I was poking around Steve Millen Autosports' web site (www.stillen.com) and in their accessories for GMC Jimmys, I found a pretty nifty accessory there for sale. It was an inside rear view mirror with a digital compass and outside temperature indicator, not to mention map lights. Well, that was nifty enough that I asked for it for Christmas, and I got it in 1998.
I checked out the instructions, and it appeared that the mirror may have been one that some of the original features didn't work on. It came with two remote keys, and the instructions included hookup to electric door locks. However, the harness didn't have those wires. The instructions also were for a Suburban, which is a much bigger vehicle than my Jimmy.
Well, I've built stuff without instructions before, and everything I wanted and more seemed to be there. I went to Orvac Electronics in Fullerton,CA, and bought about 20 feet of wire loom. That is a corrugated plastic tube with a slit all along it. I bought that much because I wanted to do some preliminary work on fog lights as long as I was poking holes in the firewall and running new wires in the dashboard. Just about all of the 12V wiring under the hood is in that loom, and I wanted this installation to look professional.
The temperature sensor is mounted to the inside edge
of the front frame fork. It is under the radiator, behind the air dam.
If the car is sitting still, it will pick up a little heat from the
engine, but it's lower than the block so it really doesn't affect the reading
unless it's just been sitting in a parking lot for an hour. The
instructions said to mount it to the radiator shell, but mine looked different
than the instructions described, so I went a little astray.
The instructions also said to run the wiring harness to the passenger side of the truck, through an existing hole in the firewall, up the windshield pillar and inside the headliner to the mirror. Part of the harness was to go behind the dashboard to the fuse block. Wrong instructions, wrong car again. As far as I can tell, there are two reasons for routing the harness this way. There's already a hole, and that's where the harness can connect to the electric door locks. In the Jimmy, there's no hole (and no room to put one, either!) and the harness doesn't have the wires for the door locks. Again, I went a little astray.
I ran the wire loom from the frame fork to the left
of the truck, behind the headlight and under the oil filter and windshield
washer reservoir. As long as I was doing that, I also did it with the
loom for the fog lights. I used a Greenlee chassis punch to make two
holes in the firewall that went into a cavity that has the door hinges and
not much else. Inside the truck, you can get to that cavity by taking
off the driver's kick plate and removing a piece of insulation that's held
in place by reusable adhesive. I lined the holes with grommets and
pushed the loom through. I located the dome light connection. The
harness came with an excellent connector that fit between the existing
connectors, so that was a snap. The connection to the fuse block was
a slightly different issue. GM uses special crimp-on connectors for
this block, and this didn't come with one. My connector kit revealed
several crimp-on lugs, though, and one of these fit and seems to be working
just fine.
Then I had to run the wires up the driver's side windshield pillar. This is where the wiring for the stock rear view mirror's reading lights already ran, and there's enough room under the cover for quite a bit more wiring, if I'm ever tempted to add more electricity to the roof of the truck. The tricky part was getting the wiring from under the dash up to that spot. I was able to force the wiring (one wire at a time) between the edge of the dash and the body of the truck with a large flat blade screwdriver. Once I got through there, the windshield pillar didn't present any problems.
In order to run the wiring from the pillar to the middle of the headliner, I had to take off the drivers sun visor. It's just held on with three screws, so that was pretty easy. I tucked the wiring up far enough so there were no bulges in the headliner.
The mirror itself mounts to the same piece of metal
that the stock mirror mounted to. That piece is glued to the windshield.
The locking screw has that crazy little GM spline head, but fortunately
I have the tools for that.
I stuck the insulation back over the door hinge cavity, put the kick plate back on, and replaced the sun visor and the windshield pillar cover. When I fired everything up, one of the reading lights didn't work. It was a burned out bulb, and they're not all that easy to replace, but it's in there now.
The compass required calibration. The calibration technique is to drive around in circles four times. After doing that, it tells me which direction I'm pointed in with an eight point compass (N, NE, E, SE, S, SW, W, NW), and the temperature indicator seems to be within a degree of the billboards that also show the temperature, so I'm pretty sure it's working well.
Once I had everything working, I sealed up the hole in the firewall with RTV adhesive.
This mirror is quite a bit heavier than the original one, and the adhesive that holds the mounting plate to the windshield let loose once. This isn't the first car I've had where the rear view mirror fell off the windshield, so I'm a little concerned about that happening again. It's a real pain to drive around with the mirror dangling from its wiring.
The bracket side of the original glue is what came loose, and the glue seemed stuck to the windshield quite solidly, so I decided to try gluing the bracket back to the original glue with 5 minute epoxy. So far, it seems stuck. However, when I did that, some of the epoxy seeped into the groove where the mirror actually mounts to the plate. I didn't notice that when I re-installed the mirror. A few weeks later, the mirror popped off the bracket. I didn't know what was going on, but when I checked carefully, I noticed the epoxy in the groove. I cut it out with a utility knife with about half an hour's work. I also noticed that the mount for the mirror is a little different from the mount for the original. It's tapered a little, and about 1/8" wider at the bottom than the original. I don't think this will cause any trouble at this point, because the top half of the mirror is firmly in the groove, and the set screw is holding everything in place.
I would get the exact mounting plate and put it on with 5 minute epoxy. I'd make sure the grooves were clean before I put the mirror back on and drove around.
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