Thread: rear view mirror meltdown

In too much heat, the fluid in the auto dim can burst and leak. It does happen.

Try ebay for a good used part or post a wtb thread in the classified section of the forum.

The Grand Prix' that came without the OnStar Gentex self dimming mirrors got the Donnelly self dimming mirrors instead, and Donnellys are junk. They're notorious for breaking/leaking. Gentex was the first company to introduce self-dimming, and they use electro-chromic technology which is a gel that darkens with an electrical charge. Donnelly uses something similar, but for some reason, the gel or liquid they use seems to be a lot more unstable. The only downfall to Gentex is if you need map lights on them, they're much harder to come across. If you don't care about that, I highly suggest you switch to Gentex. I have a few different kinds of those. If you want to stick with the Donnelly, I've got a few extras laying around of those as well. I'd sell you one for $60 shipped, and I always test my mirrors prior to selling them.

So if it has OnStar it's a Gentex then right?
Also, since the plug is different between the two, is there a way to make one of the newer onstar ones work in an older GP that didnt have onstar?

Yes, if it's OnStar, it's Gentex. I believe they have an exclusive with GM for it. But if your car didn't come with OnStar, I wouldn't bother or mess with adding an OnStar version. It has a TON of wires which you will have no use for vs. a simple 2-wire operation. This is why OnStar mirrors don't sell for jack compared to regular ones. You either already have one, or you don't want one. Just get a regular Gentex self-dimming with compass. If you want one with temp as well, they made those well before the OnStar mirrors, too.

Well I'm not concerned about actually making the onstar function, but I THINK my current mirror is a 3 pin, I just want to be able to make the auto dimming work. Is the one with the compass a 3 pin?

Yeah, I wasn't suggesting that you'd want to make the OnStar work. For starters, it would be useless as our generation of GPs had analog OnStar which literally no longer works since they went digital signal several years back. You'd have to rip out an OnStar receiver from a newer GM. Secondly, even if it worked, it would be a serious pain in the ass to wire everything in for it. The OnStar mirrors have something like a 20+ pin harness. But even if you wanted to just use the self dimming and compass, you'd only have 2 wires going into that 20+ pin harness, not to mention it's a very big, bulky mirror which looks ugly to me. In fact, if I wouldn't have a couple dozen wires to hide or get rid of, I'd switch to a regular Gentex myself since the original OnStar is useless and obsolete now.

The newer mirrors use a 7 pin harness (Gentex started using them several years before Donnelly), but since you already have a self-dimming mirror, it would be VERY easy to just splice it into your pre-existing wires for your current mirror. You already have everything you need; 1 wire running to a 12V+, 1 wire running to a - ground. Otherwise, to go with a 3-pin Gentex mirror, you'd have to go with an early - mid '90s style mirror which won't look right with the newer interiors.

Do I just get one of the $70 one's from amazon then?

The only one I see for $70 on Amazon has no compass. If that doesn't matter to you, then that should be fine, though I'm wondering if that's the newest style mirror or what, because it doesn't look like any Gentex I've seen before. You may want to contact the seller and make sure it comes with the harness, too.

Otherwise, I have plenty of the self-dimming without compass Gentex mirrors I could do for $50 shipped. With compass = $70 shipped.

Does the compass need to be wired separately, or is it all just 2 wires?
Either way I'll get back to you on this one for sure.

The single + wire powers the self dimming as well as the compass. The compass is self contained, so no additional wires are needed.