Oil Change Indicator & Rear View Mirror Q's

Thunderbird83

Registered User
Hello all,

New owner here... I just bought a 1991 Thunderbird SC. It's a decent car, originally from Florida.

I'm working on fixing a few minor problems (ABS accumulator, misc. bulbs, etc.), but I have a couple of items that have me curious...

What should be showing up on the Oil Change computer (above the radio)? Mine is completely blank. The car has an aftermarket stereo system and CD changer, and it looks like the original CD player in the dash has been disconnected. Did they also disconnect the oil change computer, or is it supposed to be blank unless it needs to tell me something?

Second question... the car has an auto dimming rear view mirror installed, but it isn't plugged in to anything (and therefore is non-functional). What is it supposed to be plugged in to, and how can I tell if the car came with this mirror or if it was swapped out later?
 
Last edited:
If I have time before the shootout, I will be adapting my 89 to accept a much newer (non-T-bird) model autodimming mirror (with compass/outside temp?), but I haven't looked at it for a couple of years now.

I can scan and post wiring diagrams for the 89 and the 93 - I'm not sure where the 91 falls with the autodimming mirror though - but I do know the change occurred somewhere in there - my guess would be 92.

The key is finding the right diagram for the new mirror. :rolleyes:
 
The oil change and fluid level computer (Vehicle Maintenance Monitor, or VMM) should not be blank. Perhaps they accidentally unplugged it or cut a wire while dealing with the stereo.
 
The oil change indicator, more commonly known as the VMM (Vehicle Maintenance Monitor) is split into 2 sections - left side shows if oil is OK, Change Soon, or Now. The right side shows Oil, Fuel, Radiator, and Washer and if any of them get low, "low" will appear next to whichever one is low.

I don't have a picture handy, but you may be able to search the forum to find a picture or someone else may have one.

-Melon

EDIT: Haha looks like I type slow :D
 
It's possible that the actual electronics fell back into the opening and left the faceplate there too. Not likely, but I've had it happen! :eek:
 
Thanks for the replies... So how do I remove the VMM to see if it is hooked up? Is there a special tool that needs to go in the little tabs to get the unit out?
 
I'll take any extra credit I can :) Is it transferable to my girlfriend to make up for when I make her mad? :p

-Melon

Mmm .. probably not.

Thunderbird83 said:
Thanks for the replies... So how do I remove the VMM to see if it is hooked up? Is there a special tool that needs to go in the little tabs to get the unit out?

Two small screwdrivers should do it.
 
Do I just pry it out? Is there a tab that gets released when I put a screwdriver in the holes? It sounds like I'm cracking something when I just put a little pressure on it.

[[ this example is for early models ]]

Just pry it straight out...even on both sides. It should pop/slide straight out. As mentioned, two small flat-bladed screwdrivers should work...anything that fits nicely into each slot on the sides and allows you to pry the unit out.

There are two spring clips that hold it in on the sides - the only thing you need to watch at this point is to not scratch up the bezel sides or the area around it when using tools to pry it out.

There should be a multi-wire connector attached to the center, rear and enough slack in the harness to let you work - push down on the small tab on the wiring connector first, then pull the connector away.

If you decide for whatever reason to open the unit, be very careful not to break the plastic tabs on the housing.

I'm sure someone can sell you another if you need it. There are two different types (reset button versus hole for probe) and either will work. I had to replace mine and made up one unit from spares that has the button, no broken tabs and no scratches :)
 
If the tabs are already broken (very possible) then it can be a little trickier getting it out. You'll need to pry the retaining spring clip things towards the center of the VMM - you might even be able to see them depending on how loose your VMM fits. They are stainless steel.
 
attachment.php


If the tabs are already broken (very possible) then it can be a little trickier getting it out. You'll need to pry the retaining spring clip things towards the center of the VMM - you might even be able to see them depending on how loose your VMM fits. They are stainless steel.

Good point.

I've had to work one side, then the other (not straight out) in that case.

I found one that someone wrapped in elect. tape and then stuffed back into the hole. It worked...sort of. Tabs were broken, etc. so the tape was doing double-duty by holding the unit together and keeping it in the hole in the dash.

A bit like the one in the photo below

Seems like at least half of the ones I find are busted up in one way or the other...
 

Attachments

  • VMM_old.jpg
    VMM_old.jpg
    57.3 KB · Views: 108
Last edited:
Finding out about this car of mine is like peeling an onion...

Mystery solved (somewhat). I pulled the unit out, only to discover that the reason it was blank was because the faceplate had been disconnected from the "guts" of the unit. The faceplate was lightly glued in, with the guts lying loose behind it. The guts had the display and the unit, and it appears to be plugged in (although there wasn't enough slack to pull it all the way out to fully inspect it).

My guess is that it was disconnected to install the radio, and perhaps the mounting and faceplate was broken in the process. The unit itself is probably non-functional, although I'm baffled as to why they left it in there plugged in and loose.

VMM toast. It's really just eye candy, right? Perhaps I'll buy a replacement someday... For now, I can re-focus my attention on hooking up the rear view mirror.
 
Back
Top