Rearview mirror button and mirror opening measurement question/issue (Page 1/2)
Trinten JUL 09, 08:25 PM
What do you guys measure the width of the rearview mirror button at the widest point in your cars?
And if you use the 'blade' side (opposite side from the 'pinchers') what is the opening at the base of the your rearview mirror, inside the channel where the button would go?

When I had my new windshield put in a few years back, they said they put in a Fiero 'button'.

I couldn't find my rearview mirror, so I ordered a used one from the Fiero store. It arrives. It won't slide on. It barely starts (there's no screw in it). I tried using a little force, but I don't want to crack my windshield.

Perplexed, I use calipers to measure the width of the button at it's widest point: 0.975.
I use the 'blade' side of the calipers to measure the opening of the rearview mirror I got from TFS at the opening: 0.902. Well, that certainly is an issue.

Fast forward a bit, I'm in the junkyard getting parts off an '88 Fiero. It has the mirror in there, though it's in BAD shape. However, still good for measurements!
Junkyard button: 0.98
Junkyard mirror opening at it's widest point: 0.966
This is closer and makes sense, the mirror has to be a tiny bit smaller to help seat securely on the button.

So now I'm trying to figure out - is the parts I found/measured in the junkyard aftermarket, or did I get some oddball mirror from TFS?

I couldn't find any info on this in my searches. So thought it might be useful for others as well as myself. I did find a Dorman replacement rearview mirror (part 76502) that says it uses a 0.98 wide button, so I am going to order that and see if it works.
buddycraigg JUL 09, 09:11 PM
Let us know if it works out.
Vintage-Nut JUL 10, 11:03 AM

quote
by Trinten:
Perplexed, I use calipers to measure the width of the button at it's widest point: 0.975.



From my '88 OEM Rearview Mirror:
Windshield 'Button' at its widest point is 0.970"
Mirror opening for the 'button' at its widest point is 1.0"
Trinten JUL 10, 11:19 AM
Thank you!

Definitely seems to be some variations out there - unless someone sent a non-Fiero rear view mirror to TFS. Maybe I should have bought one of their reproductions.

I did email Dorman for some clarification, because they have another button (part 76975) that is also 0.98 wide at the base, and is listed specifically for the Fiero. So I guess there could be other unlisted differences, such as angle of the "wings" off the button, or the thickness of those.

This could be a not-so-fun game of trial and error. You'd think the automotive industry would be okay with making some parts universal. lol

[This message has been edited by Trinten (edited 07-10-2023).]

John W. Tilford JUL 10, 11:58 AM
I bought a mirror from a junkyard. Took it out of a GM SUV. My original 1988 GT mirror was internally corroded. The GM mirror looked new and offered outside temperature and compass.

Back to your issue: the GM mirror slid on the Fiero mirror mount (glued to glass) with no problem. Tightened easily. GM mirror works great, looks good. $25.

Took me about a day to get the temperature sensor mounted in front of the Fiero radiator and - worse part - run the sensor wire to the mirror. Power is available inside the Fiero overhead light box. I put a miniature switch on the edge of the box.

Hazard: the power inside the overhead light box is "on" all the time. I forgot to turn the mirror power off before a two week vacation once = dead battery.

------------------
John W. Tilford

Trinten JUL 10, 12:07 PM
Thanks John!

That's a great tip. Right now the biggest thing is to find out if it's a normal GM button (that second button part number I listed, does show a wide variety of compatible GM cars and SUVs on the Dorman site), or if it's a Chrysler/VW button (the first part number I listed from Dorman). The next time I'm at my buddy's house I might kidnap his Fiero mirror and see if it slides onto my button or not. That will help eliminate the question about what base is in my car.

I don't know why I didn't think of that sooner... it's been a long month.

css9450 JUL 10, 12:08 PM

quote
Originally posted by John W. Tilford:

Hazard: the power inside the overhead light box is "on" all the time. I forgot to turn the mirror power off before a two week vacation once = dead battery.




LOL I did that too! I had to charge the battery after a few days of it showing "N" on the compass.

I'm using a Cadillac compass mirror in my car. It's from the junkyard...... No temp though.
theogre JUL 10, 04:56 PM
Size/Shape of "Button" on glass depends on Year.
Think is 86⬇️ vs 87⬆️
The ⬆️ Mirrors won't fit ⬇️ Button and other way around.

Believe Is also why when order new windshield what to know what year car because Button are attach at glass maker.
They use way stronger "glue" that you or most glass dealers can get and prepare the both better too so won't fall off often in months.

If have right mirror for the car... Likely have replace the glass for "wrong" year.
If because TFS likely send wrong mirror.

------------------
Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave

Trinten JUL 10, 05:07 PM
Thanks Ogre!
That's crazy that Pontiac/GM even changed the freaking rearview mirror / base over the years.

I'm going to keep my fingers crossed that the Dorman mirror works. Mike's Fiero is also an 87, so that'll be a good test as well. If neither work on the exiting button, it looks like the Dorman mirror comes with the button for that mirror - I guess I'll need to use the epoxy/glue to marry the buttons together and put the mirror on that way.
Trinten AUG 21, 08:20 PM
Just a quick follow up on this -

I took the used mirror I bought from TFS and it would not fit on Mike's 87 windshield mounting button either. Unsurprisingly, his mirror did not fit on mine.

So this goes back to what Ogre said, if PGW was putting buttons on the glass at the factory, then this is a windshield for another year Fiero, likely an earlier year.

So I still am going to try to hunt down an aftermarket or NOS 86 Fiero rear view mirror and see if that works, if not, I'll take John's path and get a few different GM ones from a junkyard to see if any of them fit.

Last option... do the "double button" solution, and glue the 'right' button on top of this one. *sigh*.