October 2016
Today upon arriving at a family get-together the rear hatch decided it wasn't going to open. The door switches and the console switch all stopped working. I needed to unload the stuff in the rear compartment so I used the emergency pull-cord to release the hatch. It's a little tough to get to when the rear compartment is full of stuff.
When I got home, I noticed that I could hear the hatch relay clicking but the hatch solenoid didn't activate. After removing the plastic trim to access the solenoid I was able to test a few things and found that all systems up to the solenoid checked OK. So I applied 12 volts directly to the solenoid and it was indeed dead. When I ohm'ed the solenoid it appeared to be an open circuit.
A search of the internet showed that the solenoid had been discontinued and no one had any in stock. A few used ones were available on eBay for around $40 to $70.
Solenoids are usually pretty robust devices so unless the windings had burned up I figured it might be repairable.
A search of www.CorvetteForum.com returned a thread describing how to repair the solenoid:
15 cent rear hatch solenoid repair
I followed the instructions and opened up the solenoid casing with a flex-shaft tool and a small cut-off wheel.
Once the solenoid was opened, I found a solder joint that was nothing more than a blob of solder sitting on top of one wire while the wire underneath wasn't soldered at all. It's amazing to me that the solenoid ever worked.
The solenoid coil looked fine and the plunger moved freely. A quick measurement with my digital multi-meter showed a coil resistance of 1 ohm.
I cleaned up the solenoid coil and housing, repaired the bad solder joint, added an external ground lead to the solenoid coil (as suggested in the CorvetteForum thread) and reattached the plastic end-cap with Epoxy. Now that the design deficiencies have been corrected, I suspect that I may never have to touch this part again.
So in my case, it wasn't a bad internal ground (as described in the CorvetteForum thread) causing the problem, it was a bad solder joint.
As a side note: when I removed the plastic trim to reveal the hatch solenoid I found evidence of mouse activity. It looked like the mouse had gathered some carpet padding fluff and chewed on the foam rubber padding near the rear hatch latch. I found a couple of wires that had electrical tape wrapped around them and when I removed the tape it was pretty clear that the insulation had been chewed off. The wire was fine but the insulation was missing. One of the car's previous owners must have dealt with this. I vacuumed the mess up and re-insulated the wires.
Also, I found that a previous owner had unplugged the rear hatch cargo light switch. I have no idea why this was done. I reconnected the cargo light switch and it worked. I never noticed that the cargo lights didn't work independently of the other interior lights. But now they do.
Such are the things you find when working on an old car.