some JB weld or something like that.

Oh well.

Glad you found the problem.

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I also sent MAD an email "suggesting they include a note indicating the possible location of a wiring harness there. They probably think I'm just some Goober with a drill and no cents. Oh geez, maybe I am?

-JRC-

Jeebus! Did you drill that hole with a sawzall?

Yeah, those hatch and alarm fuses are all located behind the DIC for security reasons. I mean, what's the point of an alarm if it can be turned off by pulling an easy to reach fuse?

Yeah, there's a law of physics that states: If you have one 1/8" wire running in an 8" conduit, if you drill a 1/8" hole in the conduit you have a 99% chance of severing the wire.

I believe that it's a corollary of Murphy's law.

We lost our LAN to that once...

I'm familiar with that one. I had considered putting the drains in, but will continue to just use blower to get the water out of that corner. Thanks to all for the info!